Books
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Sexual selection: perspectives and models from the Neotropics
Edited by Regina H. Macedo & Glauco Machado (2013) Published by Elsevier Review
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Harvestmen: the biology of Opiliones
Edited by Ricardo Pinto-da-Rocha, Glauco Machado & Gonzalo Giribet (2007) Published by Harvard University Press Award
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Reviews
Book chapters*
11. Machado, G., Trumbo, S.T. 2018. Parental care. In: Insect behavior: from mechanisms to ecological and evolutionary consequences, Edited by A. Córdoba-Aguilar, D. González-Tokman & I. González-Santoyo, pp. 203–218. Oxford: Oxford University Press.
10. Machado, G., Requena, G.S., Gadea, C.T., Stanley, E., Macías-Ordóñez, R. 2015. Male and female mate choice in harvestmen: general patterns and inferences on the underlying processes. In: Cryptic female choice in arthropods: patterns, mechanisms and prospects, Edited by A.V. Peretti & A. Aisenberg, pp. 169–201. New York: Springer.
9. Buzatto, B.A., Macías-Ordóñez, R., Machado, G. 2013. Macroecology of harvestman mating systems. In: Sexual selection: perspectives and models from the Neotropics, Edited by R.H. Macedo & G. Machado, pp. 115–162. Amsterdan: Elsevier.
8. Macías-Ordóñez, Machado, G., Macedo, R. 2013. Macroecology of sexual selection: large-scale influence of climate on sexually selected traits. In:Sexual selection: perspectives and models from the Neotropics, Edited by R.H. Macedo & G. Machado, pp. 1–32. Amsterdan: Elsevier.
7. Requena, G.S., Munguía-Steyer, R., Machado, G. 2013. Paternal care and sexual selection in arthropods. In: Sexual selection: perspectives and models from the Neotropics, Edited by R.H. Macedo & G. Machado, pp. 201–234. Amsterdan: Elsevier.
6. Macías-Ordóñez, R., Machado, G., Pérez-González, A., Shultz, J.W. 2008. Genitalic evolution in Opiliones. In: The evolution of primary sexual characters in animals, Edited by J.L. Leonard, A. Córdoba-Aguilar, pp. 285–306. Oxford: Oxford University Press.
5. Acosta, L.E., Machado, G. 2007. Diet and foraging. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 309–338. Massachusetts: Harvard University Press.
4. Curtis, D.J., Machado, G. 2007. Ecology. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 280–308. Massachusetts: Harvard University Press.
3. Machado, G., Macías-Ordóñez, R. 2007. Reproduction. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 414–454. Massachusetts: Harvard University Press.
2. Machado, G., Macías-Ordóñez, R. 2007. Social behavior. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 400–413. Massachusetts: Harvard University Press.
1. Machado, G., Pinto-da-Rocha, R., Giribet, G. 2007. What are harvestmen? In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 1–13. Massachusetts: Harvard University Press.
10. Machado, G., Requena, G.S., Gadea, C.T., Stanley, E., Macías-Ordóñez, R. 2015. Male and female mate choice in harvestmen: general patterns and inferences on the underlying processes. In: Cryptic female choice in arthropods: patterns, mechanisms and prospects, Edited by A.V. Peretti & A. Aisenberg, pp. 169–201. New York: Springer.
9. Buzatto, B.A., Macías-Ordóñez, R., Machado, G. 2013. Macroecology of harvestman mating systems. In: Sexual selection: perspectives and models from the Neotropics, Edited by R.H. Macedo & G. Machado, pp. 115–162. Amsterdan: Elsevier.
8. Macías-Ordóñez, Machado, G., Macedo, R. 2013. Macroecology of sexual selection: large-scale influence of climate on sexually selected traits. In:Sexual selection: perspectives and models from the Neotropics, Edited by R.H. Macedo & G. Machado, pp. 1–32. Amsterdan: Elsevier.
7. Requena, G.S., Munguía-Steyer, R., Machado, G. 2013. Paternal care and sexual selection in arthropods. In: Sexual selection: perspectives and models from the Neotropics, Edited by R.H. Macedo & G. Machado, pp. 201–234. Amsterdan: Elsevier.
6. Macías-Ordóñez, R., Machado, G., Pérez-González, A., Shultz, J.W. 2008. Genitalic evolution in Opiliones. In: The evolution of primary sexual characters in animals, Edited by J.L. Leonard, A. Córdoba-Aguilar, pp. 285–306. Oxford: Oxford University Press.
5. Acosta, L.E., Machado, G. 2007. Diet and foraging. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 309–338. Massachusetts: Harvard University Press.
4. Curtis, D.J., Machado, G. 2007. Ecology. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 280–308. Massachusetts: Harvard University Press.
3. Machado, G., Macías-Ordóñez, R. 2007. Reproduction. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 414–454. Massachusetts: Harvard University Press.
2. Machado, G., Macías-Ordóñez, R. 2007. Social behavior. In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 400–413. Massachusetts: Harvard University Press.
1. Machado, G., Pinto-da-Rocha, R., Giribet, G. 2007. What are harvestmen? In: Harvestmen: the biology of Opiliones, Edited by R. Pinto-da-Rocha, G. Machado & G. Giribet, pp. 1–13. Massachusetts: Harvard University Press.
* The name of current and former lab members are highlighted in bold.
Comments and replays*
5. Buzatto, B., Machado, G., Palaoro, A.V. 2024. Sigmoid allometries generate male dimorphism in secondary sexual traits: a comment on Packard (2023). Evolutionary Ecology, doi.org/10.1007/s10682-024-10303-6. (View) See also the original paper (View)
4. Machado, G., Wolff, J.O. 2017. The assassination of a hypothesis by non-critical interpretation of molecular data: A comment on Sharma et al. (2017). Molecular Phylogenetics and Evolution, 129:346–348. (View) See also the original paper (View) and the rebuttal (View).
3. Ferraz, G., Machado, G., Guimarães Jr., P.R., Koehler, S. 2013. Fundamentos para o conteúdo e a implementação da pós-graduação em Ecologia. Revista Brasileira de Pós-graduação, p. 1–23. (View)
2. Brecovit, A.D., Rheims, C.A., Machado, G. 2005. Encontros de Aracnologia do Cone Sul (1997 - 2003), um investimento de sucesso. Biota Neotropica, p. 1–7. (View)
1. Machado, G. 2002. 3er Encuentro de Aracnólogos del Cono Sur. Boletín de la Sociedad Entomológica Argentina, p. 1–3. (View)
4. Machado, G., Wolff, J.O. 2017. The assassination of a hypothesis by non-critical interpretation of molecular data: A comment on Sharma et al. (2017). Molecular Phylogenetics and Evolution, 129:346–348. (View) See also the original paper (View) and the rebuttal (View).
3. Ferraz, G., Machado, G., Guimarães Jr., P.R., Koehler, S. 2013. Fundamentos para o conteúdo e a implementação da pós-graduação em Ecologia. Revista Brasileira de Pós-graduação, p. 1–23. (View)
2. Brecovit, A.D., Rheims, C.A., Machado, G. 2005. Encontros de Aracnologia do Cone Sul (1997 - 2003), um investimento de sucesso. Biota Neotropica, p. 1–7. (View)
1. Machado, G. 2002. 3er Encuentro de Aracnólogos del Cono Sur. Boletín de la Sociedad Entomológica Argentina, p. 1–3. (View)
* The name of current and former lab members are highlighted in bold.
Papers*
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After each paper, there is a brief description of the main goals and main findings of the study. This summary has been written for a broad audicence, including non-scientists that are interested in behavior and evolution. Each summary, called "In a nutshell", has up to 75 words and if you want to know more about a given work, you can download the pdf of the published paper. If you have any suggestion or criticism about the studies, please contact us.
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* The name of current and former lab members are highlighted in bold.
2024
115. Grossel, L.A., Werneck, R.M., Machado, G. 2024. Effects of nest-site availability on male–male competition and the foraging costs of egg attendance in an arachnid with exclusive paternal care. Ethology, 130:e13511. (View)
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Does nest-site availability influence male-male competition? To answer this question, we conducted a lab experiment manipulating the number of artificial nests provided to a harvestman. Surprisingly, larger males weren’t more likely to hold a nest when this resource was scarce. The small opening of the artificial nests likely enhanced their defensibility, reducing the influence of size on nest ownership. This result highlights the significance of extrinsic factors, such as nest size, in shaping male-male competition.
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114. Goyes Vallejos, J., Sandoval Siles, J., Calero, V., Rodriguez, N., Machado, G. 2024. Not enough time: short-term female presence after oviposition does not improve egg survival in the emerald glass frog. Animal Behaviour, 213:161–171. (View)
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Females of two glass frog species stay close to their eggs for less than 2 hours after oviposition. Surprisingly, this short-term presence decreases dehydration and egg predation. Is this a general pattern in glass frogs? No. Females of the emerald glass frog stay nearly 1.5 hour with their eggs, with no detectable positive effect on offspring survival. Apparently, females improve offspring survival selecting oviposition sites where eggs are moist and hidden from predators.
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113. Machado, G., Burns, M. 2024. Reproductive biology of harvestmen (Arachnida: Opiliones): a review of a rapidly evolving research field. Current Zoology, 70:115–135. (View)
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The book “Harvestmen: The Biology of Opiliones” is 16 years old! After its publication, our knowledge of the reproductive biology of harvestmen greatly increased. This review summarizes the most relevant advances and indicates directions for future studies. Although we have learned a lot about species from the Americas, we still know nothing about species from Africa and continental Asia. If you live in these places, join us in unlocking the mysteries of harvestman reproductive biology.
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112. Alissa, L.M., Machado, G., Requena, G.S. 2024. Good body condition increases male attractiveness but not caring quality in a neotropical arachnid with male‑only care. Behavioral Ecology and Sociobiology, 78:24. (View)
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Females in many species prefer caring over non-caring males. We demonstrated that female mate choice in a harvestman with paternal care is also influenced by males’ body condition. Females prefer caring and non-caring males in good condition over those in poor condition. However, increased body condition doesn’t enhance offspring survival, as predicted by the ‘good parent hypothesis’. We suggest that males in good condition alocate surplus energy to advertise their quality and attract more mates.
