The causes and consequences of ornament variation in a natural population

2019 ◽  
Author(s):  
Annabel Ralph ◽  
Terry Burke ◽  
Shinichi Nakagawa ◽  
Alfredo Sánchez-Tójar ◽  
Julia Schroeder
Keyword(s):  
Sexual Selection ◽  
Evolutionary Biology ◽  
Natural Populations ◽  
Size Variation ◽  
Evolutionary Potential ◽  
House Sparrows ◽  
Sexually Selected Traits ◽  
Evolutionary Response ◽  
Significant Heritability ◽  
Selected Traits

The role of sexual selection in natural populations has long been the subject of debate in evolutionary biology. Ornaments are sexually selected traits, which means they should vary within a population, have a genetic basis, and be associated with fitness. Despite evidence of ornaments meeting these criteria, evolutionary responses to sexual selection are rare in nature. This study focuses on two ornaments in a population of house sparrows; the plumage badge has been well-studied but remains poorly understood and the mask has been largely neglected in the literature. Using quantitative genetic techniques, we estimate the heritability of both traits and test for age-dependency of the heritability estimates. We also estimate the strength and direction of any selection acting upon the traits. We found that both ornaments have low, significant heritability, which does not vary with age. Selection only occurs in a small number of years, although when it does it is positive in both ornaments. We also found that early social environment plays a role in badge size variation. The results of this study suggest that an evolutionary response in the ornaments of this population is unlikely, but we highlight the importance of long-term research to improve our understanding of evolution in natural populations. Studies like these will add to our understanding of sexual selection, the causes of trait variation and the evolutionary potential of traits, which could help us to predict how populations will evolve.

scholarly journals Mhc polymorphisms fail to explain the heritability of phytohaemagglutinin-induced skin swelling in a wild passerine

2009 ◽  
Vol 5 (6) ◽  
pp. 784-787 ◽  
Author(s):  
Camille Bonneaud ◽  
Janet S. Sinsheimer ◽  
Murielle Richard ◽  
Olivier Chastel ◽  
Gabriele Sorci
Keyword(s):  
Genetic Variation ◽  
Immune Responses ◽  
Environmental Effects ◽  
Natural Populations ◽  
Wild Populations ◽  
Genetic Determinants ◽  
House Sparrows ◽  
Additive Genetic Variation ◽  
Significant Heritability ◽  
Mhc Polymorphisms

Genetic estimates of the variability of immune responses are rarely examined in natural populations because of confounding environmental effects. As a result, and because of the difficulty of pinpointing the genetic determinants of immunity, no study has to our knowledge examined the contribution of specific genes to the heritability of an immune response in wild populations. We cross-fostered nestling house sparrows to disrupt the association between genetic and environmental effects and determine the heritability of the response to a classic immunological test, the phytohaemagglutinin (PHA)-induced skin swelling. We detected significant heritability estimates of the response to PHA, of body mass and tarsus length when nestlings were 5 and 10 days old. Variation at Mhc genes, however, did not explain a significant portion of the genetic variation of nestling swelling to PHA. Our results suggest that while PHA-induced swelling is influenced by the nest of origin, the importance of additive genetic variation relative to non-additive genetic variation and the genetic factors that influence the former in wild populations still need to be identified for this trait.

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 Sexually selected skin colour is heritable and related to fecundity in a non-human primate

2014 ◽  
Vol 281 (1794) ◽  
pp. 20141602 ◽  
Author(s):  
Constance Dubuc ◽  
Sandra Winters ◽  
William L. Allen ◽  
Lauren J. N. Brent ◽  
Julie Cascio ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Individual Variation ◽  
Balancing Selection ◽  
Rhesus Macaques ◽  
Reproductive Rate ◽  
Condition Dependence ◽  
Selection Gradients ◽  
Sexually Selected Traits ◽  
Skin Redness ◽  
Selected Traits

Sexual selection promotes the prevalence of heritable traits that increase an individual's reproductive rate. Despite theoretically strong directional selection, sexually selected traits can show inter-individual variation. Here, we investigate whether red skin ornamentation, a rare example of a male mammalian trait involved in mate attraction, influences fecundity and is heritable in rhesus macaques ( Macaca mulatta ), and explore the mechanisms that are involved in maintaining trait variation. Interestingly, the trait is expressed by and is attractive to both sexes. We collected facial images of 266 free-ranging individuals and modelled skin redness and darkness to rhesus macaque vision. We used 20 years of genetic parentage data to calculate selection gradients on the trait and perform heritability analyses. Results show that males who were both darkly coloured and high-ranking enjoyed higher fecundity. Female skin redness was positively linked to fecundity, although it remains unclear whether this influences male selectiveness. Heritability explained 10–15% of the variation in redness and darkness, and up to 30% for skin darkness when sexes are considered separately, suggesting sex-influenced inheritance. Our results suggest that inter-individual variation is maintained through condition-dependence, with an added effect of balancing selection on male skin darkness, providing rare evidence for a mammalian trait selected through inter-sexual selection.

