The Effect of Habitat Choice on Evolutionary Rescue in Subdivided Populations

Abstract

Evolutionary rescue is the process by which a population, in response to an environmental change, successfully avoids extinction through adaptation. In spatially structured environments, dispersal can affect the probability of rescue. Here, we model an environment consisting of patches that degrade one after another, and we investigate the probability of rescue by a mutant adapted to the degraded habitat. We focus on the effects of dispersal and of immigration biases. We identify up to three regions delimiting the effect of dispersal on the probability of evolutionary rescue: (i) starting from low dispersal rates, the probability of rescue increases with dispersal;(ii) at intermediate dispersal rates, it decreases; and (iii) at large dispersal rates, it increases again with dispersal, except if mutants are too counterselected in not-yet-degraded patches. The probability of rescue is generally highest when mutant and wild-type individuals preferentially immigrate into patches that have already undergone environmental change. Additionally, we find that mutants that will eventually rescue the population most likely first appear in nondegraded patches. Overall, our results show that habitat choice, compared with the often-studied unbiased immigration scheme, can substantially alter the dynamics of population survival and adaptation to new environments.

The role of spatial structure in multi‐deme models of evolutionary rescue

“…But since we do not expect gene flow to be isotropic in natural systems, because of physical barriers over the habitat and habitat range limits, it is difficult to predict whether chances of evolutionary rescue would increase or decrease when widening the migration kernel, due to the effects on evolutionary rescue when gene flow is not isotropic (see Kawecki & Holt, 2002;Tomasini & Peischl, 2020 for a discussion of asymmetric gene flow). In addition, Czuppon et al (2021) studied the effects of biased migration on local adaptation and evolutionary rescue, using the same setting as in our current work. They show that dispersal schemes in which migration has a larger chance to occur towards deteriorated habitats increase the probability of rescue.…”

“…For instance, in the face of structured populations, it has been demonstrated both experimentally (Bell & Gonzalez, 2009Gonzalez & Bell, 2013) and theoretically (Czuppon et al, 2021;Uecker et al, 2014) that gene flow between sub-populations can facilitate evolutionary rescue. The benefits of spatial structures and dispersal to local adaptation and evolutionary rescue have also been demonstrated in other contexts.…”

“…Experimental and theoretical work suggests, however, that the spatial organization of sub-populations, as well as biased dispersal, modulate the effect of gene flow (Bell & Gonzalez, 2011;Czuppon et al, 2021;Gonzalez & Bell, 2013). The experimental results from Bell and Gonzalez (2011) suggest that the probability for evolutionary rescue depends both on the rate at which the environment deteriorates across space as well as on how migration was implemented in their experiments (localized vs. global migration).…”

Surviving environmental change: when increasing population size can increase extinction risk

“…Such a scenario is reminiscent of Wright’s shifting balance theory [26,27], though our analysis focuses narrowly on the probability of extinction or adaptation after an environmental change via a specific survival allele, rather than on adaptation on complex landscapes. Previous theoretical work on rescue in a structured population has identified a counterintuitive non-monotonic response of the rescue probability to the migration rate [23,28] and the rate of environmental degradation [23]. Future work could characterize the effect of population size in a structured population, noting that small subpopulations would be subject to the accumulation of other deleterious genes that would further endanger them [17,25].…”

Facilitated Adaptation as A Conservation Tool in the Present Climate Change Context: A Methodological Guide

“…On the other hand, if favorable alleles are found, the risk of losing them through genetic drift is greater, even if they are of adaptive value [ 38 , 52 ]. Interestingly, a number of theoretical models and experimental studies have highlighted the impact of migration on the probability of evolutionary rescue [ 37 , 53 , 54 , 55 ]. For example, Tomasini and Peischl [ 56 ] have showed in a two-deme model that migration favors evolutionary rescue when (a) environmental change occurs slowly across two populations (which leaves time for the second population to serve as a migration source), (b) the new environment is very harsh and (c) rescue mutations are strongly beneficial in the new environment.…”