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2023
111. Machado, G., Macedo-Rego, R.C. 2023. Benefits and costs of female and male care in amphibians: a meta-analytical approach. Proceedings of the Royal Society B, 290:20231759. (View)
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Many frogs, salamanders, and caecilians care for the offspring. We have compiled information for many amphibian species and demonstrate that parental care enhances offspring fitness, regardless of the caring sex. However, parental care reduces the parents’ body condition, especially if they stay with the offspring all the time. Moreover, parental care decreases the reproductive success of females but not males, probably because females of some species show a mating preference for caring males.
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110. Powell, E.C., Painting, C.J., Machado, G., Holwell, G.I. 2023. Juvenile leg autotomy predicts adult male morph in a New Zealand harvestman with weapon polymorphism. Behavioral Ecology, 34:613-620. (View)
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Have you heard the phrase “your past haunts you”? That’s exactly what happens to males of a New Zealand harvestman. If they are attacked by predators and lose legs during development, they become small adult males that cannot monopolize territories. If they don’t lose legs, they become larger adults that can monopolize territories and attract females. In other words, a past encounter with a predator can compromise their chances of successful mating in the future.
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109. Stanley, E., Machado, G., Aisenberg, A. 2023. Sexual dialogue in Pachyloides thorellii (Opiliones: Gonyleptidae): a Neotropical harvestman with much to say. The Journal of Arachnology, 51:90–100. (View)
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Females and males talk during copulation. Harvestmen obviously don’t talk, but females communicate with males. The rise of the body and the eversion of the ovipositor are clear signs that females are receptive. In turn, sudden backward movement means “I want more stimulation before copulation”. In this paper, we describe for the first time the sexual dialogue of a harvestman species. Although it is hard to understand their idiom, the body language is quite intuitive.
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108. Nyffeler, M., Machado, G., Hartmann, A., Keiser, C.N. 2023. Fungus and fruit consumption by harvestmen and spiders (Opiliones, Araneae): the vegetarian side of two predominantly predaceous arachnid groups. The Journal of Arachnology, 51:1–18. (View)
WARNING: The first author denied me access to the revised version of the manuscript and submitted it to the editor without my consent. Moreover, I did not have access to the page proofs.
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Arachnids are voracious carnivores, right? Humm… not so much. Harvestmen regularly feed on fruit pulp, fleshy seed parts, and fungi. Some of these items are highly caloric, suggesting they are nutritionally relevant. Spiders feed less frequently on fruits, and fungivory is restrict to the consumption of spores trapped in web threads. In contrast with spiders, which are ‘‘fluid feeders’’, harvestmen are ‘‘solid food feeders’’, which may explain the regular consumption of fruits and mushrooms.
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2022
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107. García-Hernández, S., Machado, G. 2022. Short- and long-term effects of an extreme case of autotomy: does “tail” loss and subsequent constipation decrease the locomotor performance of male and female scorpions? Integrative Zoology, 17:672–688. (View) Ig Nobel Winner 2022
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A predator grabs a scorpion’s tai. The scorpion detaches its tail and runs away. Clever, right? However, by losing the tail, scorpions permanently lose the anus and are constipated for life. Here we showed that in the short-term, when tailless scorpions are lighter due to tail loss, there is no change in their locomotor performance. In the long-term, they gain weight and become slower, which may increase their chances of becoming prey in the future.
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106. Palaoro, A.V., García-Hernández, S., Buzatto, B.A., Machado, G. 2022. Function predicts the allometry of contest-related traits, but not sexual or male dimorphism in the amazonian tusked harvestman. Evolutionary Ecology, 36:605–630. (View)
106. Palaoro, A.V., García-Hernández, S., Buzatto, B.A., Machado, G. 2022. Function predicts the allometry of contest-related traits, but not sexual or male dimorphism in the amazonian tusked harvestman. Evolutionary Ecology, 36:605–630. (View)
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What use are those huge spines that males of some harvestman species have on their belly? This question was the motivation of this work. We found that large males aggressively defend cavities in fallen logs that are used as oviposition sites. During the fights, the ventral spines are pressed against the rival, while the contenders remain in a weird belly-to-belly position. Small males don’t fight, have short spines, and invade the cavities to sneak copulations.
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105. Cassettari, B.O., Machado, G. 2022. Pre-copulatory and copulatory courtship in male-dimorphic arthropods. Advances in the Study of Behavior, 54:129–186. (View)
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In many arthropods we find two male morphs that differ in weapon size or degree of ornamentation. But do these morphs also differ in the way they court females? The short answer is yes. However, things are noy very simple: in some species majors court more, while in others minors court more. In this review, we try to make sense of this variation and indicate interesting directions for future studies about this highly neglected subject.
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104. Caldart, V.M., Santos, M.B., Machado, G. 2022. Function of a multimodal signal: a multiple hypothesis test using a robot frog. Journal of Animal Ecology, 91:701–714. (View) Research HIGHLIGHT |
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Some frogs communicate using both visual and acoustic signals. To understand why they do that, we built a robot frog that emits territorial calls and visual signals with their toes, like real frogs. We exposed the robot to males and found that the emission of both signals elicits a more aggressive response than each signal individually. Thus, the combination of signals changes the context of the message, and the way males interact during territorial contests.
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103. Escalante, I., Domínguez, M., Gómez-Ruiz, D.A., Machado, G. 2022. Benefits and costs of mixed-species aggregations in harvestmen (Arachnida: Opiliones). Frontiers in Ecology and Evolution, 9:766323. (View)
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Mixed-species aggregations are an elusive form of social behavior. We revised the cases of mixed-species aggregations in harvestmen, comparing the benefits and costs of this behavior with those reported for single-species aggregations. Moreover, we tested whether harvestmen are more protected from predators and less exposed to mite parasitism in mixed- than in single-species aggregations. We found no difference between the types of aggregations, probably because the membership of the aggregations is very fluid over time.
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102. Castro, J.B.,·Machado, G., Singer, R.B. 2022. Müllerian mimicry between oil‑producing orchids and Malpighiaceae? An old hypothesis finally tested. The Science of Nature, 109:3. (View)
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People think mimicry occurs only in animals, but it’s not true. Plants are considered Müllerian mimics when they have similar floral traits and offer similar rewards to pollinators. Orchids and Malpighiaceae that produce floral oils are hypothesized to form a Müllerian complex. We tested this hypothesis and found that the proximity to a Malpighiaceae does not increase bee visitation to orchid flowers. Thus, floral similarities between orchids and Malpighiaceae are not explained by Müllerian mimicry.
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2021
101. Kury, A.B., Machado, G. 2021. The genus Eurytromma from Sri Lanka: the homology of penial macrosetae in Podoctidae matches the gonyleptoid AE11 pattern (Opiliones: Laniatores: Epedanoidea). The Journal of Arachnology, 49:358–370. (View)
101. Kury, A.B., Machado, G. 2021. The genus Eurytromma from Sri Lanka: the homology of penial macrosetae in Podoctidae matches the gonyleptoid AE11 pattern (Opiliones: Laniatores: Epedanoidea). The Journal of Arachnology, 49:358–370. (View)
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I know it’s a baroque title… Basically, male genitalia in harvestmen have some “bristles”. In 2015, two colleagues (including the first author of this paper) proposed that these “bristles” are arranged in a predictable pattern they called “AE11”. This pattern was well-described for species of neotropical families, and here we show that it also applies to a family distributed mainly in Asia. This finding may help taxonomists to use the “bristles” in phylogenetic studies.
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100. Solano-Brenes, D., Costa-Schmidt, L.E., Albo, M.J., Machado, G. 2021. Differential allocation in a gift‑giving spider: males adjust their reproductive investment in response to female condition. BMC Ecology and Evolution, 21:140. (View)
100. Solano-Brenes, D., Costa-Schmidt, L.E., Albo, M.J., Machado, G. 2021. Differential allocation in a gift‑giving spider: males adjust their reproductive investment in response to female condition. BMC Ecology and Evolution, 21:140. (View)
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Females are usually the choosy sex. However, males of some species can also select their partners. They can either reject or invest less resources in low quality females. Males of a Neotropical gift-giving spider build larger gifts and exhibit longer courtship when paired with females in good body condition. The main reward for the males is that females in good body condition lay 20% more eggs than females in poor body condition.
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99. Macedo-Rego, R.C., Costa-Schmidt, L.E., Machado, G. 2021. Males of a Neotropical spider adjust prey-gift construction but not mate search in response to sperm competition. Ethology, 127:661–668. (View)
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Females of a Neotropical gift-giving spider mate multiple times. When facing sperm competition, males reduce prey-gift quality by depositing less silk on the gift that will be offered to the females. However, when males have access to chemical cues of virgin and once-mated females, they did not bias mate search towards virgin females. These results indicate that males adjust their reproductive effort, but not their mate search effort in response to sperm competition.
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98. Machado, G., Buzatto, B.A., Samia, D.S.M. 2021. It is not always about body size: evidence of Rensch’s rule in a male weapon. Biology Letters, 17:20210234. (View)
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In many species sexual dimorphism increases with body size when males are the larger sex but decreases when females are the larger sex, a macro-evolutionary pattern known as Rensch’s rule. Although most studies focus on body size, Rensch’s proposal included differences in other sexually selected traits. Indeed, the length of the hind legs, used as weapons in male-male fights in harvestmen, follows Rensch’s rule, suggesting that sexual selection is the mechanism underlying the pattern.
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97. Powell, E.C., Willmott, N.J., Selleck, C.J., Painting, C.J., Hickey, A.J., Machado, G., Holwell, G.I. 2021. No risk to scrambling? Mating tactic does not affect the frequency of leg autotomy in a New Zealand harvestman. Animal Behaviour, 177:99–106. (View)
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If your enemies are sit-and-wait predators, the more you move, the higher the predation risk. Males of a harvestman species have two mating tactics: majors defend territories while minors search for females. Thus, minors should be at higher risk of predation. We used the frequency of leg loss to estimate predation pressure on males. Surprisingly, we found no difference between morphs. Perhaps most of the attacked minors simply do not survive to tell the story…
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96. Powell, E.C., Painting, C.J., Hickey, A.J., Machado, G., Holwell, G.I. 2021. Diet, predators, and defensive behaviors of New Zealand harvestmen (Opiliones: Neopilionidae). Journal of Arachnology, 49:122–140. (View)
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New Zealand is an amazing place with an amazing harvestman fauna. Here, we provide natural history information on several species of a diversified harvestman family that inhabits forests. Individuals feed on dead and live prey, and include vegetal matter in their diet. Their main predators were spiders and introduced mammals. The most unexpected predator was an amphibious climbing fish! To cope with predators, individuals show several types of defenses, including death feigning and loosing legs.
