scholarly journals Multiple sexual selection pressures drive the rapid evolution of complex morphology in a male secondary genital structure

2015 ◽  
Vol 5 (19) ◽  
pp. 4437-4450 ◽  
Author(s):  
Stephen R. Frazee ◽  
John P. Masly
Keyword(s):  
Sexual Selection ◽  
Rapid Evolution ◽  
Selection Pressures ◽  
Complex Morphology ◽  
Genital Structure

Male terminalia morphology of sixteen species of the Drosophila saltans group Sturtevant (Diptera, Drosophilidae)

Zootaxa ◽  
2021 ◽  
Vol 5061 (3) ◽  
pp. 523-544
Author(s):  
BRUNA EMILIA ROMAN ◽  
LILIAN MADI-RAVAZZI
Keyword(s):  
Sexual Selection ◽  
Sibling Species ◽  
Potential Role ◽  
Rapid Evolution ◽  
Variable Structure ◽  
Diagnostic Feature ◽  
Internal Fertilization ◽  
Saltans Group

Male terminalia in insects with internal fertilization evolve more rapidly than other structures. The aedeagus is the most variable structure, making it a valuable diagnostic feature to distinguish species. The saltans group Sturtevant of Drosophila Fallén contains sibling species, that can be distinguished by their aedeagi. Here, we revised and illustrated the morphology of the male terminalia of the following species: Drosophila prosaltans Duda, 1927; D. saltans Sturtevant, 1916; D. lusaltans Magalhães, 1962; D. austrosaltans Spassky, 1957; D. septentriosaltans Magalhães, 1962; D. nigrosaltans Magalhães, 1962; D. pseudosaltans Magalhães, 1956; D. sturtevanti Duda, 1927; D. lehrmanae Madi-Ravazzi et al., 2021; D. dacunhai Mourão & Bicudo, 1967; D. milleri Magalhães, 1962; D. parasaltans Magalhães, 1956; D. emarginata Sturtevant, 1942; D. neoelliptica Pavan & Magalhães in Pavan, 1950; D. neosaltans Pavan & Magalhães in Pavan, 1950 and D. neocordata Magalhães, 1956. We found that phallic structures (e.g., the aedeagus) evolve more rapidly than periphallic structures (e.g., epandrium), being completely different among the subgroups and within them. This rapid evolution may be due to the action of sexual selection or to the potential role of those structures in speciation.  

Rapid evolution by sexual selection in a wild, invasive mammal

Evolution ◽  
2020 ◽  
Vol 74 (4) ◽  
pp. 740-748
Author(s):  
M. Aaron Owen ◽  
David C. Lahti
Keyword(s):  
Sexual Selection ◽  
Rapid Evolution

Behavioural and genetic analyses of mate choice and reproductive success in two Chinook salmon populations

2013 ◽  
Vol 70 (2) ◽  
pp. 263-270 ◽  
Author(s):  
Melissa L. Evans ◽  
Bryan D. Neff ◽  
Daniel D. Heath
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Reproductive Success ◽  
Mate Choice ◽  
Mhc Class Ii ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Mating Behaviour ◽  
Selection Pressures ◽  
Evolutionary Force

Sexual selection is recognized as an important evolutionary force in salmon. However, relatively little is known about variation in sexual selection pressures across salmon populations or the potential role of natural selection as a driver of adaptive mating patterns. Here, we examine mating behaviour and correlates of reproductive success in Chinook salmon (Oncorhynchus tshawytscha) from the Quinsam and Little Qualicum rivers in British Columbia, Canada — two populations for which we have previously found evidence of natural selection operating on major histocompatibility complex (MHC) genes. In both populations, males courted females and exhibited dominance behaviour towards other males, and the frequency of each behaviour was positively associated with reproductive success. Males were more aggressive towards females with whom they would produce offspring of low or high MHC class II diversity, and the offspring of males from the Quinsam River exhibited higher diversity at the MHC class I than expected. We discuss our results in relation to local natural selection pressures on the MHC and the potential for MHC-dependent mate choice.

