Natural selection reverses the exaggeration of a male sexually selected trait, which increases female fitness

AbstractTheory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to date, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we used experimental evolution of replicate populations of broad-horned flour-beetles to test for evolutionary effects of sex-specific predation on an exaggerated sexually selected male trait, while also testing for effects on female lifetime reproductive success. We found that populations subjected to male-specific predation evolved smaller sexually selected traits and this indirectly increased female fitness, seemingly through intersexual genetic correlations we documented. Predation solely on females had no effects. Our findings support fundamental theory, but also reveal novel outcomes when natural selection targets sex-limited sexually selected characters.

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Natural selection increases female fitness by reversing the exaggeration of a male sexually selected trait

Nature Communications ◽

10.1038/s41467-021-23804-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kensuke Okada ◽

Masako Katsuki ◽

Manmohan D. Sharma ◽

Katsuya Kiyose ◽

Tomokazu Seko ◽

...

Keyword(s):

Sexual Selection ◽

Natural Selection ◽

Experimental Evolution ◽

Genetic Correlations ◽

Lifetime Reproductive Success ◽

Fundamental Theory ◽

Female Fitness ◽

Male Trait ◽

Flour Beetles ◽

Male Specific

AbstractTheory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to our knowledge, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we use experimental evolution of replicate populations of broad-horned flour beetles to test for effects of sex-specific predation on an exaggerated sexually selected male trait (the mandibles), while also testing for effects on female lifetime reproductive success. We find that populations subjected to male-specific predation evolve smaller sexually selected mandibles and this indirectly increases female fitness, seemingly through intersexual genetic correlations we document. Predation solely on females has no effects. Our findings support fundamental theory, but also reveal unforseen outcomes—the indirect effect on females—when natural selection targets sex-limited sexually selected characters.

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Preferential Sex Linkage of Sexually Selected Genes: Evidence and a New Explanation

The Speciation of Modern Homo Sapiens ◽

10.5871/bacad/9780197263112.003.0014 ◽

2004 ◽

Author(s):

Klaus Reinhold

Keyword(s):

Natural Selection ◽

X Chromosome ◽

Female Choice ◽

Sex Linkage ◽

Fluctuating Selection ◽

X Linkage ◽

Sexually Selected Traits ◽

Selected Traits

This chapter discusses evidence and theory on sex chromosomal linkage of sexually selected traits that may be the key to a functional separation of sexual and natural selection. It reviews the evidence showing that the X chromosome has a disproportional share concerning the inheritance of sexually selected traits in animals with heterogametic males, and suggests a new explanation that relates this X bias with female choice of heterozygotic males. With numeric simulations, it shows that female choice of heterozygotic males is usually disadvantageous. Because this disadvantage cannot occur when females prefer X-linked male traits, preferential X linkage of sexually selected traits can be expected. As an alternative to fluctuating selection on sex-limited traits, the disadvantage of heterozygotic choice may thus explain the X bias observed for sexually selected traits.

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Multimodal weighting differences by bats and their prey: probing natural selection pressures on sexually selected traits

Animal Behaviour ◽

10.1016/j.anbehav.2017.10.011 ◽

2017 ◽

Vol 134 ◽

pp. 99-102 ◽

Cited By ~ 7

Author(s):

D.G.E. Gomes ◽

W. Halfwerk ◽

R.C. Taylor ◽

M.J. Ryan ◽

R.A. Page

Keyword(s):

Natural Selection ◽

Selection Pressures ◽

Sexually Selected Traits ◽

Selected Traits

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Developmental costs of male sexual traits in the water strider Rheumatobates rileyi

Canadian Journal of Zoology ◽

10.1139/z99-058 ◽

1999 ◽

Vol 77 (6) ◽

pp. 917-922 ◽

Cited By ~ 12

Author(s):

Kathleen P Westlake ◽

Locke Rowe

Keyword(s):