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95. Rojas, A., Muniz, D.G., Solano-Brenes, D., Machado, G. 2021. Nest-site selection in a neotropical arachnid with exclusive male care: proximate cues and adaptive meaning. Ethology, 127:334–341. (View)
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Males of a neotropical harvestman build nests on fallen logs and care for eggs laid inside them. Nests located in inadequate sites expose males and eggs to dangers. Thus, males build nests where they are protected from impact of raindrops, the water flow on log surface is low, and the risk of flooding is low. This selection minimizes the risk of nest destruction, decreases egg mortality, and increases male attractiveness because females avoid damaged nests.
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94. García-Hernández, S., Machado, G. 2021. Fitness implications of nonlethal injuries in scorpions: females, but not males, pay reproductive costs. The American Naturalist, 197:379–389. (View) Ig Nobel Winner 2022
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Some animals voluntarily detach body parts to escape predation. However, the missing part may have important functions, including reproduction. Scorpion males use their tail to court females and to help spermatophore transference. Despite that, tail loss has no negative impact on their reproductive success. For females, tail loss and the subsequent constipation reduce their longevity and fecundity, probably because of feces accumulation. Thus, the reproductive costs of tail loss are clearly sex dependent.
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2020
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93. García-Hernández, S., Machado, G. 2020. ‘Tail’ autotomy and consequent stinger loss decrease predation success in scorpions. Animal Behaviour, 169:157–167. (View) Ig Nobel Winner 2022
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Autotomy is the self-amputation a limb in response to a predation attack. Although autotomy increases the chance of survival, it imposes costs to the autotomized individual. We investigated if autotomy impairs predation success in a scorpion that sheds the last abdominal segments, where is located the stinger used for venom inoculation. Stinger loss reduced subduing success and increased handling time of both small and large prey, indicating that tail autotomy imposes foraging costs.
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92. Millan, C.H., Machado, G., Muniz, D.G. 2020. Within-population variation in female mating preference affects the opportunity for sexual selection and the evolution of male traits, but things are not as simple as expected. Journal of Evolutionary Biology, 33:1579–1592. (View)
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A widespread assumption in sexual selection studies is that all females in a population have the same mating preferences. However, this is not always the case. If mating preferences vary between females, what are the consequences for the males? Our computational simulations show that variation in female mating preferences increases variation in male mating success and accelerates the evolution of exaggerated ornaments. This finding, though, depends (among other things) on the magnitude of female variation.
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91. Santana, E.M., Machado, G., Kasumovic, M.M. 2020. Pre-maturation social experience affects female reproductive strategies and offspring quality in a highly polyandrous insect. Behavioral Ecology and Sociobiology, 74:135. (View)
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Is mating behavior of cricket females influenced by the calls of adult males heard during the pre-maturation period? We tested if the pre-maturation acoustic environment affects the number and attractiveness of accepted males, which may influence offspring quality. Pre-maturation acoustic environment does not affect the number of accepted males. However, offspring quality was affected by the pre-maturation acoustic environment and attractiveness of accepted males. Thus, pre- and post-maturation factors interact to determine offspring quality.
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2019
90. Rojas, A., Solano-Brenes, D., Muniz, D.G., Machado, G. 2019. Gone with the rain: negative effects of rainfall on male reproductive success in a nest-building arachnid. Behavioral Ecology, 30:1145–1156. (View)
90. Rojas, A., Solano-Brenes, D., Muniz, D.G., Machado, G. 2019. Gone with the rain: negative effects of rainfall on male reproductive success in a nest-building arachnid. Behavioral Ecology, 30:1145–1156. (View)
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The reproductive success of nest-building individuals is strongly influenced by nest quality. We investigated how rainfall affects nest integrity and consequently male mating success in a harvestman with exclusive paternal care. Rainfall destroyed 50% of the nests, and damage extension depended on precipitation volume and nest location. Males in high-integrity nests received more eggs than males in low-integrity nests. Thus, males should build nests in protected sites to preserve nest integrity and attract more females.
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89. Quesada-Hidalgo, R., Solano-Brenes, D., Requena, G.S., Machado, G. 2019. The good fathers: efficiency of male care and the protective role of foster parents in a Neotropical arachnid. Animal Behaviour, 150:147–155. (View)
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In species with exclusive paternal care, males may permanently abandon their clutches. Abandoned clutches can be adopted by conspecific males, because females usually prefer to mate with caring males. We studied a harvestman in which males build a mud-nest and care for the eggs alone. We found that males adopt unattended clutches and care for them as well as owner males. Egg adoption is a low-cost tactic that probably increases male reproductive success.
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2018
88. Solano-Brenes, D., García-Hernández, S., Machado, G. 2018. All the better to bite you with! Striking intrasexual differences in cheliceral size define two male morphs in an Amazonian arachnid. Biological Journal of the Linnean Society, 125:521–534. (View)
88. Solano-Brenes, D., García-Hernández, S., Machado, G. 2018. All the better to bite you with! Striking intrasexual differences in cheliceral size define two male morphs in an Amazonian arachnid. Biological Journal of the Linnean Society, 125:521–534. (View)
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When reproductive sites are scarce, large males may aggressively monopolize them and have exclusive access to females. Small males, however, may furtively invade reproductive sites and sneak copulations. Here we showed that territorial males of an Amazonian harvestman have enlarged chelicerae, which are used to bite and fend rivals off their territories. Sneaker males, in turn, have chelicerae similar to females. We suggest that male dimorphism coupled with alternative mating tactics is widespread in harvestmen.
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87. Eberhard, W.G., Rodríguez, R.L., Huber, B.A., Speck, B., Miller, H., Buzatto, B.A., Machado, G. 2018. Sexual selection and static allometry: the importance of function. The Quarterly Review of Biology, 93:207–250. (View)
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Structures under sexual selection often show positive allometry, which means they are disproportionately large in larger individuals. We propose that positive allometry should evolve more frequently in threat structures (including weapons) because they are used to avoid unwinnable fights with larger opponents. Courtship structures, though, convey information that is not consistently related to male size, thus positive allometry should evolve less frequently. In this study, we tested and confirmed these predictions using several animal species.
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86. Kury, A.B., Machado, G. 2018. Do the species with facies reclinobunoides make up a clade? — A new Lomanius (Opiliones, Podoctidae) from Vietnam and a discussion on its relationships. Zootaxa, 4441:151–170. (View)
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According to specialists, less than 60% of the harvestmen diversity has been described. Thus, there are many new species waiting to be named. Here we describe a new species from Vietnam. The most bizarre feature of this species is the ocular mound, which is large and strongly leaned back in males, but not in females. We don't know how males use this structure, but I bet it works as a weapon similar to deer antlers.
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85. Muniz, D.G., Baena, M.L., Macías-Ordóñez, R., Machado, G. 2018. Males, but not females, perform strategic mate searching movements between host plants in a leaf beetle with scramble competition polygyny. Ecology and Evolution, 8:5828–5836. (View)
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To search for mating partners is energetically costly and potentially dangerous. Thus, individuals should leave their locations only when mating opportunities are scarce and should go to close sites with better mating opportunities. We tested this hypothesis with a Mexican leaf beetle and found that males behave as expected by the theory, but females avoid sites with many males. In conclusion, while males are running after females, females are running away from males.
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84. García-Hernández, S., Machado, G. 2018. Convergent fighting behavior in two species of Neotropical harvestmen (Opiliones): insights on the evolution of maternal care and resource defense polygyny. Journal of Arachnology, 46:165–169. (View)
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Males of several harvestman species fight for the possession of oviposition sites. Here we describe the first case of male-male fight in cranaids. Fighting behavior is remarkably similar to that described for some gonyleptids. Morphological and behavioral similarities between these two families are evolutionary convergences. We suggest that increase in body and use of high vegetation were the key factors influencing the morphological and behavioral convergences related to their reproductive biology.
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83. Muniz, D.G, Machado, G. 2018. Mate sampling influences the intensity of sexual selection and the evolution of costly sexual ornaments. Journal of Theoretical Biology, 447:74–83. (View)
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During mate searching, females usually find few males and choose their mates based on limited information. Using computational simulations, we showed that this limitation has both short- and long term-implications. In the short-term, it attenuates the intensity of sexual selection on males because even unattractive individuals have some chance of being selected. In the long-term, it prevents the evolution of exaggerated male ornaments. Empirical data of several animal species support the predictions of our simulations.
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82. García-Hernández, S., Machado, G. 2018. Effectiveness of maternal egg attendance in an exclusively cave-dwelling harvestman (Arachnida: Opiliones). Journal of Zoology, 302:228–235. (View) Journal cover.
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Caves are a particular habitat because food is usually scarce and many species living there are predators. Thus, unprotected eggs represent a rich meal for many cave-dwellers. Here we showed that females of a cave harvestman are successful in defending their eggs against predators. They also lay very large eggs when compared to other maternal harvestmen. We suggest that large eggs produce large offspring, which are less vulnerable to intense predation inside the cave.
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2017
81. Muniz, D.G., Santos, E.S.A., Guimarães Jr., P.R., Nakagawa, S., Machado, G. 2017. A multinomial network method for the analysis of mate choice and assortative mating in spatially structured populations. Methods in Ecology and Evolution, 8:1321–1331. (View)
81. Muniz, D.G., Santos, E.S.A., Guimarães Jr., P.R., Nakagawa, S., Machado, G. 2017. A multinomial network method for the analysis of mate choice and assortative mating in spatially structured populations. Methods in Ecology and Evolution, 8:1321–1331. (View)
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Females cannot find all males in a population to select the best mating partner. Thus, it is important to consider the distance between individuals when studying mate choice. We developed a new statistical method that allows the inclusion of pairwise predictors, accommodating spatial distances between individuals in analyses of mate choice. Results obtained with simulated data show that including space in the analyses increases our ability to detect and estimate mate choice using observational data.
