Journal articles: 'Sexual selection in animals'

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Janicke, Tim, and Salomé Fromonteil. "Sexual selection and sexual size dimorphism in animals." Biology Letters 17, no. 9 (September 2021): 20210251. http://dx.doi.org/10.1098/rsbl.2021.0251.

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Sexual selection is often considered as a critical evolutionary force promoting sexual size dimorphism (SSD) in animals. However, empirical evidence for a positive relationship between sexual selection on males and male-biased SSD received mixed support depending on the studied taxonomic group and on the method used to quantify sexual selection. Here, we present a meta-analytic approach accounting for phylogenetic non-independence to test how standardized metrics of the opportunity and strength of pre-copulatory sexual selection relate to SSD across a broad range of animal taxa comprising up to 95 effect sizes from 59 species. We found that SSD based on length measurements was correlated with the sex difference in the opportunity for sexual selection but showed a weak and statistically non-significant relationship with the sex difference in the Bateman gradient. These findings suggest that pre-copulatory sexual selection plays a limited role for the evolution of SSD in a broad phylogenetic context.

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Willson, Mary F. "Sexual selection in plants and animals." Trends in Ecology & Evolution 5, no. 7 (July 1990): 210–14. http://dx.doi.org/10.1016/0169-5347(90)90133-x.

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Beilharz, R. G. "Sexual selection: Testing the alternatives." Applied Animal Behaviour Science 22, no. 3-4 (April 1989): 381–83. http://dx.doi.org/10.1016/0168-1591(89)90033-6.

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Knell, Robert J., Darren Naish, Joseph L. Tomkins, and David W. E. Hone. "Sexual selection in prehistoric animals: detection and implications." Trends in Ecology & Evolution 28, no. 1 (January 2013): 38–47. http://dx.doi.org/10.1016/j.tree.2012.07.015.

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Kirkpatrick, M. "Sexual Selection by Female Choice in Polygynous Animals." Annual Review of Ecology and Systematics 18, no. 1 (November 1987): 43–70. http://dx.doi.org/10.1146/annurev.es.18.110187.000355.

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Wellenreuther, Maren, Erik I. Svensson, and Bengt Hansson. "Sexual selection and genetic colour polymorphisms in animals." Molecular Ecology 23, no. 22 (October 13, 2014): 5398–414. http://dx.doi.org/10.1111/mec.12935.

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Bell, Rayna C., and Kelly R. Zamudio. "Sexual dichromatism in frogs: natural selection, sexual selection and unexpected diversity." Proceedings of the Royal Society B: Biological Sciences 279, no. 1748 (September 19, 2012): 4687–93. http://dx.doi.org/10.1098/rspb.2012.1609.

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Sexual dichromatism, a form of sexual dimorphism in which males and females differ in colour, is widespread in animals but has been predominantly studied in birds, fishes and butterflies. Moreover, although there are several proposed evolutionary mechanisms for sexual dichromatism in vertebrates, few studies have examined this phenomenon outside the context of sexual selection. Here, we describe unexpectedly high diversity of sexual dichromatism in frogs and create a comparative framework to guide future analyses of the evolution of these sexual colour differences. We review what is known about evolution of colour dimorphism in frogs, highlight alternative mechanisms that may contribute to the evolution of sexual colour differences, and compare them to mechanisms active in other major groups of vertebrates. In frogs, sexual dichromatism can be dynamic (temporary colour change in males) or ontogenetic (permanent colour change in males or females). The degree and the duration of sexual colour differences vary greatly across lineages, and we do not detect phylogenetic signal in the distribution of this trait, therefore frogs provide an opportunity to investigate the roles of natural and sexual selection across multiple independent derivations of sexual dichromatism.

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Greeff, J. M., and N. K. Michiels. "Low potential for sexual selection in simultaneously hermaphroditic animals." Proceedings of the Royal Society of London. Series B: Biological Sciences 266, no. 1429 (August 22, 1999): 1671–76. http://dx.doi.org/10.1098/rspb.1999.0830.

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Hare, Robin M., and Leigh W. Simmons. "Sexual selection and its evolutionary consequences in female animals." Biological Reviews 94, no. 3 (November 28, 2018): 929–56. http://dx.doi.org/10.1111/brv.12484.

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Serpell, James. "Anthropomorphism and Anthropomorphic Selection—Beyond the "Cute Response"." Society & Animals 10, no. 4 (2002): 437–54. http://dx.doi.org/10.1163/156853002320936926.

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AbstractThis article explores the origin and evolutionary implications of anthropomorphism in the context of our relationships with animal companions. On the human side, anthropomorphic thinking enables animal companions' social behavior to be construed in human terms, thereby allowing these nonhuman animals to function for their human owners or guardians as providers of nonhuman social support. Absence of social support is known to be detrimental to human health and well being. Therefore, anthropomorphism and its corollary, pet keeping, have obvious biological fitness implications. On the animal side, anthropomorphism constitutes a unique evolutionary selection pressure, analogous to sexual selection, which has molded the appearance, anatomy, and behavior of companion animal species so as to adapt them to their unusual ecological niche as social support providers. Although such species undoubtedly have benefited numerically from the effects of this process, the consequences of anthropomorphism are less benign when viewed from the perspective of individual animals. Indeed, anthropomorphic selection probably is responsible for some of the more severe welfare problems currently found in companion animals.

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Serpell, James. "Anthropomorphism and Anthropomorphic Selection—Beyond the "Cute Response"." Society & Animals 11, no. 1 (2003): 83–100. http://dx.doi.org/10.1163/156853003321618864.