scholarly journals Rapid courtship evolution in grouse (Tetraonidae): contrasting patterns of acceleration between the Eurasian and North American polygynous clades

2007 ◽  
Vol 274 (1613) ◽  
pp. 1079-1086 ◽  
Author(s):  
Allen Spaulding
Keyword(s):  
Sexual Selection ◽  
Mating Success ◽  
Male Mating ◽  
Sexually Dimorphic ◽  
Sexually Selected Traits ◽  
Species Pairs ◽  
Rapid Divergence ◽  
Nucleotide Divergence ◽  
Selected Traits ◽  
Dimorphic Species

Sexual selection is thought to be a powerful diversifying force, based on large ornamental differences between sexually dimorphic species. This assumes that unornamented phenotypes represent evolution without sexual selection. If sexual selection is more powerful than other forms of selection, then two effects would be: rapid divergence of sexually selected traits and a correlation between these divergence rates and variance in mating success in the ornamented sex. I tested for these effects in grouse (Tetraonidae). For three species pairs, within and among polygynous clades, male courtship characters had significantly greater divergence than other characters. This was most pronounced for two species in Tympanuchus . In the Eurasian polygynous clade, relative courtship divergence gradually increased with nucleotide divergence, suggesting a less dramatic acceleration. Increase in relative courtship divergence was associated with mating systems having higher variance in male mating success. These results suggest that sexual selection has accelerated courtship evolution among grouse, although the microevolutionary details appear to vary among clades.

scholarly journals Female preference for multi-modal courtship: multiple signals are important for male mating success in peacock spiders

2015 ◽  
Vol 282 (1820) ◽  
pp. 20152222 ◽  
Author(s):  
Madeline B. Girard ◽  
Damian O. Elias ◽  
Michael M. Kasumovic
Keyword(s):  
Sexual Selection ◽  
Mating Success ◽  
Female Preference ◽  
Male Mating ◽  
Sexually Dimorphic ◽  
Complex Signals ◽  
Sexually Selected Traits ◽  
Redundant Signal ◽  
Multiple Messages ◽  
Selected Traits

A long-standing goal for biologists has been to understand how female preferences operate in systems where males have evolved numerous sexually selected traits. Jumping spiders of the Maratus genus are exceptionally sexually dimorphic in appearance and signalling behaviour. Presumably, strong sexual selection by females has played an important role in the evolution of complex signals displayed by males of this group; however, this has not yet been demonstrated. In fact, despite apparent widespread examples of sexual selection in nature, empirical evidence is relatively sparse, especially for species employing multiple modalities for intersexual communication. In order to elucidate whether female preference can explain the evolution of multi-modal signalling traits, we ran a series of mating trials using Maratus volans . We used video recordings and laser vibrometry to characterize, quantify and examine which male courtship traits predict various metrics of mating success. We found evidence for strong sexual selection on males in this system, with success contingent upon a combination of visual and vibratory displays. Additionally, independently produced, yet correlated suites of multi-modal male signals are linked to other aspects of female peacock spider behaviour. Lastly, our data provide some support for both the redundant signal and multiple messages hypotheses for the evolution of multi-modal signalling.

scholarly journals Mating system and brain size in bats

2005 ◽  
Vol 273 (1587) ◽  
pp. 719-724 ◽  
Author(s):  
Scott Pitnick ◽  
Kate E Jones ◽  
Gerald S Wilkinson
Keyword(s):  
Sexual Selection ◽  
Mating System ◽  
Multiple Mating ◽  
Brain Size ◽  
Evolutionary Relationship ◽  
Brain Evolution ◽  
Correlated Evolution ◽  
Mate Fidelity ◽  
Sexually Selected Traits ◽  
Selected Traits

The contribution of sexual selection to brain evolution has been little investigated. Through comparative analyses of bats, we show that multiple mating by males, in the absence of multiple mating by females, has no evolutionary impact on relative brain dimension. In contrast, bat species with promiscuous females have relatively smaller brains than do species with females exhibiting mate fidelity. This pattern may be a consequence of the demonstrated negative evolutionary relationship between investment in testes and investment in brains, both metabolically expensive tissues. These results have implications for understanding the correlated evolution of brains, behaviour and extravagant sexually selected traits.

scholarly journals Intraspecific sperm competition genes enforce post-mating species barriers in Drosophila