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80. Santos, E.S.A., Bueno, P.P., Gilbert, J.D.J., Machado, G. 2017. Macroecology of parental care in arthropods: higher mortality risk leads to higher benefits of offspring protection in tropical climates. Biological Reviews, 92:1688–1701. (View)
80. Santos, E.S.A., Bueno, P.P., Gilbert, J.D.J., Machado, G. 2017. Macroecology of parental care in arthropods: higher mortality risk leads to higher benefits of offspring protection in tropical climates. Biological Reviews, 92:1688–1701. (View)
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Intense egg mortality imposed by ants and fungi may have favored the evolution of parental in tropical arthropods. We tested this prediction using a meta-analysis approach, which combines information from many papers to reach broad conclusions. Unattended eggs of arthropods indeed suffer more intense predation in the tropics. We also showed that additional lines of egg defense (mucus coats or cocoons) increase offspring survival. Against powerful enemies, every defensive measure should be taken.
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79. Alissa, L.M., Muniz, D.G., Machado, G. 2017. Devoted fathers or selfish lovers? Conflict between mating effort and parental care in a harem-defending arachnid. Journal of Evolutionary Biology, 30:191–201. (View)
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When paternal care and female attraction are mutually exclusive tasks, theory predicts that "handsome" males should invest in female attraction, whereas "ugly" males should care for eggs. We tested this prediction with a harvestman species in which males defend harems, but may care for eggs if an egg-caring female of the harem dies. Our findings support the theoretical prediction. Thus, depending on their own attractiveness, males can be either devoted father or selfish lovers.
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2016
78. Consolmagno, R., Requena, G.S., Brasileiro, C.A., Machado, G. 2016. Costs and benefits of temporary egg desertion in a rocky shore frog with male-only care. Behavioral Ecology and Sociobiology, 70:785–795. (View)
78. Consolmagno, R., Requena, G.S., Brasileiro, C.A., Machado, G. 2016. Costs and benefits of temporary egg desertion in a rocky shore frog with male-only care. Behavioral Ecology and Sociobiology, 70:785–795. (View)
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In the Atlantic forest, there is a frog species that live and reproduce in rocky shores. If males find a nest-site protected from sun, they can care for eggs all day long. However, in sites exposed to sun, males need to leave the eggs unattended during daytime to avoid dehydration. Unprotected eggs are consumed by predators, including ants and snakes. Thus, the quality of the nest-site is crucial for males' reproductive success.
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77. Macedo-Rego, R.C., Costa-Schmidt, L.E., Santos, E.S.A., Machado, G. 2016. Negative effects of prolonged dietary restriction on male mating effort: nuptial gifts as honest indicators of long-term male condition. Scientific Reports, 6:21846. (View)
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When males of some spiders catch a prey, they need to decide if they eat it or use it to make a nuptial gift to females. This decision is probably influenced by males' hunger state. In fact, poorly-fed males always consume the prey, whereas well-fed males always make gifts. Even when poorly-fed males have access to a banquette, they rarely make nuptial gifts. Thus, starvation seems to impose a life-long trauma on males...
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76. Machado, G., Buzatto, B.A., García-Hernández, S., Macías-Ordóñez, R. 2016. Macroecology of sexual selection: a predictive conceptual framework for large-scale variation in reproductive traits. The American Naturalist, 188:S8–S27. (View)
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Here we explore how temperature and rainfall influence reproductive strategies in harvestmen. We show that species from warm/humid places have longer breeding seasons than species from cold/dry places. Moreover, when the breeding season is long, males attract females by defending territories and have weapons, including spines and horns. When the breeding season is short, males are weaponless males and simply chase females. Thus, aggressive male-male interactions for access to females are fiercer in hot/wet climates.
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75. Nazareth, T.M., Sudatti, D.B., Machado, G. 2016. Chemical defense as a condition-dependent trait in harvestmen. Journal of Chemical Ecology, 42:1047–1051. (View)
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Many harvestman species release stinky chemical secretions to repel predators. The composition of these secretions varies among species, but the production of complex chemical compounds are probably costly. To test this prediction, we depleted the glands of several individuals and divided them into two groups: well-fed and poorly-fed. After three weeks, the volume of secretion produced by well-fed harvestmen were higher than poorly-fed. This finding indicates that the production of chemical defenses is indeed costly.
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74. Santos, E.S.A., Machado, G. 2016. Sexual dichromatism in wing pigmentation of New World dragonflies follows Rensch's rule. Journal of Evolutionary Biology, 29:1447–1454. (View)
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In 1960, Rensch described a general pattern in nature: species with large body size tend to have more marked sexual dimorphism in size. Here we tested if the same pattern occurs for other type of sexual dimorphism: wing coloration of dragonflies. We quantified wing coloration of almost 100 species from New World and found that "Rensch rule" also applies to sexual coloration. Intense male-male competition for females probably is the best explanation to the rule.
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2015
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73. Muniz, D.G., Buzatto, B.A., P.R. Guimarães Jr, Machado, G. 2015. A sexual network approach to sperm competition in a species with alternative mating tactics. Behavioral Ecology, 26:121–129. (View) Included in the special volume "Sperm Competition and its Evolutionary Consequences" published in Behavioral Ecology (2020) to celebrate the 50th anniversary of Parker’s theory on sperm competition
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Imagine that individuals are linked to each other if they copulate. This is a sexual network, which provides information such as the risk of sexually transmitted diseases to spread. We described the sexual network of a harvestman species in which males defend harems. Females inside harems accept copulations with all invader males. Invaders may sneak copulation with females from several harems. Thus, many eggs laid females probably are not sired by the harem owners.
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72. Muniz, D.G., Machado, G. 2015. Experimental limitation of oviposition sites affects the mating system of an arachnid with resource defence polygyny. Animal Behaviour, 109:23–31. (View)
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In many species, the strongest males defend oviposition sites and monopolize the access to females. When oviposition sites are scarce, competition for females should be intense. We tested this prediction in a harvestman species that oviposit on some plant species. Competition for females didn't increase when we removed the preferred plants because females oviposited in other plants, which were then defended by males. We learned that behavioral flexibility is important when individuals face unfavorable situations.
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71. Nazareth, T.M., Machado, G. 2015. Egg production constrains chemical defenses in a Neotropical arachnid. PLoS One, 10:e0134908. (View)
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When resources are scarce, they need to be allocated wisely. Egg-production requires many resources that could be used in other tasks, such as the production of chemical defenses. We investigated the existence of this trade-off in a harvestman species with maternal care. The volume of chemical secretion suffers a 50% reduction during egg-production. After oviposition, females recover the "normal" volume of secretion and are well-protected again. Conclusion: there is no free lunch in nature!
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70. Requena, G.S., Machado, G. 2015. Effects of egg attendance on male mating success in a harvestman with exclusive paternal care. Behavioral Ecology, 26:926–935. (View)
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In a previous study, we showed that males of a harvestman species protect their eggs against predators. However, males starve during parental care and need to abandon their clutches. Thus, females should select males in the beginning of the caring period because they still have enough energy to care for additional eggs. We tested this prediction and found support for it. We suggest that females select partners based on the caring quality of potential partners.
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2014
69. Requena, G.S., Machado, G. 2014. Lack of costs associated with nest-related behaviors in an arachnid with exclusive paternal care. Oikos, 124:372–380. (View)
69. Requena, G.S., Machado, G. 2014. Lack of costs associated with nest-related behaviors in an arachnid with exclusive paternal care. Oikos, 124:372–380. (View)
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Although males of many harvestman species care for eggs, only in a few species they also build mud-nests used by females as exclusive oviposition site. We evaluated if nest building and maintenance imposes costs to males. We found that nesting-males do not lose weight during the breeding season, suggesting that they can feed inside or around their nests. Surprisingly, nesting-males have higher survival than non-nesting males. Thus, nest building offers great benefits at low costs.
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68. Buzatto, B.A., Machado, G. 2014. Male dimorphism and alternative reproductive tactics in harvestmen (Arachnida: Opiliones). Behavioural Processes, 109:2–13. (View)
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Male dimorphism occurs when we find two male morphs in the same species. Major males are large and heavily armed. They fight for the possession of territories where females lay eggs. Minor males are small, unarmed, and female-like. They don't fight, but rather invades territories to sneak copulations. Here we revise all cases of male dimorphism in harvestmen and indicate some gaps in our knowledge as well as possible directions to future studies.
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67. Buzatto, B.A., Tomkins, J.L., Simmons, L.W., Machado, G. 2014. Correlated evolution of sexual dimorphism and male dimorphism in a clade of Neotropical harvestmen. Evolution, 68:1671–1686. (View)
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In many harvestman species we can find two male morphs in nature: one large and heavily armed morph, and another small, unarmed, and female-like morph. Theory predicts that this so-called male dimorphism should evolve only in species showing marked sexual dimorphism. We tested this prediction using a group of neotropical harvestmen with incredible morphological diversity. Our results support this prediction, showing that sexual dimorphism always precedes the evolution of male dimorphism.
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66. Chelini, M.C., Machado, G. 2014. Multiple lines of egg defense in a Neotropical arachnid with temporary brood desertion. Ethology, 120:1147–1154. (View)
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Females of the gladiator harvestman care for eggs. During the long caring period, they need to leave their clutches temporarily unattended to feed and take shelter. In a previous study, we showed that eggs are severely attacked during maternal absence. However, eggs are surrounded by a thick mucus coat that may hamper egg consumption by some predators. Here we experimentally showed that the mucus coat indeed confers protection to eggs against a common, small-sized predator.
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65. Requena, G.S., Machado, G. 2014. Mating behavior of a Neotropical arachnid with exclusive paternal care. Acta Ethologica, 17:23–30. (View)
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In some species with exclusive paternal care, females may compete for the assess to caring males. Males, in turn, may become choosy and select the best females. We call it "sex role reversal". Here we investigated if a harvestman with exclusive paternal care exhibit sex role reversal. Although we never observed females fighting for males, we recorded several males rejecting females before and after copulation. This finding suggests that harvestman daddies are hard to please.
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2013
64. Caetano, D.S., Machado, G. 2013. The ecological tale of Gonyleptidae (Arachnida, Opiliones) evolution: phylogeny of a Neotropical lineage of armoured harvestmen using ecological, behavioural and chemical characters. Cladistics, 29:589–609. (View) Journal cover.