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AbstractThis article explores the origin and evolutionary implications of anthropomorphism in the context of our relationships with animal companions. On the human side, anthropomorphic thinking enables animal companions' social behavior to be construed in human terms, thereby allowing these nonhuman animals to function for their human owners or guardians as providers of nonhuman social support. Absence of social support is known to be detrimental to human health and well being. Therefore, anthropomorphism and its corollary, pet keeping, have obvious biological fitness implications. On the animal side, anthropomorphism constitutes a unique evolutionary selection pressure, analogous to sexual selection, which has molded the appearance, anatomy, and behavior of companion animal species so as to adapt them to their unusual ecological niche as social support providers. Although such species undoubtedly have benefited numerically from the effects of this process, the consequences of anthropomorphism are less benign when viewed from the perspective of individual animals. Indeed, anthropomorphic selection probably is responsible for some of the more severe welfare problems currently found in companion animals.

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Evans, Jonathan P., and Rowan A. Lymbery. "Sexual selection after gamete release in broadcast spawning invertebrates." Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1813 (October 19, 2020): 20200069. http://dx.doi.org/10.1098/rstb.2020.0069.

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Broadcast spawning invertebrates offer highly tractable models for evaluating sperm competition, gamete-level mate choice and sexual conflict. By displaying the ancestral mating strategy of external fertilization, where sexual selection is constrained to act after gamete release, broadcast spawners also offer potential evolutionary insights into the cascade of events that led to sexual reproduction in more ‘derived’ groups (including humans). Moreover, the dynamic reproductive conditions faced by these animals mean that the strength and direction of sexual selection on both males and females can vary considerably. These attributes make broadcast spawning invertebrate systems uniquely suited to testing, extending, and sometimes challenging classic and contemporary ideas in sperm competition, many of which were first captured in Parker's seminal papers on the topic. Here, we provide a synthesis outlining progress in these fields, and highlight the burgeoning potential for broadcast spawners to provide both evolutionary and mechanistic understanding into gamete-level sexual selection more broadly across the animal kingdom. This article is part of the theme issue ‘Fifty years of sperm competition’.

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Schärer, Lukas, and Tim Janicke. "Sex allocation and sexual conflict in simultaneously hermaphroditic animals." Biology Letters 5, no. 5 (April 2009): 705–8. http://dx.doi.org/10.1098/rsbl.2009.0100.

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Links between sex allocation (SA) and sexual conflict in simultaneous hermaphrodites have been evident since Charnov's landmark paper published 30 years ago. We discuss two links, namely the potential for sexual conflict over SA between sperm donor and recipient, and the importance of post-copulatory sexual selection and the resulting sexual conflict for the evolution of SA. We cover the little empirical and theoretical work exploring these links, and present an experimental test of one theoretical prediction. The link between SA and sexual conflict is an interesting field for future empirical and theoretical research.

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Simmons, Leigh W., and Francisco Garcia-Gonzalez. "Can Sexual Selection Drive the Evolution of Sperm Cell Structure?" Cells 10, no. 5 (May 17, 2021): 1227. http://dx.doi.org/10.3390/cells10051227.

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Sperm cells have undergone an extraordinarily divergent evolution among metazoan animals. Parker recognized that because female animals frequently mate with more than one male, sexual selection would continue after mating and impose strong selection on sperm cells to maximize fertilization success. Comparative analyses among species have revealed a general relationship between the strength of selection from sperm competition and the length of sperm cells and their constituent parts. However, comparative analyses cannot address causation. Here, we use experimental evolution to ask whether sexual selection can drive the divergence of sperm cell phenotype, using the dung beetle Onthophagus taurus as a model. We either relaxed sexual selection by enforcing monogamy or allowed sexual selection to continue for 20 generations before sampling males and measuring the total length of sperm cells and their constituent parts, the acrosome, nucleus, and flagella. We found differences in the length of the sperm cell nucleus but no differences in the length of the acrosome, flagella, or total sperm length. Our data suggest that different sperm cell components may respond independently to sexual selection and contribute to the divergent evolution of these extraordinary cells.

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Schuett, Wiebke, Tom Tregenza, and Sasha R. X. Dall. "Sexual selection and animal personality." Biological Reviews 85, no. 2 (May 2010): 217–46. http://dx.doi.org/10.1111/j.1469-185x.2009.00101.x.

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Méndez, Vivian, and Alex Córdoba-Aguilar. "Sexual selection and animal genitalia." Trends in Ecology & Evolution 19, no. 5 (May 2004): 224–25. http://dx.doi.org/10.1016/j.tree.2004.03.012.

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17

Cooper, W. E., and Malte Andersson. "Sexual Selection." Copeia 1995, no. 3 (August 18, 1995): 756. http://dx.doi.org/10.2307/1446782.

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Hare, Robin M., and Leigh W. Simmons. "Sexual selection maintains a female-specific character in a species with dynamic sex roles." Behavioral Ecology 32, no. 4 (March 25, 2021): 609–16. http://dx.doi.org/10.1093/beheco/arab005.

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Abstract The effects of sexual selection are more conspicuous among male animals, and, as a result, the majority of sexual selection research focuses on males. However, burgeoning evidence suggests that sexual selection also acts on females, and there have been calls for an increased focus on females. Here, we used a multivariate approach to analyze sexual selection in Kawanaphila nartee, a spermatophore gift-giving bushcricket with dynamic sex roles. Early in the breeding season, females compete for males, and, later, when environmental food resources are more abundant, sex roles revert to Darwinian convention. Ear size, which is much greater in females than in males, has been suggested to affect female fitness as females with larger ears are more likely to reach calling males first under sex-role-reversed conditions. We tested this suggestion and found evidence of positive linear and nonlinear correlational selection acting on female ear size early in the breeding season (under reversed sex roles) but not later in the breeding season (under Darwinian sex roles). Interestingly, there was no correlation between mating success and reproductive success (Bateman gradient) at any time during the season. Together, our results indicate that even brief and circumscribed periods of intrasexual competition among females can lead to sexual selection on morphological characters and that this selection may not depend on multiple mating. Considering the wealth of reports in the literature of brief episodes of intrasexual competition among female animals, we recommend increased study of sexual selection acting on females.

