scholarly journals Fluctuating selection strength and intense male competition underlie variation and exaggeration of a water strider’s male weapon

2018 ◽  
Author(s):  
William Toubiana ◽  
Abderrahman Khila
Keyword(s):  
Mating Behavior ◽  
Phenotypic Variation ◽  
Male Competition ◽  
Egg Laying ◽  
Leg Length ◽  
Fluctuating Selection ◽  
Sexually Selected Traits ◽  
Selected Traits ◽  
Gravid Females ◽  
The Impact

AbstractSexually selected traits can reach high degrees of expression and variation under directional selection. A growing number of studies suggest that such selection can vary in space, time and form within and between populations. However, the impact of these fluctuations on sexual trait expression is poorly understood. The water striderMicrovelia longipesdisplays a striking case of exaggeration and phenotypic variation where males display extreme differences in the size of their rear legs. To study the origin and maintenance of this exaggerated trait, we conducted comparative behavioral and morphometric experiments in a sample ofMicroveliaspecies. We uncovered differences both in the mating behavior and the degree of sexual dimorphism across these species. Interestingly,M. longipesevolved a specific mating behavior where males compete for egg-laying sites, consisting of small floating objects, to intercept and copulate with gravid females. Field observations revealed rapid fluctuation inM. longipeshabitat stability and the abundance of egg-laying sites. Through male-male competition assays, we demonstrated that male rear legs are used as weapons to dominate egg-laying sites and that intense competition is associated with the evolution of rear leg length exaggeration. Paternity tests using genetic markers demonstrated that small males could only fertilize about 5% of the eggs when egg-laying sites are limiting, whereas this proportion increased to about 20% when egg-laying sites become abundant. Furthermore, diet manipulation and artificial selection experiments also showed that the exaggerated leg length inM. longipesmales is influenced by both genetic and nutritional factors. Collectively, our results highlight how fluctuation in the strength of directional sexual selection, through changes in the intensity of male competition, can drive the exaggeration and phenotypic variation in this weapon trait.

scholarly journals Fluctuating selection strength and intense male competition underlie variation and exaggeration of a water strider's male weapon

2019 ◽  
Vol 286 (1901) ◽  
pp. 20182400 ◽  
Author(s):  
William Toubiana ◽  
Abderrahman Khila
Keyword(s):  
Phenotypic Variation ◽  
Mating Behaviour ◽  
Phenotypic Expression ◽  
Reaction Norm ◽  
Male Competition ◽  
Egg Laying ◽  
Leg Length ◽  
Fluctuating Selection ◽  
Sexually Selected Traits ◽  
The Impact

Sexually selected traits can reach high degrees of phenotypic expression and variation under directional selection. A growing number of studies suggest that such selection can vary in space, time and form within and between populations. However, the impact of these fluctuations on sexual trait evolution is poorly understood. In the water strider Microvelia longipes , males display striking trait exaggeration and phenotypic variation manifested as extreme differences in the rear leg length. To study the origin and maintenance of this exaggerated trait, we conducted comparative behavioural, morphometric and reaction norm experiments in a selection of Microvelia species. We uncovered differences both in the mating behaviour and the degree of sexual dimorphism across these species. Interestingly, M. longipes evolved a specific mating behaviour where males compete for egg-laying sites, consisting of small floating objects, to intercept and copulate with gravid females. Through male–male competition assays, we demonstrated that male rear legs are used as weapons to dominate egg-laying sites and that intense competition is associated with the evolution of rear leg length exaggeration. Field observations revealed rapid fluctuation in M. longipes habitat stability and the abundance of egg-laying sites. Paternity tests using genetic markers demonstrated that small males could only fertilize about 5% of the eggs when egg-laying sites are limiting, whereas this proportion increased to about 20% when egg-laying sites become abundant. Furthermore, diet manipulation and artificial selection experiments also showed that the exaggerated leg length in M. longipes males is influenced by both genetic and nutritional factors. Collectively, our results highlight how fluctuation in the strength of directional sexual selection, through changes in the intensity of male competition, can drive the exaggeration and phenotypic variation in this weapon trait.

scholarly journals Age-dependent female responses to a male ejaculate signal alter demographic opportunities for selection

