Experimental evolution reveals balancing selection underlying coexistence of alternative male reproductive phenotypes.

Heritable alternative reproductive phenotypes (ARPs), which differ in traits associated with competition for mates, occur across taxa. If polymorphism in the genes underlying ARPs is maintained by balancing selection, selection should return ARP proportions to their equilibrium if that equilibrium is perturbed. Here, we used an experimental evolution approach to directly test this prediction in male Rhizoglyphus robini, in which two heritable morphs occur: armored fighters and more female-like, benign scramblers.

Transcriptomics of Intralocus Sexual Conflict: Gene Expression Patterns in Females Change in Response to Selection on a Male Secondary Sexual Trait in the Bulb Mite.

Intralocus sexual conflict (IASC) prevents males and females from reaching their disparate phenotypic optima and is widespread, but little is known about its genetic underpinnings. In Rhizoglyphus robini, a mite species with alternative male morphs, elevated sexual dimorphism of the armored fighter males (compared to more feminized scramblers males) was previously reported to be associated with increased IASC. Because IASC persists if gene expression patterns are correlated between sexes, we compared gene expression patterns of males and females from the replicate lines selected for increased proportion of fighter or scrambler males (F- and S-lines, respectively).

Selection for alternative male reproductive tactics alters intralocus sexual conflict.

Intralocus sexual conflict (IASC) arises when fitness optima for a shared trait differ between the sexes; such conflict may help maintain genetic variation within populations. Sex-limited expression of sexually antagonistic traits may help resolve the conflict, but the extent of this resolution remains a subject of debate. In species with alternative male reproductive tactics, unresolved conflict should manifest more in a more sexually dimorphic male phenotype.

No evidence for reproductive isolation through sexual conflict in the bulb mite Rhizoglyphus robini.

Sexual conflict leading to sexual antagonistic coevolution has been hypothesized to drive reproductive isolation in allopatric populations and hence lead to speciation. However, the generality of this speciation mechanism is under debate. We used experimental evolution in the bulb mite Rhizoglyphusrobini to investigate whether sexual conflict promotes reproductive isolation measured comprehensively to include all possible pre- and post-zygotic mechanisms.

Mating system affects population performance and extinction risk under environmental challenge.

Failure of organisms to adapt to sudden environmental changes may lead to extinction. The type of mating system, by affecting fertility and the strength of sexual selection, may have a major impact on a population's chances to adapt and survive. Here, we use experimental evolution in bulb mites (Rhizoglyphus robini) to examine the effects of the mating system on population performance under environmental change.