64. Caetano, D.S., Machado, G. 2013. The ecological tale of Gonyleptidae (Arachnida, Opiliones) evolution: phylogeny of a Neotropical lineage of armoured harvestmen using ecological, behavioural and chemical characters. Cladistics, 29:589–609. (View) Journal cover.
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How can scientist say that two species are related to each other? They can use similarities in different types of traits, including morphology, DNA sequences, and more rarely behavior. Here, we inferred the relationship among harvestman species belonging to a highly diverse Neotropical group. We used many behavioral and chemical traits, and showed that both are useful to recognize subgroups. Thus, the general prejudice against behavioral traits in the classification of animals is unjustified.
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63. Rocha, D.F.O., Wouters, F.C., Machado, G., Marsaioli, A.J. 2013. First biosynthetic pathway of 1-hepten-3-one in Iporangaia pustulosa (Opiliones). Scientific Reports, 3:3156. (View)
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Once more, I collaborated with a group of chemists to understand how harvestmen produce ketones, a particular type of defensive secretion. As in our previous study, we found that the building blocks are simple molecules that can be obtained in almost every food. Contrary to our previous studies, though, the enzymes required to put the blocks together are not a mystery and have already been reported in other arthropod species that release ketones as defense.
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62. Rocha, D.F.O., Wouters, F.C., Zampieri, D., Brocksom, T., Machado, G, Marsaioli, A.J. 2013. Harvestman phenols and benzoquinones: characterisation and biosynthetic pathway. Molecules, 18:11429–11451. (View)
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In this study, conducted in collaborated with a group of chemists, we investigated how the defensive secretions released by harvestmen are produced. Our findings show that the biosynthesis of a widespread chemical compound of Neotropical harvestmen involves simple building blocks, easily acquired in the diet. However, the fusion of these blocks requires enzymes that are unknown to occur in arthropods. Thus, we suspect that harvestmen receive some help from bacteria, which have the necessary enzymes
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61. Wouters, F.C., Rocha, D.F.O., Gonçalves, C.C.S., Machado, G., Marsaioli, A.J. 2013. Additional vinyl ketones and their pyranyl ketones in gonyleptid harvestmen (Arachnida: Opiliones) suggest these metabolites are widespread in this family. Journal of Natural Products, 76:1559–1564. (View)
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Here, my chemist collaborators and I report the occurrence of ketones in the chemical secretion of four harvestman species. Considering that these species are closely-related to each other, and are also related to the species in which we first recorded the presence of ketones, we propose that the presence of ketones may be a useful character in taxonomic studies of the family Gonyleptidae. To test this hypothesis, we need to sample more species.
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2012
60. Chelini, M.C., Machado, G. 2012. Costs and benefits of temporary brood desertion in a Neotropical harvestman (Arachnida: Opiliones). Behavioral Ecology and Sociobiology, 66:1619–1627. (View)
60. Chelini, M.C., Machado, G. 2012. Costs and benefits of temporary brood desertion in a Neotropical harvestman (Arachnida: Opiliones). Behavioral Ecology and Sociobiology, 66:1619–1627. (View)
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Females of the gladiator harvestman care for eggs laid under leaves. Contrary to other maternal harvestmen, they keep adding eggs to their clutches during the caring period. Because the caring period is long, females need to abandon their clutches to feed or to shelter when the climate is dry. Although temporary desertion is important to caring females, their eggs are consumed by predators when they are away. This is the real "mother's dilemma"!
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59. Costa-Schmidt, L.E., Machado, G. 2012. Reproductive interference between two sibling species of gift-giving spiders. Animal Behaviour, 84:1201–1211. (View)
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Two closely-related spider species live together. In both, males offer a prey wrapped in silk to the females before copulation. Because the two species are very similar, do males misrecognize females of their species? Yes, they do, and the effects are dramatic! If a male offers a prey to a female of other species that is larger than him, she can attack and consume him. Thus, males need to be careful when looking for mates.
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58. Munguía-Steyer, R., Buzatto, B.A., Machado, G. 2012. Male dimorphism of a neotropical arachnid: harem size, sneaker opportunities, and gonadal investment. Behavioral Ecology, 23:827–835. (View)
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Sperm competition is a form of male-male struggle that occurs inside females in species with internal fertilization (including us!). Theory predicts that when sperm competition is strong, males should invest in more sperm. We tested this prediction in 10 populations of a harvestman species, but found no support for it. However, we found that males with large harems experience more sperm competition because it's harder to protect all females from the invasion of other males.
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57. Requena, G.S., Buzatto, B.A., Martins, E.G., Machado, G. 2012. Paternal care decreases foraging activity and body condition, but does not impose survival costs to caring males in a neotropical arachnid. PLoS One, 7:e46701. (View)
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Andy Warhol said: "Everybody will be world famous for 15 minutes". We experienced our 15 minutes with this paper. We showed that males of harvestman species starve while caring for the eggs. However, caring males are preferred as mating partners by the females, accumulating more than 100 eggs in their clutches. But what called the media attention was: caring males live longer than non-caring males. Thus, to be father is a very good deal!
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56. Werneck, R.M., Caetano, D.S., Machado, G. 2012. Maternal care in the Neotropical harvestman Liogonyleptoides tetracanthus (Opiliones: Gonyleptidae). Journal of Arachnology, 40:135–137. (View)
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During a fieldtrip to Espírito Santo (Brazil), we collected individuals of a large harvestman species to study their behavior in our lab. Luckily, females laid eggs under the rocks we placed in their cages. We found they care for the eggs, repelling individuals of the same species that cannibalize unprotected eggs. We think maternal care will be a useful character to recognize related species in future studies with harvestman of the family Gonyleptidae.
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2011
55. Buzatto, B.A., Requena, G.S., Lourenço, R. S., Munguía-Steyer, R., Machado, G. 2011. Conditional male dimorphism and alternative reproductive tactics in a Neotropical arachnid (Opiliones). Evolutionary Ecology, 25:331–349. (View)
55. Buzatto, B.A., Requena, G.S., Lourenço, R. S., Munguía-Steyer, R., Machado, G. 2011. Conditional male dimorphism and alternative reproductive tactics in a Neotropical arachnid (Opiliones). Evolutionary Ecology, 25:331–349. (View)
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While we’re studying maternal care in a harvestman species, we discovered interesting things about males' behavior. In a previous paper, we described male-male fights for the possession of territories where females lay eggs and stay caring for the eggs. Here we found that some males in the population are small, don't have the elongation of the second legs used as weapons, and sneak copulations with egg-caring females inside the harems.
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54. Rocha, D.F.O., Hamilton, K., Gonçalves, C.C.S., Machado, G., Marsaioli, A.J. 2011. 6-Alkyl-3,4-dihydro-2: Chemical secretion compounds in Neotropical harvestmen. Journal of Natural Products, 74:658–663. (View)
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This work is another collaboration with the lab of Dr. Anita Marsaioli at State University of Campinas. We described the chemical composition of the defensive secretion of five harvestman species. In two species, we found a new natural product formed by the fusion of two ketones, a compound of the nail polish removers. The origin of the molecule is a mystery because it requires incredibly high temperature and pressure to be synthesized in the lab.
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53. Villarreal-Manzanilla, O., Machado, G. 2011. First record of paternal care in the family Stygnidae (Opiliones: Laniatores). Journal of Arachnology, 39:500–502. (View)
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During a fieldtrip in Venezuela, my colleague "Camomila" found males of two harvestman species caring for eggs. Here invited me to write this note, which is the first record of paternal care in a harvestman family that occurs mainly in the Amazon region. As other harvestman species with paternal care, males care for eggs laid by multiple females. Based on studies we conducted with other harvestman species, we suspect that females prefer caring males.
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52. Zatz, C., Werneck, R.M., Macías-Ordóñez, R., Machado, G. 2011. Alternative mating tactics in dimorphic males of the harvestman Longiperna concolor (Arachnida: Opiliones). Behavioral Ecology and Sociobiology, 65:995–1005. (View)
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Males of some harvestman species have the fourth pair of legs ten times longer than females. The reason of this sexual dimorphism was unknown. We found that males use their elongated legs to hit each other in fights for the possession of territories on rocks and trunks. Females visit these territories to lay eggs and stay there. Some males have a female-like appearance, do not fight, but invade territories to copulate furtively with some females.
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2010
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51. Nazareth, T.M., Machado, G. 2010. Mating system and exclusive postzygotic paternal care in a Neotropical harvestman (Arachnida: Opiliones). Animal Behaviour, 79:547–554. (View) Editor's choice.
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A theory published in 2001 proposes that males that effectively protect the offspring are the best mating partners. Two predictions of the theory are: females should select caring males and non-caring males should adopt unrelated eggs to increase their attractiveness. We tested these predictions using a harvestman with paternal care. We found support for both predictions, suggesting that sexual selection favors paternal care. This paper was the "editor's choice" of the volume published in 2010.
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50. Pomini, A.M., Machado, G., Pinto-da-Rocha, R., Macías-Ordóñez, R., Marsaioli, A.J. 2010. Lines of defense in the harvestman Hoplobunus mexicanus(Arachnida: Opiliones): aposematism, stridulation, thanatosis, and irritant chemicals. Biochemical Systematics and Ecology, 38:300–308. (View)
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I really love Mexico. This work has been done with a Mexican harvestman species that occurs in a forest fragment close the house of my great friend Rogelio. We described the lines of defense of this harvestman species. Upon initial disturbance, individuals usually run or feign death. If we grab them on hands, they may release a strong chemical secretion. In some cases, they can also stridulate, producing a low, but hearable buzzzzz!
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49. Requena, G.S., Schwertner, C.F., Machado, G., Nazareth, T.M. 2010. First cases of exclusive paternal care in stink bugs (Hemiptera: Pentatomidae). Zoologia, 27:1018–1021. (View)
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Once, when we're doing fieldwork at Intervales State Park, we found a male stinkbug caring for eggs. In the same trip we found a male of another stinkbug species caring for eggs. We enjoyed this opportunity to make some basic behavioral observations. After that, we spent three years searching for caring more males, but we never found anything. Thus, we decided to publish a note, which is the first record of paternal care in stinkbugs.
