Eco‐evolutionary extinction and recolonization dynamics reduce genetic load and increase time to extinction in highly inbred populations

Abstract

Understanding how genetic and ecological effects can interact to shape genetic loads within and across local populations is key to understanding ongoing persistence of systems that should otherwise be susceptible to extinction through mutational meltdown. Classic theory predicts short persistence times for metapopulations comprising small local populations with low connectivity, due to accumulation of deleterious mutations. Yet, some such systems have persisted over evolutionary time, implying the existence of mechanisms that allow metapopulations to avoid mutational meltdown. We first hypothesize a mechanism by which the combination of stochasticity in the numbers and types of mutations arising locally (genetic stochasticity), resulting local extinction, and recolonization through evolving dispersal facilitates metapopulation persistence. We then test this mechanism using a spatially and genetically explicit individual‐based model. We show that genetic stochasticity in highly structured metapopulations can result in local extinctions, which can favor increased dispersal, thus allowing recolonization of empty habitat patches. This causes fluctuations in metapopulation size and transient gene flow, which reduces genetic load and increases metapopulation persistence over evolutionary time. Our suggested mechanism and simulation results provide an explanation for the conundrum presented by the continued persistence of highly structured populations with inbreeding mating systems that occur in diverse taxa.

Evaluation of DSSAT CROPGRO model on growth and yield of pigeonpea cultivars under different fertigation levels

“…both sexes are equally produced) (Abbes and Chermiti, 2014;Grant et al,2021). A further plausible scenario involves a recurrent population extinction and colonizations that reduce genuine genetic diversity (Charmouh et al,2022). One scenario that meets this criterion is when T. absoluta populations are exposed to local extinction by synthetic pesticides, which is the major strategy for the management of T. absoluta in India.…”

Environmental variance in male mating success modulates the positive versus negative impacts of sexual selection on genetic load

“…However, while we considered a single isolated population, natural populations may often exist in a metapopulation context where, all else equal, gene flow is expected to counteract local fixation of deleterious mutations via outcrossing and thus increase the efficacy of selection (Theodorou & Couvet, 2002, 2006), thereby increasing persistence times of local subpopulations. In addition, extinction‐recolonization dynamics may increase meta‐population persistence times when empty habitat patches are recolonized by high fitness genotypes (Charmouh et al, 2022). Thus, our current model opens numerous possibilities for future extensions to evaluate the balance between positive and negative effects of sexual selection, encompassing spatial structure and different regimes of beneficial alongside deleterious mutations.…”