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Stockley, Paula, Catarina Franco, Amy J. Claydon, Amanda Davidson, Dean E. Hammond, Philip J. Brownridge, Jane L. Hurst, and Robert J. Beynon. "Revealing mechanisms of mating plug function under sexual selection." Proceedings of the National Academy of Sciences 117, no. 44 (October 19, 2020): 27465–73. http://dx.doi.org/10.1073/pnas.1920526117.

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Mating plugs are produced by many sexually reproducing animals and are hypothesized to promote male fertilization success under promiscuous mating. However, tests of this hypothesis have been constrained by an inability to discriminate ejaculates of different males in direct competition. Here, we use stable isotope labeling in vivo and proteomics to achieve this in a promiscuous rodent,Myodes glareolus. We show that, although the first male’s plug is usually dislodged, it can be retained throughout the second male’s copulation. Retained plugs did not completely block rival sperm but did significantly limit their numbers. Differences in the number of each male’s sperm progressing through the female reproductive tract were also explained by natural variation in the size of mating plugs and reproductive accessory glands from which major plug proteins originate. Relative sperm numbers in turn predicted the relative fertilization success of rival males. Our application of stable isotopes to label ejaculates resolves a longstanding debate by revealing how rodent mating plugs promote fertilization success under competitive conditions. This approach opens new opportunities to reveal cryptic mechanisms of postcopulatory sexual selection among diverse animal taxa.

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Tobias, Joseph A., Robert Montgomerie, and Bruce E. Lyon. "The evolution of female ornaments and weaponry: social selection, sexual selection and ecological competition." Philosophical Transactions of the Royal Society B: Biological Sciences 367, no. 1600 (August 19, 2012): 2274–93. http://dx.doi.org/10.1098/rstb.2011.0280.

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Ornaments, weapons and aggressive behaviours may evolve in female animals by mate choice and intrasexual competition for mating opportunities—the standard forms of sexual selection in males. However, a growing body of evidence suggests that selection tends to operate in different ways in males and females, with female traits more often mediating competition for ecological resources, rather than mate acquisition. Two main solutions have been proposed to accommodate this disparity. One is to expand the concept of sexual selection to include all mechanisms related to fecundity; another is to adopt an alternative conceptual framework—the theory of social selection—in which sexual selection is one component of a more general form of selection resulting from all social interactions. In this study, we summarize the history of the debate about female ornaments and weapons, and discuss potential resolutions. We review the components of fitness driving ornamentation in a wide range of systems, and show that selection often falls outside the limits of traditional sexual selection theory, particularly in females. We conclude that the evolution of these traits in both sexes is best understood within the unifying framework of social selection.

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LORENZI, M. C., and G. SELLA. "A measure of sexual selection in hermaphroditic animals: parentage skew and the opportunity for selection." Journal of Evolutionary Biology 21, no. 3 (May 2008): 827–33. http://dx.doi.org/10.1111/j.1420-9101.2008.01513.x.

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Krüger, O., N. B. Davies, and M. D. Sorenson. "The evolution of sexual dimorphism in parasitic cuckoos: sexual selection or coevolution?" Proceedings of the Royal Society B: Biological Sciences 274, no. 1617 (April 17, 2007): 1553–60. http://dx.doi.org/10.1098/rspb.2007.0281.

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Sexual dimorphism is ubiquitous in animals and can result from selection pressure on one or both sexes. Sexual selection has become the predominant explanation for the evolution of sexual dimorphism, with strong selection on size-related mating success in males being the most common situation. The cuckoos (family Cuculidae) provide an exceptional case in which both sexes of many species are freed from the burden of parental care but where coevolution between parasitic cuckoos and their hosts also results in intense selection. Here, we show that size and plumage differences between the sexes in parasitic cuckoos are more likely the result of coevolution than sexual selection. While both sexes changed in size as brood parasitism evolved, we find no evidence for selection on males to become larger. Rather, our analysis indicates stronger selection on parasitic females to become smaller, resulting in a shift from dimorphism with larger females in cuckoos with parental care to dimorphism with larger males in parasitic species. In addition, the evolution of brood parasitism was associated with more cryptic plumage in both sexes, but especially in females, a result that contrasts with the strong plumage dimorphism seen in some other parasitic birds. Examination of the three independent origins of brood parasitism suggests that different parasitic cuckoo lineages followed divergent evolutionary pathways to successful brood parasitism. These results argue for the powerful role of parasite–host coevolution in shaping cuckoo life histories in general and sexual dimorphism in particular.

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Murray, Rosalind L., Darryl T. Gwynne, and Luc F. Bussière. "Mating and Sexual Selection in Empidine Dance Flies (Empididae)." Insects 13, no. 9 (September 15, 2022): 839. http://dx.doi.org/10.3390/insects13090839.

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Species whose behaviour or morphology diverges from typical patterns can provide unique insights on the evolutionary forces that promote diversity. Darwin recognised that while elaborate sexually selected traits mostly occurred among males, in a few species females possess such traits. Some species from the subfamily Empidinae (Diptera: Empididae) are among the animals that are often invoked to illustrate female ornaments. Empidines include taxa that exhibit varying levels of female ornament expression; some species possess multiple, elaborate female-specific ornaments while others have fewer and more modest adornments, and many species are altogether lacking discernible sexual ornamentation. This continuous variation in display traits in the Empidinae provides unique opportunities to explore the causes and consequences of sexually selected ornament expression. Here, we review the literature on sexual selection and mating systems in these flies and synthesise the evidence for various evolutionary forces that could conceivably create this impressive morphological and behavioural diversity, despite evolutionary constraints on female ornament exaggeration that help to explain its general rarity among animals. We also suggest some aspects of diversity that remain relatively unexplored or poorly understood, and close by offering suggestions for future research progress in the evolutionary ecology of mating behaviour among empidine flies.