2014 ◽  
Vol 281 (1797) ◽  
pp. 20142050 ◽  
Author(s):  
Dean M. Castillo ◽  
Leonie C. Moyle
Keyword(s):  
Sexual Selection ◽  
Reproductive Isolation ◽  
Sperm Competition ◽  
Competitive Ability ◽  
Sexual Isolation ◽  
Theoretical Models ◽  
Sexually Selected Traits ◽  
Genetic Mechanisms ◽  
Selected Traits ◽  
Additional Role

Sexual selection and sexual conflict are considered important drivers of speciation, based on both theoretical models and empirical correlations between sexually selected traits and diversification. However, whether reproductive isolation between species evolves directly as a consequence of intrapopulation sexual dynamics remains empirically unresolved, in part because knowledge of the genetic mechanisms (if any) connecting these processes is limited. Here, we provide evidence of a direct mechanistic link between intraspecies sexual selection and reproductive isolation. We examined genes with known roles in intraspecific sperm competition (ISC) in D. melanogaster and assayed their impact on conspecific sperm precedence (CSP). We found that two such genes ( Acp36DE and CG9997 ) contribute to both offensive sperm competition and CSP; null/knockdown lines both had lower competitive ability against D. melanogaster conspecifics and were no longer able to displace heterospecific D. simulans sperm in competitive matings. In comparison, Sex Peptide ( Acp70A )—another locus essential for ISC—does not contribute to CSP. These data indicate that two loci important for sperm competitive interactions have an additional role in similar interactions that enforce post-mating reproductive isolation between species, and show that sexual selection and sexual isolation can act on the same molecular targets in a gene-specific manner.

Geographical variation in the male intromittent organ of the Trinidadian guppy (Poecilia reticulata)

2000 ◽  
Vol 78 (9) ◽  
pp. 1674-1680 ◽  
Author(s):  
Clint D Kelly ◽  
Jean-Guy J Godin ◽  
Ghada Abdallah
Keyword(s):  
Phenotypic Variation ◽  
Poecilia Reticulata ◽  
Natural Populations ◽  
Fish Predation ◽  
Species Variation ◽  
Body Coloration ◽  
Sexually Selected Traits ◽  
Predation Intensity ◽  
Trinidadian Guppy ◽  
Selected Traits

Sexual selection may favour the evolution of elaborated genital traits in males, particularly when phenotypic variation in such traits results in corresponding variation in reproductive success among males in the population. Compared with insects, very little is known about the natural variation in any male genital trait, and its causes, in vertebrates. Here we report on variation in a male intromittent organ both within and between natural populations of a vertebrate, the Trinidadian guppy (Poecilia reticulata). Male guppies inseminate females using an intromittent organ called the gonopodium. We demonstrate that males from populations that have evolved under high fish-predation intensity have, on average, a relatively longer gonopodium than males originating from populations under low fish-predation intensity. Compared with body coloration, the gonopodium exhibited relatively low phenotypic variation, but nonetheless was within the range of known variation for sexually selected traits. The male gonopodium was positively allometric in general. To our knowledge, this is the first report of within-species variation in an intromittent organ and of a positive allometric relationship between male genitalia and body size in a vertebrate species. Our results suggest that the length of the male intromittent organ in the guppy is under selection, which varies geographically.

scholarly journals Evolutionary rates for multivariate traits: the role of selection and genetic variation

2014 ◽  
Vol 369 (1649) ◽  
pp. 20130252 ◽  
Author(s):  
William Pitchers ◽  
Jason B. Wolf ◽  
Tom Tregenza ◽  
John Hunt ◽  
Ian Dworkin
Keyword(s):  
Evolutionary Biology ◽  
Genetic Architecture ◽  
Genetic Variance ◽  
Evolutionary Rates ◽  
Phenotypic Traits ◽  
Sexually Selected Traits ◽  
Rates Of Evolution ◽  
Selected Traits ◽  
Multivariate Traits

A fundamental question in evolutionary biology is the relative importance of selection and genetic architecture in determining evolutionary rates. Adaptive evolution can be described by the multivariate breeders' equation ( ), which predicts evolutionary change for a suite of phenotypic traits ( ) as a product of directional selection acting on them ( β ) and the genetic variance–covariance matrix for those traits ( G ). Despite being empirically challenging to estimate, there are enough published estimates of G and β to allow for synthesis of general patterns across species. We use published estimates to test the hypotheses that there are systematic differences in the rate of evolution among trait types, and that these differences are, in part, due to genetic architecture. We find some evidence that sexually selected traits exhibit faster rates of evolution compared with life-history or morphological traits. This difference does not appear to be related to stronger selection on sexually selected traits. Using numerous proposed approaches to quantifying the shape, size and structure of G , we examine how these parameters relate to one another, and how they vary among taxonomic and trait groupings. Despite considerable variation, they do not explain the observed differences in evolutionary rates.

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