scholarly journals With our powers combined: integrating behavioral and genetic data to estimate mating success and sexual selection

2017 ◽  
Author(s):  
Zoé Gauthey ◽  
Cédric Tentelier ◽  
Olivier Lepais ◽  
Arturo Elosegi ◽  
Laura Royer ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Reproductive Success ◽  
Mating Success ◽  
Genetic Data ◽  
Male Body ◽  
Gamete Release ◽  
Sexual Interaction ◽  
Reproductive Process ◽  
Behavioral Observations

AbstractThe analysis of sexual selection classically relies on the regression of individual phenotypes against the marginal sums of a males × females matrix of pairwise reproductive success, assessed by genetic parentage analysis. When the matrix is binarized, the marginal sums give the individual mating success. Because such analysis treats male and female mating/reproductive success independently, it ignores that the success of a male × female sexual interaction can be attributable to the phenotype of both individuals. Also, because it is based on genetic data only, it is oblivious to costly yet unproductive matings, which may be documented by behavioral observations. To solve these problems, we propose a statistical model which combines matrices of offspring numbers and behavioral observations. It models reproduction on each mating occasion of a mating season as three stochastic and interdependent pairwise processes, each potentially affected by the phenotype of both individuals and by random individual effect: encounter (Bernoulli), concomitant gamete emission (Bernoulli), and offspring production (Poisson). Applied to data from a mating experiment on brown trout, the model yielded different results from the classical regression analysis, with only a limited effect of male body size on the probability of gamete release and a negative effect of female body size on the probability of encounter and gamete release. Because the general structure of the model can be adapted to other partitioning of the reproductive process, it can be used for a variety of biological systems where behavioral and genetic data are available.

scholarly journals Disruptive sexual selection on male body size in the polyphenic black scavenger fly Sepsis thoracica

2018 ◽  
Vol 29 (3) ◽  
pp. 769-777 ◽  
Author(s):  
Juan Pablo Busso ◽  
Wolf U Blanckenhorn
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Reproductive Success ◽  
Mating Success ◽  
Directional Selection ◽  
Disruptive Selection ◽  
Simultaneous Occurrence ◽  
Male Body ◽  
Male Body Size ◽  
Starting Point

Abstract Sexual selection has 2 main components, female preference and male–male competition, which can lead males to adopt alternative reproductive tactics to optimize their reproductive success. Two traits that significantly influence reproductive success are body size and coloration, as they can facilitate access to females through male contests or as female attractors. We investigated whether, and if so which mechanism of sexual selection contributes to the maintenance, and possibly even the establishment, of 2 almost discrete male morphs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae): small and black, or large and amber. We performed 2 complementary laboratory experiments to evaluate the mating success of the different male morphs and the behaviors (of both males and females) presumably mediating their mating success. We found evidence for intraspecific disruptive sexual selection on male body size that is mediated by male–male interactions, and significant positive directional selection on body size that interacted with (directional) selection on coloration, likely contributing to the origin and/or maintenance of the threshold relationship between the 2 traits in this species. The simultaneous occurrence of disruptive selection and polyphenism in S. thoracica supports the role of sexual selection in the intraspecific diversification of coupled traits (here body size and coloration), which could be a speciation starting point.

scholarly journals Sexual selection on size and shape in Japanese beetles (Popillia japonica)

2020 ◽  
Vol 31 (4) ◽  
pp. 1073-1083 ◽  
Author(s):  
Clint D Kelly
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Mating Success ◽  
Insect Pest ◽  
Popillia Japonica ◽  
Female Size ◽  
Male Body ◽  
Japanese Beetle ◽  
Size Dimorphism ◽  
Selection For

Abstract The mobility hypothesis argues that species in which males compete for mates in scrambles often exhibit female-biased size dimorphism because smaller male body size should increase male mobility and success in searching for mates. Sexual dimorphism can be further exaggerated if fecundity or sexual selection concurrently selects for larger female size. Scramble competition can select for trait characteristics that optimize locomotion; for example, long and slender wings should be favored if aerial speed is important to mating success. I tested these predictions in the scrambling Japanese beetle (Popillia japonica), a female-biased size dimorphic insect pest that is invasive to North America. Multivariate selection analyses support the prediction that smaller body size and larger wings in males benefit their mating success. My analyses also revealed significant selection for larger wings in females but, contrary to prediction, direct sexual selection favors smaller body size in females. These results support the mobility hypothesis and partially explain the evolution of female-biased size dimorphism in this species. Sexual selection favored rounder bodies in females and more tapered bodies in males, whereas, in both sexes, the effect of wing shape appears less important to fitness than wing size.