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Lakhani, Leena. "PROTECTIVE COLORATION IN ANIMALS." International Journal of Research -GRANTHAALAYAH 2, no. 3SE (December 31, 2014): 1–5. http://dx.doi.org/10.29121/granthaalayah.v2.i3se.2014.3515.

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Animals have range of defensive markings which helps to the risk of predator detection (camouflage), warn predators of the prey’s unpalatability (aposematism) or fool a predator into mimicry, masquerade. Animals also use colors in advertising, signalling services such as cleaning to animals of other species, to signal sexual status to other members of the same species. Some animals use color to divert attacks by startle (dalmatic behaviour), surprising a predator e.g. witheyespots or other flashes of color or possibly by motion dazzle, confusing a predator attack by moving a bold pattern like zebra stripes. Some animals are colored for physical protection, such as having pigments in the skin to protect against sunburn; some animals can lighten or darken their skin for temperature regulation. This adaptive mechanism is known as protective coloration. After several years of evolution, most animals now achieved the color pattern most suited for their natural habitat and role in the food chains. Animals in the world rely on their coloration for either protection from predators, concealment from prey or sexual selection. In general the purpose of protective coloration is to decrease an organism’s visibility or to alter its appearance to other organisms. Sometimes several forms of protective coloration are superimposed on one animal.

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Fox, Stanley F., Felipe De Jesús Rodríguez-Romero, and Andrea Acevedo Crosby. "Juvenile-juvenile social signalling: a case for precocial sexual selection in the collared lizard, Crotaphytus collaris (Squamata: Crotaphytidae)?" Biological Journal of the Linnean Society 130, no. 2 (May 18, 2020): 336–44. http://dx.doi.org/10.1093/biolinnean/blaa045.

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Abstract Sexual selection is widespread in animals, but quite naturally studied in adults. Juvenile males in most animals are not differentiated from females and coloration is usually drab. However, there is no reason to suspect that sexual differences cannot develop before puberty, influence social interactions, and then have fitness pay-offs later in life. Juvenile collared lizards (Crotaphytus collaris (Say, 1822)) show marked dichromatism: males develop bright dorsolateral orange bars whereas females do not. These juvenile orange bars (JOB) disappear at sexual maturity, when males develop different colour traits maintained by sexual selection. We conducted field experiments with juvenile males on their developing territories in which we utilized staged intruders of juvenile males (with JOB) and juvenile females (lacking JOB) and also juvenile male intruders whose JOB were manipulated. Residents reacted significantly more aggressively toward males vs. females, and also toward males whose JOB were emphasized with paint than those whose JOB were masked by paint. These JOB are used in signalling among juveniles and we suggest the social relations established then are retained until sexual maturation the next spring (after the JOB are lost) to benefit males that previously displayed strong JOB by increased matings in the spring as sexually mature yearlings as per a phenomenon we call precocial sexual selection.

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Fernandes Júnior, Gerardo Alves, Delvan Alves Silva, Lucio Flavio Macedo Mota, Thaise Pinto de Melo, Larissa Fernanda Simielli Fonseca, Danielly Beraldo dos Santos Silva, Roberto Carvalheiro, and Lucia Galvão Albuquerque. "Sustainable Intensification of Beef Production in the Tropics: The Role of Genetically Improving Sexual Precocity of Heifers." Animals 12, no. 2 (January 12, 2022): 174. http://dx.doi.org/10.3390/ani12020174.

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Increasing productivity through continued animal genetic improvement is a crucial part of implementing sustainable livestock intensification programs. In Zebu cattle, the lack of sexual precocity is one of the main obstacles to improving beef production efficiency. Puberty-related traits are complex, but large-scale data sets from different “omics” have provided information on specific genes and biological processes with major effects on the expression of such traits, which can greatly increase animal genetic evaluation. In addition, genetic parameter estimates and genomic predictions involving sexual precocity indicator traits and productive, reproductive, and feed-efficiency related traits highlighted the feasibility and importance of direct selection for anticipating heifer reproductive life. Indeed, the case study of selection for sexual precocity in Nellore breeding programs presented here show that, in 12 years of selection for female early precocity and improved management practices, the phenotypic means of age at first calving showed a strong decreasing trend, changing from nearly 34 to less than 28 months, with a genetic trend of almost −2 days/year. In this period, the percentage of early pregnancy in the herds changed from around 10% to more than 60%, showing that the genetic improvement of heifer’s sexual precocity allows optimizing the productive cycle by reducing the number of unproductive animals in the herd. It has a direct impact on sustainability by better use of resources. Genomic selection breeding programs accounting for genotype by environment interaction represent promising tools for accelerating genetic progress for sexual precocity in tropical beef cattle.

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Arnold, Stevan J. "Bateman's Principles and the Measurement of Sexual Selection in Plants and Animals." American Naturalist 144 (August 1994): S126—S149. http://dx.doi.org/10.1086/285656.

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Cutter, Asher D. "Reproductive transitions in plants and animals: selfing syndrome, sexual selection and speciation." New Phytologist 224, no. 3 (August 18, 2019): 1080–94. http://dx.doi.org/10.1111/nph.16075.

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Fitzpatrick, Courtney L. "Expanding Sexual Selection Gradients; A Synthetic Refinement of Sexual Selection Theory." Ethology 121, no. 3 (January 23, 2015): 207–17. http://dx.doi.org/10.1111/eth.12352.