The evolution of bird coloration

1979 ◽  
Vol 287 (1018) ◽  
pp. 63-130 ◽  
Keyword(s):  
Sexual Selection ◽  
Predation Risk ◽  
Multiple Regression ◽  
Reproductive Biology ◽  
Female Choice ◽  
Sex Recognition ◽  
Selection Pressures ◽  
Advantages And Disadvantages ◽  
Selective Pressures ◽  
Bird Coloration

The aims in this paper are first to review theories of the evolution of bird coloration and, in some cases, partly revise and extend them, secondly to analyse the coloration of all the birds of a given geographical region using multiple regression, and thirdly on the basis of this analysis to evaluate the various theories. Theories . There have been many discussions of the selective forces acting on the coloration of birds and we review the major proposals in some detail. The earliest suggestion (Darwin 1871) was that the bright coloration of many male birds originated through sexual selection by female choice of the most exotic variants in male plumage. A conflicting view (Hingston 1933) is that brightness has an intimidatory effect on opponents, and that bright male coloration arose through sexual selection but largely due to its advantages against other males in disputes concerning mating access to females. Bird coloration has also been considered in terms of predation (see, for example, Cott 1964 a ). Some birds with bright plumage patterns are known to be unpalatable compared to cryptic species, and certain other patterns have been interpreted as adaptations to confuse predators. Bright colours may commonly be favoured when an individual is anyhow obvious (e.g. through activity) and where it represents an 'unprofitable’ prey for a predator. This interpretation may be particularly relevant to lekking among polygamous males. A special case of unprofitable prey may be ‘perception advertisement’, where an animal signals (by flash patterns or alarm calls) that it has seen a predator (or opponent). It is also possible that bright coloration may serve to deflect predators away from the nest site; this requires in many ways conditions opposite to those for the unprofitable prey solution. Finally, bird colorations can act as a variety of social signals other than threat. Analysis . The coloration of the 516 species of birds that breed and/ or winter in the Western Palaearctic was analysed by multiple regression. Seven regions of a bird’s body plus two areas of flash coloration were recognized and scored for colour on a cryptic/conspicuous scale. Five different age/sex/season categories were recognized and scored separately for each species. These dependent variables were each analysed with respect to 17 independent variables that reflect different aspects of the reproductive biology and ecology of the birds. The advantages and disadvantages of multiple regression as an analytical technique are discussed. Results . The analysis identifies associations between the reproductive biology and ecology of the birds and the coloration of the different regions of the body of the different age/sex/season classes. Apparent exceptions to these associations are also identified and discussed. A relatively large proportion of the associations made sense in terms of the theories presented and usually there was a strong implication that for any specific association one theory was more relevant than any of the others. The results indicate that by far the most potent selective pressures to have shaped bird coloration are those related to predation risk. A number of the theories make use of predation risk, each in a different way, and for most of them some support can be gained for their involvement in the evolution of bird coloration. Of all the theories, however, it is the unprofitable prey model that seems to account for the major part of the variation in bird coloration. By contrast, no clear evidence for the involvement of sexual selection in the evolution of bird coloration could be found. Indeed, many associations, such as that between sexual dimorphism and polygamy, were more readily explicable in terms of selection pressures due to predation risk than of sexual pressures. The suggestion that bird coloration is shaped by predation rather than by sexual selection in no way prevents the coloration, as it evolves, being incorporated within the species and sex recognition system. Conclusions . It is concluded that bird coloration has evolved almost entirely in response to predation-based selective pressures. Although plumage and coloration are involved in species and sex recognition systems, they have not evolved in response to sexual selection pressures. In species that are sexually dimorphic, the male is not brightly coloured as a result of female choice or male: male competition but because he represents a less profitable prey to a predator than the females and juveniles. We predict that brightly coloured birds will most often be found to suffer less from predation than will comparable more cryptic birds (though one of the predation-risk theories does allow the converse to be true).

scholarly journals tartan underlies the evolution of male Drosophila genital morphology

2018 ◽  
Author(s):  
Joanna F. D. Hagen ◽  
Cláudia C. Mendes ◽  
Amber Blogg ◽  
Alex Payne ◽  
Kentaro M. Tanaka ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Rapid Evolution ◽  
Organ Size ◽  
Phenotypic Change ◽  
Genital Organ ◽  
Phenotypic Differences ◽  
Bristle Number ◽  
Evolutionary Changes ◽  
Drosophila Mauritiana ◽  
Male Genital

