Biology subjects

Servedio, M. R.

Publications and source records attributed to Servedio, M. R..

4 recordsLinked to original sources

bioRxiv2024

When does sexual selection through mate choice deplete versus exaggerate genetic variation: is there a lek paradox?

The evolution of female preferences for male display traits relies on females receiving indirect benefits from their mate. This requires substantial genetic variation in display traits or male quality. Nevertheless, sexual selection through mate choice has been assumed to deplete this genetic variation, ultimately diminishing strong preferences. However, sexual traits often have higher genetic variation than non-sexual traits. This contradiction, and, relatedly, how costly preferences and display traits are maintained, is called the "lek paradox". Using infinitesimal models, we show that sexual selection through mate choice allows variation in male display traits and female preferences to mutually exaggerate each other, in a process analogous to runaway sexual selection but in terms of genetic variation. Therefore, contrary to prior suppositions, sexual selection may increase equilibrium genetic variance in display traits and preferences over that under random mating, provided that the variance of female preferences relative to male traits during mate choice is not too small and preferences are not too weak. Notably, even if equilibrium preference variation is substantially smaller than trait variation, trait variation can still increase over that under random mating, provided selection on the trait compared to the preference is sufficiently strong. Furthermore, when trait variation does decrease, this reduction is generally slight. It is under situations such as lekking, where females can simultaneously choose from many males so that mate discrimination is effectively strong and fitness costs of choice weak, that sexual selection through mate choice may be most powerful in exaggerating genetic variance in male displays. Significance statementThe "lek paradox"--the dissonance between a hypothesized loss of variation in sexual display traits due to mate choice, leading to the subsequent cessation of sexual selection, and evidence of high variation in such traits in nature, accompanied by the long-term persistence of sexual selection--is an enduring mystery of the sexual selection literature. We clarify and quantify multiple pathways by which sexual selection via mate preferences alters genetic variance in both display traits and female preferences. Using mathematical models, we show the lek paradox is built upon a false premise. We find a wide range of conditions under which sexual selection increases or minimally reduces variation in display traits, allowing the maintenance of substantial variance in traits and preferences.

evolutionary biology↗

bioRxiv2023

Evolutionary rescue under demographic and environmental stochasticity

Wild populations suffer two types of stochasticity: demographic stochasticity, from sampling error in offspring number, and environmental stochasticity, from temporal variation of the growth rate. By modeling evolution through phenotypic selection following an abrupt environmental change, we investigate how genetic and demographic dynamics, as well as effects of selection intensity after the environmental change and genetic variance on population survival, differ under demographic and environmental stochasticity. We find that the survival probability declines sharply with stronger selection under demographic stochasticity, but declines more continuously under environmental stochasticity. However, the genetic variance that confers the highest survival probability differs little under demographic and environmental stochasticity. Since the influence of demographic stochasticity is stronger when population size is smaller, a slow initial decline of genetic variance which allows quicker evolution and increase of fitness, is important for persistence. In contrast, the influence of environmental stochasticity is density-independent, so higher initial fitness becomes important for survival under strong environmental stochasticity. Combining both types of stochasticity shows that adding even weak environmental stochasticity can exaggerate the effects of different levels of demographic stochasticity on survival probabilities. Our work suggests the importance of explicitly distinguishing and measuring the forms of stochasticity for evolutionary rescue studies.

evolutionary biology↗

bioRxiv2023

The effectiveness of pseudomagic traits in promoting premating isolation

Upon the secondary contact of populations, speciation with gene flow is greatly facilitated when the same pleiotropic loci are both subject to divergent ecological selection and induce non-random mating, leading to loci with this fortuitous combination of functions being referred to as "magic trait" loci. We use a population genetics model to examine whether "pseudomagic trait" complexes, composed of physically linked loci fulfilling these two functions, are as efficient in promoting premating isolation as magic traits. We specifically measure the evolution of choosiness, which controls the strength of assortative mating. We show that, surprisingly, pseudomagic trait complexes, and to a lesser extent also physically unlinked loci, can lead to the evolution of considerably stronger assortative mating preferences than do magic traits, provided polymorphism at the involved loci is maintained. This is because assortative mating preferences are generally favored when there is a risk of producing maladapted recombinants, as occurs with nonmagic trait complexes but not with magic traits (since pleiotropy precludes recombination). Contrary to current belief, magic traits may not be the most effective genetic architecture for promoting strong premating isolation. Distinguishing between magic traits and pseudomagic trait complexes is therefore important when inferring their role in premating isolation. This calls for further fine-scale genomic research on speciation genes.

evolutionary biology↗

bioRxiv2020

Same-sex sexual behavior and selection for indiscriminate mating

The widespread presence of same-sex sexual behavior (SSB) has long been thought to pose an evolutionary conundrum1-3, as participants in SSB suffer the cost of failing to reproduce after expending the time and energy to find a mate. The potential for SSB to occur as part of an optimal strategy has received almost no attention, although indiscriminate sexual behavior may be the ancestral mode of sexual reproduction4. Here, we build a simple model of sexual reproduction and create a theoretical framework for the evolution of indiscriminate sexual behavior. We provide strong support for the hypothesis that SSB is likely maintained by selection for indiscriminate sexual behavior, by showing that indiscriminate mating is the optimal strategy under a wide range of conditions. Further, our model suggests that the conditions that most strongly favor indiscriminate mating were likely present at the origin of sexual behavior. These findings have implications not only for the evolutionary origins of SSB, but also for the evolution of discriminate sexual behavior across the animal kingdom.

evolutionary biology↗