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Beekman, Madeleine, Bart Nieuwenhuis, Daniel Ortiz-Barrientos, and Jonathan P. Evans. "Sexual selection in hermaphrodites, sperm and broadcast spawners, plants and fungi." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1706 (October 19, 2016): 20150541. http://dx.doi.org/10.1098/rstb.2015.0541.

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Darwin was the first to recognize that sexual selection is a strong evolutionary force. Exaggerated traits allow same-sex individuals to compete over access to mates and provide a mechanism by which mates are selected. It is relatively easy to appreciate how inter- and intrasexual selection work in organisms with the sensory capabilities to perceive physical or behavioural traits that signal mate quality or mate compatibility, and to assess the relative quality of competitors. It is therefore not surprising that most studies of sexual selection have focused on animals with separate sexes and obvious adaptations that function in the context of reproductive competition. Yet, many sexual organisms are both male and female at the same time, often lack sexual dimorphism and never come into direct contact at mating. How does sexual selection act in such species, and what can we learn from them? Here, we address these questions by exploring the potential for sexual selection in simultaneous hermaphrodites, sperm- and broadcast spawners, plants and fungi. Our review reveals a range of mechanisms of sexual selection, operating primarily after gametes have been released, which are common in many of these groups and also quite possibly in more familiar (internally fertilizing and sexually dimorphic) organisms. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

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Abbott, Jessica K. "Intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic animals." Proceedings of the Royal Society B: Biological Sciences 278, no. 1703 (August 18, 2010): 161–69. http://dx.doi.org/10.1098/rspb.2010.1401.

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Intra-locus sexual conflict results when sex-specific selection pressures for a given trait act against the intra-sexual genetic correlation for that trait. It has been found in a wide variety of taxa in both laboratory and natural populations, but the importance of intra-locus sexual conflict and sexually antagonistic genetic variation in hermaphroditic organisms has rarely been considered. This is not so surprising given the conceptual and theoretical association of intra-locus sexual conflict with sexual dimorphism, but there is no a priori reason why intra-locus sexual conflict cannot occur in hermaphroditic organisms as well. Here, I discuss the potential for intra-locus sexual conflict in hermaphroditic animals and review the available evidence for such conflict, and for the existence of sexually antagonistic genetic variation in hermaphrodites. I argue that mutations with asymmetric effects are particularly likely to be important in mediating sexual antagonism in hermaphroditic organisms. Moreover, sexually antagonistic genetic variation is likely to play an important role in inter-individual variation in sex allocation and in transitions to and from gonochorism (separate sexes) in simultaneous hermaphrodites. I also describe how sequential hermaphrodites may experience a unique form of intra-locus sexual conflict via antagonistic pleiotropy. Finally, I conclude with some suggestions for further research.

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Schärer, Lukas, and Ido Pen. "Sex allocation and investment into pre- and post-copulatory traits in simultaneous hermaphrodites: the role of polyandry and local sperm competition." Philosophical Transactions of the Royal Society B: Biological Sciences 368, no. 1613 (March 5, 2013): 20120052. http://dx.doi.org/10.1098/rstb.2012.0052.

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Sex allocation theory predicts the optimal allocation to male and female reproduction in sexual organisms. In animals, most work on sex allocation has focused on species with separate sexes and our understanding of simultaneous hermaphrodites is patchier. Recent theory predicts that sex allocation in simultaneous hermaphrodites should strongly be affected by post-copulatory sexual selection, while the role of pre-copulatory sexual selection is much less clear. Here, we review sex allocation and sexual selection theory for simultaneous hermaphrodites, and identify several strong and potentially unwarranted assumptions. We then present a model that treats allocation to sexually selected traits as components of sex allocation and explore patterns of allocation when some of these assumptions are relaxed. For example, when investment into a male sexually selected trait leads to skews in sperm competition, causing local sperm competition, this is expected to lead to a reduced allocation to sperm production. We conclude that understanding the evolution of sex allocation in simultaneous hermaphrodites requires detailed knowledge of the different sexual selection processes and their relative importance. However, little is currently known quantitatively about sexual selection in simultaneous hermaphrodites, about what the underlying traits are, and about what drives and constrains their evolution. Future work should therefore aim at quantifying sexual selection and identifying the underlying traits along the pre- to post-copulatory axis.

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Cassini, Marcelo H. "Sexual size dimorphism and sexual selection in primates." Mammal Review 50, no. 3 (April 7, 2020): 231–39. http://dx.doi.org/10.1111/mam.12191.

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Simpson, Richard K., Allison F. Mistakidis, and Stéphanie M. Doucet. "Natural and sexual selection shape the evolution of colour and conspicuousness in North American wood-warblers (Parulidae)." Biological Journal of the Linnean Society 130, no. 1 (March 10, 2020): 89–100. http://dx.doi.org/10.1093/biolinnean/blaa015.

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Abstract Natural and sexual selection drive colour evolution in animals. However, these different selective forces are often studied independently or without considering environmental variation. We evaluated the roles of natural and sexual selection together on colour evolution in 15 sympatric wood-warbler species, while considering the influence of variation in the light environment and visual background. We tested the influence of each selective pressure on male and female coloration and contrast against the background using avian visual models in phylogenetically controlled analyses. We found natural and sexual selection simultaneously driving cryptic and conspicuous plumage in males by acting on different body regions. For example, we found that ground-nesting species had males with conspicuous under-body plumage and cryptic upper-body plumage, showing how natural and sexual selection can drive colour evolution concordantly. We also found interesting relationships with female plumage, such as nest predation positively covarying with female contrast against the background, suggesting a cost to female conspicuousness. Our findings here showcase the complexity of selection on coloration and illustrate the importance of: (1) accounting for environmental variation when assessing how natural and sexual selection drive colour evolution; and (2) testing how multiple selection pressures are shaping colour diversity among species.