AbstractMale genital structures are among the most rapidly evolving morphological traits and are often the only features that can distinguish closely related species. This process is thought to be driven by sexual selection and may reinforce species separation. However, while the genetic basis of many phenotypic differences have been identified, we still lack knowledge about the genes underlying evolutionary differences in male genital organs and organ size more generally. The claspers (surstyli) are periphallic structures that play an important role in copulation in insects. Here we show that natural variation in clasper size and bristle number between Drosophila mauritiana and D. simulans is caused by evolutionary changes in tartan (trn), which encodes a transmembrane leucine-rich repeat domain protein that mediates cell-cell interactions and affinity differences. There are no fixed amino acid differences in trn between D. mauritiana and D. simulans but differences in the expression of this gene in developing genitalia suggest cis-regulatory changes in trn underlie the evolution of clasper morphology in these species. Finally, analysis of reciprocal hemizyotes that are genetically identical, except for which species the functional allele of trn is from, determined that the trn allele of D. mauritiana specifies larger claspers with more bristles than the allele of D. simulans. Therefore we have identified the first gene underlying evolutionary change in the size of a male genital organ, which will help to better understand the rapid diversification of these structures and the regulation and evolution of organ size more broadly.Significance StatementThe morphology of male genital organs evolves rapidly driven by sexual selection. However, little is known about the genes underlying genitalia differences between species. Identifying these genes is key to understanding how sexual selection acts on development to produce rapid phenotypic change. We have found that the gene tartan underlies differences between male Drosophila mauritiana and D. simulans in the size and bristle number of the claspers - genital projections that grasp the female during copulation. Moreover, since tartan encodes a protein that is involved in cell affinity, this may represent a new developmental mechanism for morphological change. Therefore, our study provides new insights into genetic and developmental bases for the rapid evolution of male genitalia and organ size more generally.

Relative Cerebellum Size Is Not Sexually Dimorphic across Primates

2020 ◽  
Vol 95 (2) ◽  
pp. 93-101
Author(s):  
Alex R. DeCasien ◽  
James P. Higham
Keyword(s):  
Sex Differences ◽  
Sexual Selection ◽  
Sex Difference ◽  
Cognitive Abilities ◽  
Relative Size ◽  
Brain Evolution ◽  
Primate Species ◽  
Published Data ◽  
Heterogeneous Structure ◽  
Selection Pressures

Background/Aims: Substantive sex differences in behavior and cognition are found in humans and other primates. However, potential sex differences in primate neuroanatomy remain largely unexplored. Here, we investigate sex differences in the relative size of the cerebellum, a region that has played a major role in primate brain evolution and that has been associated with cognitive abilities that may be subject to sexual selection in primates. Methods: We compiled individual volumetric and sex data from published data sources and used MCMC generalized linear mixed models to test for sex effects in relative cerebellar volume while controlling for phylogenetic relationships between species. Given that the cerebellum is a functionally heterogeneous structure involved in multiple complex cognitive processes that may be under selection in males or females within certain species, and that sexual selection pressures vary so greatly across primate species, we predicted there would be no sex difference in the relative size of the cerebellum across primates. Results: Our results support our prediction, suggesting there is no consistent sex difference in relative cerebellum size. Conclusion: This work suggests that the potential for sex differences in relative cerebellum size has been subject to either developmental constraint or lack of consistent selection pressures, and highlights the need for more individual-level primate neuroanatomical data to facilitate intra- and inter-specific study of brain sexual dimorphism.