Size does not matter for male Marbled Salamanders (Ambystoma opacum)

2015 ◽  
Vol 93 (10) ◽  
pp. 735-740
Author(s):  
D.A. Croshaw ◽  
J.H.K. Pechmann
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Reproductive Success ◽  
Large Male ◽  
Male Mating ◽  
Ambystoma Opacum ◽  
Positive Assortative Mating ◽  
Important Trait ◽  
Breeding Groups ◽  
Gravid Females

Understanding the phenotypic attributes that contribute to variance in mating and reproductive success is crucial in the study of evolution by sexual selection. In many animals, body size is an important trait because larger individuals enjoy greater fitness due to the ability to secure more mates and produce more offspring. Among males, this outcome is largely mediated by greater success in competition with rival males and (or) advantages in attractiveness to females. Here we tested the hypothesis that large male Marbled Salamanders (Ambystoma opacum (Gravenhorst, 1807)) mate with more females and produce more offspring than small males. In experimental breeding groups, we included males chosen specifically to represent a range of sizes. After gravid females mated and nested freely, we collected egg clutches and genotyped all adults and samples of hatchlings with highly variable microsatellite markers to assign paternity. Size had little effect on male mating and reproductive success. Breeding males were not bigger than nonbreeding males, mates of polyandrous females were not smaller than those of monogamous females, and there was no evidence for positive assortative mating by size. Although body size did not matter for male Marbled Salamanders, we documented considerable fitness variation and discuss alternative traits that could be undergoing sexual selection.

Sexual size dimorphism in the American rubyspot: male body size predicts male competition and mating success

2007 ◽  
Vol 73 (6) ◽  
pp. 987-997 ◽  
Author(s):  
M.A. Serrano-Meneses ◽  
A. Córdoba-Aguilar ◽  
V. Méndez ◽  
S.J. Layen ◽  
T. Székely
Keyword(s):  
Body Size ◽  
Mating Success ◽  
Sexual Size Dimorphism ◽  
Male Competition ◽  
Male Body ◽  
Size Dimorphism ◽  
Male Body Size

The quantitative genetics of sexual selection in the dung fly Sepsis cynipsea

Behaviour ◽  
2004 ◽  
Vol 141 (3) ◽  
pp. 327-341 ◽  
Author(s):  
Wolf Blanckenhorn ◽  
Claudia Mühlhäuser
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Genetic Correlation ◽  
Quantitative Genetics ◽  
Sexual Conflict ◽  
Good Genes ◽  
Male Body ◽  
Selection Models ◽  
Sexually Selected Traits ◽  
Mating Cost

AbstractIn the common dung or black scavenger fly Sepsis cynipsea (Diptera: Sepsidae) several morphological and behavioural male and female traits interact during mating. Previous studies show that males attempt to mount females without courtship, females use vigorous shaking behaviour in response to male mounting, the duration of shaking is an indicator of both direct and indirect female choice and sexual conflict, and larger males enjoy a mating advantage. We conducted a quantitative genetic paternal half sib study to investigate the genetic underpinnings of these traits, notably body size (the preferred trait) and the associated female preference, and to assess the relative importance of various models generally proposed to account for the evolution of sexually selected traits. Several morphological traits and female shaking duration were heritable, thus meeting a key requirement of all sexual selection models. In contrast, two traits indicative of male persistence in mating were not. Male longevity was also heritable and negatively correlated with his mating effort, suggesting a mating cost. However, the crucial genetic correlation between male body size and female shaking duration, predicted to be negative by both 'good genes' and Fisherian models and positive by the sexual conflict (or chase-away) model, was zero. This could be because of low power, or because of constraints imposed by the genetic correlation structure. Based on our rsults we conclude that discriminating sexual selection models by sole means of quantitative genetics is difficult, if not impossible.

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