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35

Alcock, John. "Sexual Selection and Animal Genitalia.William G. Eberhard." Quarterly Review of Biology 62, no. 1 (March 1987): 100. http://dx.doi.org/10.1086/415342.

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Clutton-Brock, Tim. "Sexual selection in females." Animal Behaviour 77, no. 1 (January 2009): 3–11. http://dx.doi.org/10.1016/j.anbehav.2008.08.026.

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Bernstein, Irwin S. "Theories of sexual selection." American Journal of Primatology 65, no. 3 (2005): 295–99. http://dx.doi.org/10.1002/ajp.20109.

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Levine, Louis. "Sexual selection does not equal mate selection." Animal Behaviour 33, no. 4 (November 1985): 1363–64. http://dx.doi.org/10.1016/s0003-3472(85)80200-1.

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Ugnivenko, A. M., and L. A. Koropets. "INFLUENCE OF BULL’S BODY TYPES AND MEAT FORMS EXPRESSION ON THEIR SEXUAL ACTIVITY." Animal Science and Food Technology 12, no. 1 (March 2021): 56–61. http://dx.doi.org/10.31548/animal2021.01.056.

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In beef cattle breeding, the reproductive capacity of bulls significantly affects the economic efficiency of production. Selection for the meat productivity can negatively affect the ability of bulls to reproduce, so it is necessary to consider the risks of such a connection when selecting them. The study determined the rate of manifestation of Ukrainian beef breed bulls sexual reflexes of different body types and severity of meat forms. According to the type of body structure of bulls divided into two groups: large (high and long-bodied) and compact (low and short-bodied). The distribution performed using the growth index. The severity of meat forms of bulls was determined at 15 months of age on a 60-point scale. The animals on meat forms divided into two groups compared with the average score of experimental bulls. The degree of sexual activity manifestation assessed by the duration of sexual reflexes from bringing the bools to the stuffed animal to the mating attempt. According to the manifestation of libido, animals divided into three groups: active – mating attempt to cage from 10 to 60 seconds, moderate – from 60 to 120 seconds and slow – the time before the mating attempt lasted more than 120 seconds. Subsequently, in experimental bulls recorded the duration of productive use period, the number of leads to the stuffed animal and mating attempts to it and the number of received and rejected ejaculates. It found that the tendency of the distribution of active moderate and slow manifestation of sexual reflexes in bulls of different body types and development of meat forms is similar. In bulls of different groups, moderate sexual activity most often observed, but specific tendencies observed within the groups. The share of high sexual activity was higher in compact bulls compared to large coeval animals. Among animals grouped by the development of meat forms, the share of high sexual activity higher in bulls with better expressed meat forms. In the future, large bulls tend to increase the duration of productive use, predominate in the share of mating attempt and are characterized by a decrease in the share of ejaculate culling. Bulls with better meat forms tend to increase the duration of productive use due to their higher breeding value in terms of meat productivity. No difference was found in the proportion of mating attempts and the percentage of culled ejaculates between animals with different manifestations of meat forms. The obtained results prove that for intensive use at a young age more suitable bulls of compact type, and in adulthood more effective large sires. Better development of meat forms somewhat reduces the sexual activity of young bulls. At a more mature age, the results of the use of bulls are practically unaffected by meat forms.

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Ugnivenko, A. M., and L. A. Koropets. "INFLUENCE OF BULL’S BODY TYPES AND MEAT FORMS EXPRESSION ON THEIR SEXUAL ACTIVITY." Animal Science and Food Technology 12, no. 1 (March 2021): 56–61. http://dx.doi.org/10.31548/animal2021.01.056.

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Abstract:

In beef cattle breeding, the reproductive capacity of bulls significantly affects the economic efficiency of production. Selection for the meat productivity can negatively affect the ability of bulls to reproduce, so it is necessary to consider the risks of such a connection when selecting them. The study determined the rate of manifestation of Ukrainian beef breed bulls sexual reflexes of different body types and severity of meat forms. According to the type of body structure of bulls divided into two groups: large (high and long-bodied) and compact (low and short-bodied). The distribution performed using the growth index. The severity of meat forms of bulls was determined at 15 months of age on a 60-point scale. The animals on meat forms divided into two groups compared with the average score of experimental bulls. The degree of sexual activity manifestation assessed by the duration of sexual reflexes from bringing the bools to the stuffed animal to the mating attempt. According to the manifestation of libido, animals divided into three groups: active – mating attempt to cage from 10 to 60 seconds, moderate – from 60 to 120 seconds and slow – the time before the mating attempt lasted more than 120 seconds. Subsequently, in experimental bulls recorded the duration of productive use period, the number of leads to the stuffed animal and mating attempts to it and the number of received and rejected ejaculates. It found that the tendency of the distribution of active moderate and slow manifestation of sexual reflexes in bulls of different body types and development of meat forms is similar. In bulls of different groups, moderate sexual activity most often observed, but specific tendencies observed within the groups. The share of high sexual activity was higher in compact bulls compared to large coeval animals. Among animals grouped by the development of meat forms, the share of high sexual activity higher in bulls with better expressed meat forms. In the future, large bulls tend to increase the duration of productive use, predominate in the share of mating attempt and are characterized by a decrease in the share of ejaculate culling. Bulls with better meat forms tend to increase the duration of productive use due to their higher breeding value in terms of meat productivity. No difference was found in the proportion of mating attempts and the percentage of culled ejaculates between animals with different manifestations of meat forms. The obtained results prove that for intensive use at a young age more suitable bulls of compact type, and in adulthood more effective large sires. Better development of meat forms somewhat reduces the sexual activity of young bulls. At a more mature age, the results of the use of bulls are practically unaffected by meat forms.