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2009
48. Buzatto, B.A., Machado, G. 2009. Amphisexual care in Acutisoma proximum (Arachnida, Opiliones), a neotropical harvestman with exclusive maternal care. Insectes Sociaux, 56:106–108. (View)
48. Buzatto, B.A., Machado, G. 2009. Amphisexual care in Acutisoma proximum (Arachnida, Opiliones), a neotropical harvestman with exclusive maternal care. Insectes Sociaux, 56:106–108. (View)
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In some species, when the caring individual deserts or dies, the other parent, which usually is not involved in parental activities, may care for the unattended offspring. We showed that males of a harvestman species that defend territories used by females as oviposition site may care for eggs if an egg-tending female is experimentally removed from the harem. Not all territorial males do that, but some care for eggs for as long as one week.
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47. Buzatto, B.A., Requena, G.S., Machado, G. 2009. Chemical communication in the gregarious psocid Cerastipsocus sivorii (Psocoptera: Psocidae). Journal of Insect Behavior, 22:388–398. (View)
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In a paper we published in 2007, we described that nymphs of an urban bark lice species form large aggregations on tree trunks. Here we showed that chemical cues of a crushed nymph induce a general dispersion of the aggregations, possibly because the smell indicates that someone has been attacked nearby. Moreover, nymphs recognize chemical cues of individuals of the same species, which may help stray individuals to find each other after dispersion.
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46. Kury, A.B., Machado, G. 2009. Notes on Santobius from Vanuatu and Fiji and the status of the eastern Melanesian Ibalonius (Arachnida, Opiliones, Podoctidae). Zoological Studies, 48:524–538. (View)
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Many years ago, my crazy friend Adrik showed me some male harvestmen from the Salomon islands carrying eggs on their legs. It was a new species, and we were unable to even say its genus. Thus, we decided to construct a phylogeny for the entire family. The phylogeny is still under construction, and this paper is only a tiny piece of our work on the systematics of the family. To be continued...
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45. Machado, G., Requena, G.S., Buzatto, B.A. 2009. Comportamento reprodutivo de opiliões (Arachnida): sistemas de acasalamento e cuidado parental. Oecologia Brasiliensis, 13:58–79. (View)
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In the two years after the publication of the book The Biology of Biology, several papers on mating system and parental care in harvestmen have been published. In this review, we update the chapter on reproduction, presenting new data for several tropical species. We wrote this paper for an invited volume of the journal Oecologia Brasiliensis devoted to the subject "Behavioral Ecology in Brazil". This is why the paper has been written in Portuguese.
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44. Nazareth, T.M., Machado, G. 2009. Reproductive behavior of Chavesincola inexpectabilis (Opiliones, Gonyleptidae) with description of a new and independently evolved case of paternal care in harvestmen. Journal of Arachnology, 37:127–134. (View)
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We describe a new case of paternal care in a harvestman species from the Atlantic forest. Males care for eggs under small fallen trunks. As in other species, males receive eggs from several females. Because females don't care for the eggs and are free to forage, they are able to lay eggs at each other day. From the males' perspective it is good because there is always a female willing to mate and lay eggs.
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43. Requena, G.S., Buzatto, B.A., Munguía-Steyer, R., Machado, G. 2009. Efficiency of uniparental male and female care against egg predators in two closely related syntopic harvestmen. Animal Behaviour, 78:1169–1176. (View)
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Are males as good as females in protecting eggs against predators? We answered this question using two harvestman species that live together, but differ in the sex of the caring parent. We showed that the protection provided by males and females is similar. However, when parents are absent, egg survival was higher in the paternal species. We found that it occurs because eggs of the paternal species have a mucus coat female that hampers consumption.
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42. Uehara-Prado, M., Fernandes, J.O., Bello, A., Machado, G., Santos, A.J., Vaz-de-Mello, F., Freitas, A.V.L. 2009. Selecting terrestrial arthropods as indicators of small-scale disturbance: a first approach in the Brazilian Atlantic forest. Biological Conservation, 142:1220–1228. (View)
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Human development is unfortunately coupled with disturbance of natural environments. Given that a comprehensive sampling of all animal groups is impossible, ecologists use bioindicators, which are organisms that work as ‘shortcuts’ to assess the ecological integrity of the whole community. Here, we assessed the effects of human disturbance on terrestrial arthropods in the Atlantic Forest. We showed that spiders, beetles, and fruit-feeding butterflies are useful bioindicators of human disturbance.
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41. Willemart, R.H., Osses, F., Chelini, M.C., Macías-Ordóñez, R., Machado, G. 2009. Sexually dimorphic legs in a neotropical harvestman (Arachnida, Opiliones): ornament or weapon? Behavioural Processes, 80:51–59. (View)
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Males of many harvestman species have spines on their hind legs. Although taxonomists use these spines to recognize species, their biological role was unknown. We showed for the first time that males of the gladiator harvestman use leg spines in combats. With a sudden upward movement, one male brings one fourth leg close to the body, pinching the fourth leg of the opponent between huge leg species. Thus, we can say that spines are weapons.
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2008
40. Bonato, V., Martins, E.G., Machado, G., Da-Silva, C.Q., Reis, S.F. 2008. Ecology of the armadillos Cabassous unicinctus and Euphractus sexcinctus (Cingulata: Dasypodidae) in a Brazilian Cerrado. Journal of Mammalogy, 89:168–174. (View)
40. Bonato, V., Martins, E.G., Machado, G., Da-Silva, C.Q., Reis, S.F. 2008. Ecology of the armadillos Cabassous unicinctus and Euphractus sexcinctus (Cingulata: Dasypodidae) in a Brazilian Cerrado. Journal of Mammalogy, 89:168–174. (View)
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When I was doing my PhD, I helped a friend to describe the ecology of two species of armadillos from the Brazilian savannah: the naked-tailed armadillo and the 6-banded armadillo. Whereas the first species is mostly diurnal, the second is mostly nocturnal. The two species occur in both open and forested areas, but the naked-tailed armadillo prefer the later. During the winter, when insects are scarce, armadillos need to move more to find food.
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39. Buzatto, B.A., Machado, G. 2008. Resource defense polygyny shifts to female defense polygyny over the course of the reproductive season of a Neotropical harvestman. Behavioral Ecology and Sociobiology, 63:85–94. (View)
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Don't think that only sultans and lions have harems! Here we showed that males of a harvestman from the Atlantic forest fight each other for the possession of vegetation patches close to river margins. These patches are visited by females, which copulate with the territory owner and lay their eggs under the leaves. Because females stay caring for the eggs, a successful male can accumulate as much as 10 females inside his harem.
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38. Machado, G., Pomini, A.M. 2008. Chemical and behavioral defenses of the neotropical harvestman Camarana flavipalpi (Arachnida: Opiliones). Biochemical Systematics and Ecology, 36:369–376. (View)
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Defensive strategies in harvestmen show great variation among species. Some species promptly release chemical secretions upon disturbance, whereas other species run away or feign death. We studied the defensive repertoire of a small ground harvestman and showed that individuals are reluctant in releasing chemical secretions. Upon manipulation, the most frequent strategy is to feign death. However, when they really get angry, they release a nasty secretion to escape.
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37. Osses, F., Martins, E.G., Machado, G. 2008. Oviposition site selection by the bromeliad-dweller harvestman Bourguyia hamata (Arachnida: Opiliones). Journal of Ethology, 26:233–241. (View)
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During my PhD, I showed that females of a harvestman species oviposit exclusively inside a bromeliad that forms a leaf tube. My first master's student investigated if females also select individuals of this bromeliad as oviposition site. We found that females prefer larger bromeliads, which accumulate more water in the leaf tube. Females also prefer bromeliads with small amounts of debris inside the leaf tube. Thus, when the subject is oviposition, females are really picky!
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36. Osses, F., Nazareth, T.M., Machado, G. 2008. Activity pattern of the Neotropical harvestman Neosadocus maximus (Opiliones, Gonyleptidae): sexual and temporal variations. Journal of Arachnology, 36:518–526. (View)
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The gladiator harvestman is very common in the Atlantic forest and is a good model for behavioral studies. Here we provide a basic description of the behavioral repertoire of this species as a starting point for future experimental work. Individuals are more active at night and during the summer, which corresponds to the breeding season. Moreover, males and females showed marked differences in the frequency and number of behaviors exhibited in captivity.
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2007
35. Araújo, M.S., Bolnick, D.I., Machado, G., Giaretta, A.A., Reis, S.F. 2007. Using delta 13C stable isotopes to quantify individual-level diet variation. Oecologia, 152:643–654. (View)
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"You are what you eat". This is true and we can investigate the diet of many animals analyzing the chemical composition of their bodies. We developed a new procedure to transform chemical composition into an index of diet specialization. We also applied this procedure to four frog species for which data on diet specialization were available. In general, our procedure seems to work well, providing a tool for quantifying diet specialization in natural populations.
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34. Araújo, M.S., Reis, S.F., Giaretta, A.A., Machado, G., Bolnick, D.I. 2007. Intrapopulation diet variation in four frogs (Leptodactylidae) of the Brazilian savannah. Copeia, 2007:855–865. (View)
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This work is part of the PhD dissertation I co-advised. We investigated age and sex-related diet variation in four frog species from Brazilian savannah. Although we found no age or sex-related differences in the prey types consumed by the four species, we did found evidence of individual-level diet variation in all studied species. It means that each individual specializes its diet in particular prey types, which may be a way of attenuating competition for food.
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33. Buzatto, B.A., Requena, G.S., Martins, E.G., Machado, G. 2007. Effects of maternal care on the lifetime reproductive success of females in a neotropical harvestman. Journal of Animal Ecology, 76:937–945. (View)
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Females of many species face a dilemma. If they care for the eggs, they don't feed and don't produce more eggs. However, if they abandon their eggs to feed, predators may kill the unattended offspring. Here we experimentally quantified the costs and benefits of maternal care in a harvestman species and showed that egg attendance pays-off. Although non-caring females produce 18% more eggs than caring females, unattended eggs experience predation of nearly 90%.
