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 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.

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

Mating system, mate choice and parental care in a bark beetle

2017 ◽  
Vol 107 (5) ◽  
pp. 611-619 ◽  
Author(s):  
O. Baruch ◽  
Z. Mendel ◽  
I. Scharf ◽  
A. R Harari
Keyword(s):  
Body Size ◽  
Reproductive Success ◽  
Mate Choice ◽  
Parental Care ◽  
Mating System ◽  
Assortative Mating ◽  
Bark Beetle ◽  
Biparental Care ◽  
Male Body ◽  
Male Body Size

AbstractThe cypress bark beetle,Phloeosinus armatus, is a common element of the dying cypress tree system in East-Mediterranean countries. Adult beetles congregate for breeding on this ephemeral resource. We studied three traits that characterize this beetle's sexual behavior and linked them to its reproductive success: mating system, mate choice, and parental care. We found that the females are the ‘pioneering sex’, excavating the mating chamber. The average female is slightly larger than the male, and female and male body size is correlated, demonstrating size-assortative mating. The time it takes for a male to enter the mating chamber is positively correlated with female size and negatively correlated with its own size, which is perhaps responsible for this assortative mating. Males remain in the gallery during the period of oviposition, gradually leaving soon after the eggs hatch. The number of eggs laid and tunnel length are positively correlated with male body size. Finally, in the presence of both parents, more eggs are laid than when the female alone is present, demonstrating the important contribution of biparental care for reproductive success. We suggest that the interaction between a monogamous mating system, assortative mating, and biparental care contributes to reproductive success.

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.

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