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Janicke, Tim, Ines K. Häderer, Marc J. Lajeunesse, and Nils Anthes. "Darwinian sex roles confirmed across the animal kingdom." Science Advances 2, no. 2 (February 2016): e1500983. http://dx.doi.org/10.1126/sciadv.1500983.

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Since Darwin’s conception of sexual selection theory, scientists have struggled to identify the evolutionary forces underlying the pervasive differences between male and female behavior, morphology, and physiology. The Darwin-Bateman paradigm predicts that anisogamy imposes stronger sexual selection on males, which, in turn, drives the evolution of conventional sex roles in terms of female-biased parental care and male-biased sexual dimorphism. Although this paradigm forms the cornerstone of modern sexual selection theory, it still remains untested across the animal tree of life. This lack of evidence has promoted the rise of alternative hypotheses arguing that sex differences are entirely driven by environmental factors or chance. We demonstrate that, across the animal kingdom, sexual selection, as captured by standard Bateman metrics, is indeed stronger in males than in females and that it is evolutionarily tied to sex biases in parental care and sexual dimorphism. Our findings provide the first comprehensive evidence that Darwin’s concept of conventional sex roles is accurate and refute recent criticism of sexual selection theory.

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Yan, Zhi-Chao, Guang-Yuan Qi, Tian-Yi Yao, and Yuan-Xi Li. "Mitochondrial Genomes of Two Asexual Trichogramma (Hymenoptera: Trichogrammatidae) Strains and Comparison with Their Sexual Relatives." Insects 13, no. 6 (June 16, 2022): 549. http://dx.doi.org/10.3390/insects13060549.

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Despite its substantial costs, sexual reproduction dominates in animals. One popular explanation for the paradox of sex is that asexual reproduction is more likely to accumulate deleterious mutations than sexual reproduction. To test this hypothesis, we compared the mitogenomes of two asexual wasp strains, Trichogramma cacoeciae and T. pretiosum, to their sexual relatives. These two asexual strains represent two different transition mechanisms in Trichogramma from sexual to asexual reproduction. Asexual T. pretiosum is induced by Wolbachia, while T. cacoeciae presumably originated from interspecific hybridization. We sequenced and assembled complete mitochondrial genomes of asexual T. cacoeciae and T. pretiosum. Compared to four sexual relatives, we found no evidence of higher mutation accumulation in asexual Trichogramma mitogenomes than in their sexual relatives. We also did not detect any relaxed selection in asexual Trichogramma mitogenomes. In contrast, the intensified selection was detected in Nad1 and Nad4 of the asexual T. pretiosum mitogenome, suggesting more purifying selection. In summary, no higher mitochondrial mutation accumulation was detected in these two asexual Trichogramma strains. This study provides a basis for further investigating mitochondrial evolution and asexual reproduction in Trichogramma.

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Kozyr, V., and V. Barabash. "Influence of natural selection on the reproductive function of bulls." Agricultural Science and Practice 4, no. 1 (April 15, 2017): 20–27. http://dx.doi.org/10.15407/agrisp4.01.020.

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Aim. To investigate the infl uence of natural selection of bulls during tethered and non-tethered keeping on their reproductive function. Methods. Observation of analogue groups in different conditions of keeping, yet with the identical level of feeding and using, ethological methods of the behavior of animals in a herd and in a “mini- herd”, zootechnical, genetic-mathematical, biometric and modelling methods. Results. It was established that dominant animals in the herd oppress the sexual ability of their subordinates, causing the decrease in their libido, erection, quality of sperm (as far as to the impotence). Conclusions. The infl uence of natural selection on the sexual potency of breeding bulls during their non-tethered keeping and some ethological specifi cities during the tethered keeping were established along with the reactions of an organism depending on the type of body composition and build. The application of the revealed regularities facilitates the work regarding the selection of bulls while evaluating the quality of the sperm production and ensuring the increase in the number of their offspring in further generations.

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Hodge, J. R., F. Santini, and P. C. Wainwright. "Colour dimorphism in labrid fishes as an adaptation to life on coral reefs." Proceedings of the Royal Society B: Biological Sciences 287, no. 1923 (March 18, 2020): 20200167. http://dx.doi.org/10.1098/rspb.2020.0167.

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Conspicuous coloration displayed by animals that express sexual colour dimorphism is generally explained as an adaptation to sexual selection, yet the interactions and relative effects of selective forces influencing colour dimorphism are largely unknown. Qualitatively, colour dimorphism appears more pronounced in marine fishes that live on coral reefs where traits associated with strong sexual selection are purportedly more common. Using phylogenetic comparative analysis, we show that wrasses and parrotfishes exclusive to coral reefs are the most colour dimorphic, but surprisingly, the effect of habitat is not influenced by traits associated with strong sexual selection. Rather, habitat-specific selective forces, including clear water and structural refuge, promote the evolution of pronounced colour dimorphism that manifests colours less likely to be displayed in other habitats. Our results demonstrate that environmental context ultimately determines the evolution of conspicuous coloration in colour-dimorphic labrid fishes, despite other influential selective forces.

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Herrera, Emilio A., and Yarlenis Castro. "Trypanosoma evansi (Kinetoplastida: Trypanosomatidae) in capybaras (Hydrochoerus hydrochaeris, Rodentia: Hydrochoeridae): prevalence, effect and sexual selection." Revista de Biología Tropical 65, no. 1 (January 9, 2017): 229. http://dx.doi.org/10.15517/rbt.v64i3.20110.