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32. Guimarães Jr., P.R. , Machado, G., De Aguiar, M.A.M., Jordano, P., Bascompte, J., Pinheiro, A., Reis, S.F. 2007. Build-up mechanisms determining the topology of mutualistic networks. Journal of Theoretical Biology, 249:181–189. (View)
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Plant-animal mutualisms can be understood as a network of interactions. In nature, the number of interactions per species in mutualistic networks shows a clear pattern: only a few species interact with many partners. Using simulations, we showed that this pattern is expected to occur when the number of species from one set (plants or animals) grows faster and reaches a higher number of species than the other set. Simple explanation for a general pattern.
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31. Machado, G. 2007. Maternal or paternal egg guarding? Revisiting parental care in triaenonychid harvestmen (Opiliones). Journal of Arachnology, 35:202–204. (View)
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In 1954, a researcher published a work on the taxonomy and biology of New Zealand harvestmen. In this work, he said that some species show maternal care, but provided no photo. In 1999, he published a book on New Zealand arachnids containing a photo of an egg-caring harvestman. Based on this photo, there is no doubt that egg-caring is performed by males and not females. In this note, I correct this mistake.
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30. Moya, J., Mancini, K.C., Machado, G., Dolder, H. 2007. Sperm morphology of the neotropical harvestman Iporangaia pustulosa (Arachnida: Opiliones): Comparative morphology and functional aspects. Arthropod Structure & Development, 36:53–62. (View)
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My office during the post-doc was close to the Department of Cell Biology, where I met a friend from the undergraduate course. She was working with sperm morphology and decided to describe the fine sperm morphology of a harvestman species with paternal care. We found that sperm is aflagellate and immotile. Given that eggs are fertilized on the tip of the female's ovipositor just prior oviposition, there is no advantage favoring sperm mobility in harvestmen.
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29. Requena, G.S., Buzatto, B.A., Machado, G. 2007. Habitat use, phenology, and gregariousness of the neotropical psocopteran Cerastipsocus sivorii (Psocoptera: Psocidae). Sociobiology, 49:197–214. (View)
29. Requena, G.S., Buzatto, B.A., Machado, G. 2007. Habitat use, phenology, and gregariousness of the neotropical psocopteran Cerastipsocus sivorii (Psocoptera: Psocidae). Sociobiology, 49:197–214. (View)
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Tree trunks at State University of Campinas are commonly used by a species of bark lice that forms large aggregations composed mainly of nymphs. Considering that nymphs are flightless and will spend their lives on the same tree, females should be very picky when selecting oviposition sites. Contrary to this expectation, nymphs occurred randomly in different tree species. Apparently, nymphs find abundant food and shelter in all tree species in the study site.
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2006
28. Almeida-Neto, M., Machado, G., Pinto-da-Rocha, R., Giaretta, A.A. 2006. Harvestman species distribution along three neotropical elevational gradients: an alternative rescue effect to explain Rapoport’s rule. Journal of Biogeography, 33:361–375. (View)
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Species distribution along environmental gradients has long attracted the attention of ecologists. We investigated how the number of harvestman species varies along altitudinal gradients in the Atlantic forest. Species number clearly decreases with altitude, a pattern predicted by the "Rapoport rule". Only a few species living in the lower parts of the mountains are able to tolerate the climatic conditions of the peaks and colonize the higher parts of the mountains.
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27. Dias, S.C., Machado, G. 2006. Microhabitat use by the whip spider Heterophrynus longicornis (Amblypygi, Phrynidae) in central Amazon. Journal of Arachnology, 34:540–544.(View)
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The presence of huge whip-spiders in many tree trunks in the Amazon forest always called my attention. Here we investigated if individuals select the trees they use as habitat. Our findings show that individuals are indeed very picky. They select large tree trunks bearing buttresses and burrows at the base where individuals hide during daytime. Thus, human disturbance promoted by logging may have negative effects on whip-spiders in the Amazon forest.
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26. Machado, G., Warfel, J. 2006. First case of maternal care in the family Cranaidae (Opiliones, Laniatores). Journal of Arachnology, 34:269–272. (View)
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My friend Joe Warfel is an excellent photographer who loves arachnids. During a fieldtrip to Trinidad, he found females of a harvestman species caring for eggs in a damp pocket of a roadside bank. Based on the photos, we identified the harvestman species and found that it was the first record of maternal care in the family Cranaidae. Species of this family show several morphological and behavioral similarities with some species of the family Gonyleptidae.
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2005
25. Machado, G., Carrera, P.C., Pomini, A.M., Marsaioli, A.J. 2005. Chemical defense in harvestmen (Arachnida, Opiliones): do benzoquinone secretions deter invertebrate and vertebrate predators? Journal of Chemical Ecology, 31:2519–2539. (View)
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Many tropical harvestmen release secretions with strong smell upon disturbance. Although the chemical composition of these secretions has already been investigated, their role as a repellent of potential predators was poorly understood. We experimentally showed that the secretion of a harvestman species is highly effective in repelling ants, spiders, and frogs, but not opossums. The secretion also works as a chemical shield against ants, preventing their approach for more than 10 minutes.
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2004
24. Pereira, W., Elpino-Campos, A., Del-Claro, K., Machado, G. 2004. Behavioral repertory of the Neotropical harvestman Ilhaia cuspidata (Opiliones, Gonyleptidae). Journal of Arachnology, 32:22–30. (View)
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Most behavioral studies of tropical harvestmen focus on species with parental care. Here we describe the behavior of a widespread harvestman that occurs in the Brazilian savannah and also in urban areas of central, southern, and southeastern Brazil. In this species, females lay isolated eggs, cover them with debris, and then abandon the offspring. Like other harvestman species, individuals are nocturnal and form small diurnal aggregations under logs and rocks.
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23. Martins, E.G., Bonato, V., Machado, G., Rocha, L.S., Pinto-da-Rocha, R. 2004. Description and ecology of a new species of sun spider (Arachnida: Solifugae) from the Brazilian Cerrado. Journal of Natural History, 38:2361–2375. (View)
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During fieldwork in the Brazilian savannah, we found a small arachnid running fast on the sand. For our surprise, it was a new species of sun-spider, a poorly-studied arachnid group. We named this species Mummucia coaraciandu, which means sun-spider in the language of native Brazilian Indians. We also studied the ecology of this species and showed that individuals are diurnal, and the peak of their activity occurs during the cold-dry season.
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22. Machado, G., Requena, G.S., Buzatto, B.A., Osses, F., Rossetto, L.M. 2004. Five new cases of paternal care in harvestmen (Arachnida: Opiliones): implications for the evolution of male guarding in the Neotropical family Gonyleptidae. Sociobiology, 44:577–598. (View)
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Although modest, this paper is a turning point in my career because I decided to focus my studies on the evolution of paternal care. As a first step for further studies, we describe paternal care in five harvestman species from the Atlantic forest. Males of these five species care for clutches composed of eggs laid by several females, showing that egg care and female attraction are not mutually exclusive activities in harvestmen.
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21. Christianini, A.V., Machado, G. 2004. Induced biotic responses to herbivory and associated cues in the Amazonian ant-plant Maieta poeppigii. Entomologia Experimentalis et Applicata, 112:81–88. (View)
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During a field course in the Amazon forest, we evaluated if the ants inhabiting small shelters in the leaves of a shrub called Maieta protect the host plant against herbivores. Using field experiments, we showed that ants attack insects that land on the leaves. Moreover, we showed that ants are promptly attracted to leaves that were experimentally cut. This finding suggests that the host plant communicates leaf damages to their "bodyguards".
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2003
20. Melo, A.S., Pereira, R.A.S., Santos, A.J., Shepherd, G.J., Machado, G., Medeiros, H.F., Sawaya, R.J. 2003. Comparing species richness among assemblages using sample units: why not use extrapolation methods to standardize different sample sizes? Oikos, 101:398–410. (View)
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I'm not a community ecologist, but many friends in my graduate program were. This paper is fruit of a collaboration with some of these friends. We evaluated the reliability of "extrapolation techniques", which are methods to estimate the number of species expected to occur in a place if the sampling effort was higher. We found that some extrapolation techniques provide reliable estimations for different groups, including both plants and animals.
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19. Hara, M.R., Gnaspini, P., Machado, G. 2003. Male egg guarding behavior in the Neotropical harvestman Ampheres leucopheus (Mello-Leitão, 1922) (Opiliones, Gonyleptidae). Journal of Arachnology, 31:441–444. (View)
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Until this paper, only three cases of exclusive paternal care have been reported in harvestmen, one in Panama, one in Nepal, and one in the Philippines. Here we describe a fourth case of paternal care in harvestmen and the first for the rich Atlantic forest fauna. Males of Ampheres leucopheus care for eggs laid on the undersurface of leaves. More than one female adds eggs to the clutch under male protection, and the eggs are surrounded by a thick mucus coat released by the females.
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2002
18. Machado, G., Bonato, V., Oliveira, P.S. 2002. Alarm communication: a new function for the scent-gland secretion in harvestmen (Arachnida: Opiliones). Naturwissenschaften, 89:357–360. (View)
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Many harvestman species release chemical secretions when disturbed by potential predators. Some of them form large diurnal aggregations on boulders and cave walls. We tested by the first time if the chemical secretion released by one individual works as an alarm signal for other individuals of the aggregation. In a field experiment, we showed that the chemical secretion elicits a collective dispersion of the aggregation. Moreover, the larger the aggregation the faster was the dispersion.
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17. Machado, G. 2002. Maternal care, defensive behavior, and sociality in Neotropical Goniosoma harvestmen (Arachnida, Opiliones). Insectes Sociaux, 49:388–393. (View)
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Among Neotropical harvestmen, the subfamily Goniosomatinae concentrates most of the studies on behavior. The group includes nearly 40 species that occur almost exclusively in the Atlantic Forest. In this review, I show that these species share many behavioral traits, including: females care for eggs and early hatched nymphs, individuals form diurnal aggregations mainly inside caves, foraging occurs on the vegetation at night, and both males and females release powerful chemical defenses against predators.
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16. Machado, G., Oliveira, P.S. 2002. Maternal care in the Neotropical harvestman Bourguyia albiornata (Arachnida: Opiliones): oviposition site selection and egg protection. Behaviour, 139:1509–1524. (View)
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Females of a harvestman species lay their eggs exclusively inside the leaf-tube formed by a bromeliad. This leaf-tube accumulates water and creates a humid environment that probably favors egg development. Moreover, females care for their eggs, protecting them from ants, which are the most common egg predator on the vegetation in the study site. The breeding season stops during the flowering period of the bromeliad, probably because in inflorescence stalk occupies the leaf-tube.