2013 ◽  
Vol 280 (1766) ◽  
pp. 20130428 ◽  
Author(s):  
Claudia Fricke ◽  
Darrell Green ◽  
Walter E. Mills ◽  
Tracey Chapman
Keyword(s):  
Sexual Conflict ◽  
Seminal Fluid ◽  
Conflicts Of Interest ◽  
Egg Laying ◽  
Specific Expression ◽  
Young Females ◽  
Sexually Selected Traits ◽  
Selected Traits ◽  
Female Responses ◽  
Seminal Fluid Protein

A central tenet of evolutionary explanations for ageing is that the strength of selection wanes with age. However, data on age-specific expression and benefits of sexually selected traits are lacking—particularly for traits subject to sexual conflict. We addressed this by using as a model the responses of Drosophila melanogaster females of different ages to receipt of sex peptide (SP), a seminal fluid protein transferred with sperm during mating. SP can mediate sexual conflict, benefitting males while causing fitness costs in females. Virgin and mated females of all ages showed significantly reduced receptivity in response to SP. However, only young virgin females also showed increased egg laying; hence, there was a narrow demographic window of maximal responses to SP. Males gained significant ‘per mating’ fitness benefits only when mating with young females. The pattern completely reversed in matings with older females, where SP transfer was costly. The overall benefits of SP transfer (hence opportunity for selection) therefore reversed with female age. The data reveal a new example of demographic variation in the strength of selection, with convergence and conflicts of interest between males and ageing females occurring over different facets of responses to a sexually antagonistic trait.

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

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.

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 A conserved trans regulatory loop involving an odorant binding protein controls male mating behavior in flies

2021 ◽  
Author(s):  
Pablo J Delclos ◽  
Kiran Adhikari ◽  
Oluwatomi Hassan ◽  
Alexander A Oderhowho ◽  
Vyshnika Sriskantharajah ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Mating Behavior ◽  
House Fly ◽  
Male Mating ◽  
Sexually Selected Traits ◽  
Y Chromosomes ◽  
Male Mating Behavior ◽  
Selected Traits ◽  
Regulatory Loop ◽  
Odorant Binding

A major goal in evolutionary biology is to understand how natural variation is maintained in sexually selected and sexually dimorphic traits. Hypotheses to explain genetic variation in sexually selected traits include context-dependent fitness effects, epistatic interactions, and pleiotropic constraints. The house fly, Musca domestica, is a promising system to investigate how these factors affect polymorphism in sexually selected traits. Two common Y chromosomes (YM and IIIM) segregate as stable polymorphisms in natural house fly populations, appear to be locally adapted to different thermal habitats, and differentially affect male mating success. Here, we perform a meta-analysis of RNA-seq data which identifies genes encoding odorant binding proteins (in the Obp56h family) as differentially expressed between the heads of males carrying YM and IIIM. Differential expression of Obp56h has been associated with variation in male mating behavior in Drosophila melanogaster. We find differences in male mating behavior between house flies carrying the Y chromosomes that are consistent with the relationship between male mating behavior and expression of Obp56h in D. melanogaster. We also find that male mating behaviors in house fly are affected by temperature, and the same temperature differentials further affect the expression of Obp56h genes. However, we show that temperature-dependent effects cannot explain the maintenance of genetic variation for male mating behavior in house fly. Using a network analysis and allele-specific expression measurements, we find evidence that the house fly IIIM chromosome is a trans regulator of Obp56h gene expression. Moreover, we find that Obp56h disproportionately affects the expression of genes on the D. melanogaster chromosome that is homologous to the house fly IIIM chromosome. This provides evidence for a conserved trans regulatory loop involving Obp56h expression that affects male mating behavior in flies. The complex regulatory architecture controlling Obp56h expression suggests that variation in male mating behavior could be maintained by epistasis or pleiotropic constraints.

Tests of the positive and functional allometry hypotheses for sexually selected traits in the Jamaican field cricket

2021 ◽  
pp. 104413
Author(s):  
Susan M. Bertram ◽  
Danya D. Yaremchuk ◽  
Mykell L. Reifer ◽  
Amy Villareal ◽  
Matthew J. Muzzatti ◽  
...  
Keyword(s):  
Field Cricket ◽  
Sexually Selected Traits ◽  
Selected Traits
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