Urban Sexual Selection

2020 ◽  
pp. 234-252
Author(s):  
Tuul Sepp ◽  
Kevin J. McGraw ◽  
Mathieu Giraudeau
Keyword(s):  
Sexual Selection ◽  
Urban Environments ◽  
Wild Animal ◽  
Selection Pressures ◽  
Sexually Selected Traits ◽  
Chemical Signalling ◽  
Animal Populations ◽  
Challenges And Opportunities ◽  
Microevolutionary Change ◽  
Selected Traits

Human-modified habitats can present both challenges and opportunities for wild animals. Changes in the environment caused by urbanization can affect who survives and reproduces in wild animal populations. Accordingly, we can expect that changes in sexual selection pressures may occur in response to urbanization. Changes in sexually selected traits like bird song and colouration have been one of the main thrusts of urban ecology in recent decades. However, studies to date have focused on describing changes in sexual phenotypes in response to urban environmental change, and knowledge about genetic/microevolutionary change is lacking. Also, while some signalling modalities have been well studied and linked to human activities (e.g., changes in auditory signals in response to anthropogenic noise), others have received comparatively less attention in this context (e.g., effects of air pollution on chemical signalling). In addition, the focus has been mainly on the signal sender, instead of the signal receiver, thereby missing an important side of sexual selection. This chapter reviews the evidence that sexual selection pressures and sexually selected traits have been impacted by urban environments, with attention to the potential for rapid adaptive and plastic shifts in traits of signallers and receivers. It explores the possibilities that urbanization causes evolutionary change and speciation in wild animal populations through sexual selection. Finally, it provides new ideas for future studies to explore these questions and especially the evolution of female preferences in urban environments.

scholarly journals Lek-Like Mating System of the Monogamous Blue-Black Grassquit

The Auk ◽  
2001 ◽  
Vol 118 (2) ◽  
pp. 404-411 ◽  
Author(s):  
Juliana B. Almeida ◽  
Regina H. Macedo
Keyword(s):  
Sexual Selection ◽  
Mating System ◽  
Vegetation Structure ◽  
Selection Pressures ◽  
Ideal Candidate ◽  
Lek Mating

Abstract In this study, we investigated the role of display and mating system of the little known Neotropical Blue-black Grassquit (Volatinia jacarina). Males form aggregations and execute a highly conspicuous display, resembling traditional leks. Number of displaying males declined throughout the study period, though displaying intensity during the season showed no variation. Individual males had significantly different displaying rates and also defended territories of very different sizes, ranging from 13.0 to 72.5 m2, but we found no association between territory sizes and the average displaying rates of the resident males. There also is no association between displaying rates of males and size and vegetation structure of their territories. Four of seven nests were found within male territories and observations indicated that both sexes invest equally in caring for nestlings. Results suggest that the Blue-black Grassquit does not fit into the traditional lek mating system, contrary to what has been proposed in the scarce literature available. However, it is clear that these apparently monogamous birds behave like a lekking species. We speculate about the possibility that aggregation of nesting territories in this species may be due to sexual selection pressures, and suggest that the Blue-black Grassquit may be an ideal candidate to test Wagner's (1997) hidden-lek hypothesis.

scholarly journals Evolution of sexual cooperation from sexual conflict

2019 ◽  
Vol 116 (46) ◽  
pp. 23225-23231 ◽  
Author(s):  
Maria R. Servedio ◽  
John M. Powers ◽  
Russell Lande ◽  
Trevor D. Price
Keyword(s):  
Sexual Selection ◽  
Sexual Conflict ◽  
Population Genetic ◽  
Genetic Model ◽  
Pair Formation ◽  
Selection Pressures ◽  
Quantitative Genetic ◽  
Pair Bonds ◽  
Quantitative Genetic Model ◽  
Female Investment

In many species that form pair bonds, males display to their mate after pair formation. These displays elevate the female’s investment into the brood. This is a form of cooperation because without the display, female investment is reduced to levels that are suboptimal for both sexes. The presence of such displays is paradoxical as in their absence the male should be able to invest extra resources directly into offspring, to the benefit of both sexes. We consider that the origin of these displays lies in the exploitation of preexisting perceptual biases which increase female investment beyond that which is optimal for her, initially resulting in a sexual conflict. We use a combined population genetic and quantitative genetic model to show how this conflict becomes resolved into sexual cooperation. A cooperative outcome is most likely when perceptual biases are under selection pressures in other contexts (e.g., detection of predators, prey, or conspecifics), but this is not required. Cooperation between pair members can regularly evolve even when this provides no net advantage to the pair and when the display itself reduces a male’s contributions to raising the brood. The findings account for many interactions between the sexes that have been difficult to explain in the context of sexual selection.

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