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15. Machado, G., Giaretta, A.A., Facure, K.G. 2002. Reproductive cycle of a population of the guaru, Phallocerus caudimaculatus (Poeciliidae), in Southeastern Brazil. Studies on Neotropical Fauna and Environment, 37:15–18. (View)
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We provide the first report on the reproductive cycle of a live-bearing guppy that inhabits streams in the Atlantic forest. Larger females have more embryos, a widespread pattern among cold-blood vertebrates. The peak of the reproductive activity occurs during the warm-wet season, when greater food supply may provide optimal conditions for the growth of juveniles. This was the first paper I wrote in my career, and it has been rejected five times before acceptance.
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14. Machado, G., Chagas Jr, A. 2002. Three new cases of maternal care in Neotropical centipedes (Chilopoda: Scolopendromorpha). Entomological News, 113:37–40. (View)
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Well, what should I say? Three more cases of maternal care in centipedes... I know that this type of information may seem useless for many people. However, comprehensive comparative studies rely on basic data on size, diet, fecundity, etc. This note is my small contribution to future studies on the evolution of life-history traits in centipedes ― a very interesting, but highly neglected group of arthropods.
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13. Pinto-da-Rocha, R., Machado, G., Weygoldt, P. 2002. Two new species of Charinus Simon, 1892 from Brazil with biological notes (Arachnida; Amblypygi; Charinidae). Journal of Natural History, 36:107–118. (View)
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During fieldwork on an island in southeastern Brazil, we found a new species of whip-spider, a poorly-studied arachnid group. We described this new species and named it Charinus asturius in reference to the ship "Prince of Asturia", which sank near the place we found the species. Given that individuals are found in only a small area of a single mountain of the island, the new species is born to scientists as already threatened of extinction.
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2001
12. Elpino-Campos, A., Pereira, W., Del-Claro, K., Machado, G. 2001. Behavioural repertory and notes on natural history of the Neotropical harvestmanDiscocyrtus oliverioi (Opiliones: Gonyleptidae). Bulletin of the British Arachnological Society, 12:144–150. (View)
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Here we describe the general behavior of a harvestman species that inhabits the Brazilian savannah. Individuals spend the daylight hours resting under shelters, sometimes forming aggregations. At night, they leave their shelters to forage. Individuals eat both live and dead arthropods. Females care for the eggs and attach debris on the eggs, probably to camouflage them. Early hatched nymphs remain close to the mother for some days, and then they disperse.
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11. Machado, G., Freitas, A.V.L. 2001. Larval defence against ant predation in the butterfly Smyrna blomfildia. Ecological Entomology, 26:436–439. (View)
11. Machado, G., Freitas, A.V.L. 2001. Larval defence against ant predation in the butterfly Smyrna blomfildia. Ecological Entomology, 26:436–439. (View)
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Larvae of some butterfly species build small trampolines made of feces on the border of leaves. The larva rests on the tip of the trampoline, where it is supposedly protected against ant attacks. We experimentally showed that trampolines indeed work as protection against ants. Moreover, we showed that ants are attracted to the fruits produced by the host plant, so that ant predation on the larvae is more intense in plants bearing fruits.
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10. Machado, G., Giaretta, A.A., Pinto-da-Rocha, R. 2001. Notes on the taxonomy and biology of the Neotropical harvestman Goniosoma catarina sp.n. (Opiliones: Gonyleptidae). Revista Ibérica de Aracnología, 4:17–22. (View)
10. Machado, G., Giaretta, A.A., Pinto-da-Rocha, R. 2001. Notes on the taxonomy and biology of the Neotropical harvestman Goniosoma catarina sp.n. (Opiliones: Gonyleptidae). Revista Ibérica de Aracnología, 4:17–22. (View)
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Most of my non-biologist friends think that “new species” are hard to find. This is definitely not the case for harvestmen. Here we describe a new species, which we named Goniosoma catarina because it occurs in the state of Santa Catarina, Brazil. We also provide some basic information on the behavior of this new species. Individuals form diurnal aggregations, are active mostly at night, and females care for eggs and early hatched nymphs.
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9. Machado, G., Vidal, D.M. 2001. On the occurrence of epizoic cyanobacteria and liverworts on a Neotropical harvestman (Arachnida: Opiliones). Biotropica, 33:535–538. (View)
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Records of “plants” growing on terrestrial animals are incredibly rare. A famous example includes the algae growing on sloth hair. Here we describe algae and moss growing on harvestmen from the Atlantic forest. The fact that individuals of this harvestman species inhabit dump places and live several years as adults may favor “plant” colonization on their dorsum. A key question remains answered: does the presence of a green coverage confer camouflage to the harvestmen?
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8. Machado, G., Raimundo, R.L.G. 2001. Parental investment and the evolution of subsocial behaviour in harvestmen (Arachnida Opiliones). Ethology Ecology & Evolution, 13:133–150. (View)
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We reviewed the forms of parental care in harvestmen and found that the ancestral behavior is to hide eggs in protected places. Egg hiding is associated with production of many small eggs. Maternal and paternal egg attendance has evolved many times independently and is associated with production of few large eggs. We suggest that short ovipositor, long lifespan, and contusive forms of defense may have favored the evolution of egg attendance in some harvestman lineages.
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7. Machado, G., Raimundo, R.L.G., Oliveira, P.S. 2001. Daily activity schedule, gregariousness, and defensive behaviour in the Neotropical harvestman Goniosoma longipes (Opiliones: Gonyleptidae). Journal of Natural History, 34:587–596. (View)
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A harvestman species spends the daylight hours inside caves, sometimes forming aggregations containing as much as 200 individuals. At night, individuals leave the caves to forage on the vegetation. They feed on live and dead invertebrates, which are carried to the cave to be consumed. The main defense mechanisms used by the individuals include falling from the substrate, feigning death, running, pinching the aggressor with leg spines, and releasing strong chemical secretions.
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6. Machado, G., Pizo, M.A. 2001. The use of fruits by the Neotropical harvestman Neosadocus variabilis (Opiliones, Laniatores, Gonyleptidae). Journal of Arachnology, 28:357–360. (View)
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Arachnids are famous by their predacious habitats. Except for some groups of mites, records of plant consumption are scarce among spiders, scorpions, and allies. Here we show that individuals of a harvestman species from the Atlantic forest regularly feed on fallen fruits. Using experimental fruits, we also show that individuals prefer fruits with high lipid contents, which in terms of chemical composition are analogous to the prey used by many harvestman species.
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2000
5. Machado, G., Vasconcellos-Neto, J. 2000. Sperm transfer behavior in the Neotropical scorpion Thestylus glazioui (Scorpiones: Bothriuridae). Revista de Etologia, 2:63–66. (View)
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We were in a field course and found two scorpions during courtship. We recorded the behavior and later we figured out that there was no information on the reproductive biology of species belonging to the genus Thestylus. Although we observed only one courtship sequence, we decided to publish this note to add some behavioral data to the genus. Not surprisingly, the sequence is very similar to other well-studied species of the family Bothriuridae.
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4. Machado, G. 2000. Maternal care in the Neotropical centipede Otostigmus scabricauda (Chilopoda: Scolopendromorpha). Entomological News, 111:250–254. (View)
4. Machado, G. 2000. Maternal care in the Neotropical centipede Otostigmus scabricauda (Chilopoda: Scolopendromorpha). Entomological News, 111:250–254. (View)
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The title of this note is self-explanatory. I describe a case of maternal care in a centipede from Brazil. This finding reinforces the notion that egg attendance is a widespread behavioral trait in a clade of centipedes that includes three orders with unpronounceable names: Craterostigmomorpha, Geophilomorpha, and Scolopendromorpha.
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1998
3. Machado, G., Vasconcelos, C.H.F. 1998. Multi-species aggregations in Neotropical harvestmen (Arachnida: Opiliones: Gonyleptidae). Journal of Arachnology, 26:389–391. (View)
3. Machado, G., Vasconcelos, C.H.F. 1998. Multi-species aggregations in Neotropical harvestmen (Arachnida: Opiliones: Gonyleptidae). Journal of Arachnology, 26:389–391. (View)
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Three harvestman species aggregate together. Whereas species 1 and 2 rarely release chemical defenses, species 3 releases large amounts of strong chemical defenses. We suppose that individuals of species 1 and 2 aggregate close to individuals of species 3 to enjoy the protection afforded by their powerful chemical defenses. Individuals of 3, in turn, may dilute the individual risk of predation aggregating together with individuals of 1 and 2.
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2. Machado, G., Oliveira, P.S. 1998. Reproductive biology of the neotropical harvestman Goniosoma longipes (Arachnida, Opiliones: Gonyleptidae): mating and oviposition behaviour, brood mortality, and parental care. Journal of Zoology, 246:359–367. (View)
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Females of a harvestman species that live inside caves care for their eggs. We showed that maternal protection is crucial to prevent egg predation by conspecific and crickets. However, females are unable to prevent fungi infection on eggs. We found a positive correlation between fungi infection and distance from the clutches to the river that crosses the cave. Thus, it seems that the best way of avoiding fungi infection is to select proper oviposition sites.
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1997
1. Giaretta, A.A., Sawaya, R., Machado, G., Araújo, M.S., Facure, K.G., Medeiros, H.F., Nunes, R. 1997. Diversity and abundance of litter frogs at altitudinal sites at Serra do Japi, Southeastern Brazil. Revista Brasileira de Zoologia, 14:341–346. (View)
1. Giaretta, A.A., Sawaya, R., Machado, G., Araújo, M.S., Facure, K.G., Medeiros, H.F., Nunes, R. 1997. Diversity and abundance of litter frogs at altitudinal sites at Serra do Japi, Southeastern Brazil. Revista Brasileira de Zoologia, 14:341–346. (View)
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When I was an undergraduate student, some friends invited me to help in a fieldwork. We investigated if the density of ground frogs changes along an altitudinal gradient and also in response to the distance from rivers. Frog density was higher in the mountaintop and close to the rivers. Unfortunately, I did not help my friends to analyze the data and write the manuscript because I was ignorant in both tasks. Luckily it changed later!
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Credits of the photos. The numbers refer to the papers listed above. We thank all people that provided these photos to us.
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