Natural Selection ◽

Meta Analysis ◽

Development Rate ◽

Fourth Instar ◽

Water Strider ◽

The Third ◽

Intermolt Period ◽

Sexually Selected Traits ◽

Sexual Traits ◽

Selected Traits

Natural selection is thought to impose costs on sexually selected traits and thereby constrain their evolutionary modification. Where sexually selected traits involve increases in size or structural elaboration, development of the traits may be costly. Males of some species in the water strider genus Rheumatobates have dramatically elaborated antennae and legs. In a pair of experiments on Rheumatobates rileyi, we tested the hypothesis that in males, the development rate is decreased and mortality increased relative to unelaborated females during the final instar, when these traits were substantially developed. In the first experiment, we reared individual larvae through to adult that were brought into the laboratory during the third, fourth, and fifth (final) instars. The development rate was reduced and the mortality increased during the final intermolt period in males relative to females. The effect on development rate was highly significant, but the effect on mortality was not. Notably, there was no effect of sex on the duration of the fourth instar, when male modifications are not expressed. In a second experiment, 4 potentially cannibalistic adults were included with fifth-instar larvae. We found no effect of potential cannibals on either development rate or mortality of instars. However, as in the first experiment, the development rate was significantly reduced in males relative to females. Mortality of males was also higher than that of females, although this effect was not significant. Meta-analysis of all our mortality results indicate that mortality of developing fifth-instars was higher in males than in females. Our results are consistent with the hypothesis that development of elaborate sexual traits in male R. rileyi is costly.

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Genomic analysis reveals a polygenic architecture of antler morphology in wild red deer (Cervus elaphus)

10.1101/2021.04.16.440189 ◽

2021 ◽

Author(s):

Lucy Peters ◽

Jisca Huisman ◽

Loeske E.B. Kruuk ◽

Josephine M. Pemberton ◽

Susan E. Johnston

Keyword(s):

Genetic Variation ◽

Cervus Elaphus ◽

Genetic Architecture ◽

Empirical Bayes ◽

Red Deer ◽

Genetic Correlations ◽

Rapid Evolution ◽

Genomic Analysis ◽

Sexually Selected Traits ◽

Selected Traits

AbstractSexually-selected traits show large variation and rapid evolution across the animal kingdom, yet genetic variation often persists within populations despite apparent directional selection. A key step in solving this long-standing paradox is to determine the genetic architecture of sexually-selected traits to understand evolutionary drivers and constraints at the genomic level. Antlers are a form of sexual weaponry in male red deer. On the island of Rum, Scotland, males with larger antlers have increased breeding success, yet there has been no response to selection observed at the genetic level. To better understand the underlying mechanisms of this observation, we investigate the genetic architecture of ten antler traits and their principle components using genomic data from >38,000 SNPs. We estimate the heritabilities and genetic correlations of the antler traits using a genomic relatedness approach. We then use genome-wide association and haplotype-based regional heritability to identify regions of the genome underlying antler morphology, and an Empirical Bayes approach to estimate the underlying distributions of allele effect sizes. We show that antler morphology is heritable with a polygenic architecture, highly repeatable over an individual’s lifetime, and that almost all aspects are positively genetically correlated with some loci identified as having pleiotropic effects. Our findings suggest that a large mutational target and pleiotropy with traits sharing similar complex polygenic architectures are likely to contribute to the maintenance of genetic variation in antler morphology in this population.

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Pathogen dependent phenotypic but no genetic correlation between sexual activity and 3 immunity in male Drosophila melanogaster subjected to differential sexual selection

10.1101/144311 ◽

2017 ◽

Author(s):

Zeeshan Ali Syed ◽

Vanika Gupta ◽

Manas Arun Samant ◽

Aatashi Dhiman ◽

Nagaraj Guru Prasad

Keyword(s):

Drosophila Melanogaster ◽

Sexual Selection ◽

Experimental Evolution ◽

Post Infection ◽

Pathogenic Bacteria ◽

Limited Resources ◽

Trade Off ◽

Sexually Selected Traits ◽

Selected Traits ◽

Positive Correlations

AbstractThe theory of trade-off suggest that limited resources should lead to trade-off in resource intensive traits such as immunity related and sexually selected traits in males. Alternatively, sexual exaggerations can also act as an honest indicator of underlying immunocompetence, leading to positive correlations between these traits. Several studies have addressed this question using experimental evolution. However, they have rarely used ecologically relevant pathogens and fitness measurement (e.g., measuring post-infection survivorship) to find correlations between sexual selection and immunity. Here we attempt to address this caveat by evolving populations of Drosophila melanogaster under differential sexual selection. After more than hundred generations, we infected virgin and mated males from each population with three pathogenic bacteria: Pseudomonas entomophila (Pe), Staphylococcus succinus (Ss) and Providentia rettgeri (Pr). Fitness was measured as either post-infection survivorship (Pe and Ss) or bacterial clearance ability (Pr). Contrary to expectations, sexual selection had no evolutionary effect on male fitness against any of the pathogens. Moreover, mating had a beneficial effect against Pe and Pr, but no effect against Ss, suggesting pathogen specific phenotypic correlations between mating and immunity. Following these results, we discuss the significance of using ecologically relevant pathogens and quantifying host fitness while studying sexual selection-immunity correlations.

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