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Parasites play a crucial role in the ecology of animals. They also appear to be important in mechanisms underlying sexual selection processes. In this article we study the prevalence, effect and potential role in sexual selection of the protozoon Trypanosoma evansi in capybaras, Hydrochoerus hydrochaeris. We collected our samples from the annual capybara cull of a ranch in Venezuela, using the volume of the snout scent gland as an indicator of dominance; the residuals of body weight as indicators of condition; and the residuals of the spleen mass as indicators of immune function. Overall prevalence was 30.9% (N=97) with no difference between males and females and no relation between infection with T. evansi and condition. However, we found that infected animals had larger spleens (residuals), indicating an immunological cost of the infection. Further, males with larger snout scent glands (more dominant) were less likely to be infected than males with smaller glands (less dominant) suggesting that by choosing males with a large gland, females may be using the gland as an indicator of health, which is consistent with the “good genes” view of sexual selection.

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Herring, Peter J. "REVIEW. Sex with the lights on? A review of bioluminescent sexual dimorphism in the sea." Journal of the Marine Biological Association of the United Kingdom 87, no. 4 (July 30, 2007): 829–42. http://dx.doi.org/10.1017/s0025315407056433.

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The reflected patterns and colours of terrestrial animals often show a sexual dimorphism associated with visual display, mate recognition and selection. In the sea the structures associated with bioluminescence may also show a marked sexual dimorphism. Some apparent bioluminescent dimorphisms (e.g. differences in photophore numbers) are probably secondary functions of sexual differences in size. A role in sexual communication is much more likely where specific photophores are developed or enlarged in mature specimens of one sex only but the presence of light organs in female anglerfishes (but not in males) is complicated by a significant size dimorphism. Dimorphisms in dragonfishes and lanternfishes primarily involve the relative enlargement of particular photophores in the males. A sexual role is assumed, but the morphological differences are often small. Most male ponyfishes have enlarged light organs; behavioural observations of free-swimming animals have clearly demonstrated that the males use them to generate bioluminescent sexual signals.

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Janicke, Tim, and Edward H. Morrow. "Operational sex ratio predicts the opportunity and direction of sexual selection across animals." Ecology Letters 21, no. 3 (January 16, 2018): 384–91. http://dx.doi.org/10.1111/ele.12907.

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Clutton-Brock, Tim. "Reproductive competition and sexual selection." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1729 (July 31, 2017): 20160310. http://dx.doi.org/10.1098/rstb.2016.0310.

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This paper traces the development of our understanding of the development of different approaches to estimating the strength of reproductive competition and sexual selection in the two sexes, based on measures of the operational sex ratio, the opportunity for sexual selection and contrasts in selection gradients between the sexes. It argues that different approaches provide complementary insights into the causes of sex differences in reproductive competition, the operation of sexual selection and the evolution of secondary sexual characters and that improvements in our understanding of the evolution of secondary sexual characters will require a more comprehensive understanding of the ways in which social and ecological conditions modify reproductive competition and development in females and males. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

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Cassini, Marcelo H. "Sexual size dimorphism and sexual selection in artiodactyls." Behavioral Ecology 31, no. 3 (March 29, 2020): 792–97. http://dx.doi.org/10.1093/beheco/araa017.

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Abstract Sexual size dimorphism is biased toward males in most mammalian species. The most common explanation is precopulatory intramale sexual selection. Large males win fights and mate more frequently. In artiodactyls, previous tests of this hypothesis consisted of interspecific correlations of sexual dimorphism with group size as a surrogate for the intensity of sexual selection (Is). However, group size is not a proper measure of sexual selection for several reasons as is largely recognized in other mammalian taxa. I conducted an interspecific test on the role of sexual selection in the evolution of sexual dimorphism using the variance in genetic paternity as a proxy for the Is. I reviewed the literature and found 17 studies that allowed estimating Is= V/(W2), where V and W are the variance and mean number of offspring per male, respectively. A phylogenetic generalized least squares analysis indicated that dimorphism (Wm/Wf) showed a significant positive regression with the intensity of sexual selection but not group size (multiple r2= 0.40; F3,17= 12.78, P = 0.002). This result suggests that sexual selection may have played a role in the evolution of sexual size dimorphism in Artiodactyla. An alternative hypothesis based on natural selection is discussed.

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Pyatnitskiy, N. Yu. "The doctrine of instincts and emotions in Charles darwin’s monograph «The descent of Man and Sexual Selection» as a basis of contemporary evolutional psychiatry and psychology." Psychiatry and psychopharmacotherapy 26, no. 2 (April 2024): 28–34. http://dx.doi.org/10.62202/2075-1761-2024-26-2-28-34.

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The article presents an analysis of the doctrine of instincts and emotions in Charles Darwin's fundamental work “The Descent of Man and Sexual Selection” from the point of view of its significance for contemporary evolutionary psychiatry and psychology. Darwin believed that man has common instincts with animals (sexual love, self-preservation, maternal, social, etc.) and emotions (fear, suspicion, feelings of competition, sympathy; pleasure, suffering, vindictiveness, good nature, moral sense, etc.), and to substantiate this, he made systematic comparisons of the behavior of humans and animals of different species, arguing that with all the diversity of instincts, their number in humans is less than in animals. Darwin paid particular attention to animals that “gained from living” in close-knit communities. At the same time, Darwin did not see a fundamental difference between the mental abilities of humans and lower animals, noting that some species of higher animals also possess self-awareness. Most of the instincts, according to Darwin, were acquired by both people and animals through natural selection, operating by the “trial method,” because of that errors are often found in instincts. Darwin also believed that animals could suffer from insanity, but to a lesser extent than humans. In «The Descent of Man», Darwin outlined the problem of the existence of altruism and a “high level of morality”, which is relevant for contemporary evolutionary psychiatry and psychology. Аt the individual level of natural selection these traits may not bring any benefit to their owner (and even lead to his death as a result of self-sacrifice), and, it would seem, lead to the disappearance of owners of such qualities in subsequent generations.

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Journal articles on the topic 'Sexual selection in animals'

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