Sex increases the probability of evolutionary rescue in the presence of a competitor

Abstract

The explanation for the continued existence of sex, despite its many costs, remains one of the major challenges of evolutionary biology. Previous experimental studies have demonstrated that sex increases the rate of adaptation in novel environments relative to asexual reproduction. Whereas these studies have investigated the impact of sex on adaptation to stressful abiotic environments, the potential for biotic interactions to influence this advantage of sex has been largely ignored. Species rarely exist in isolation in natural conditions, so the impact of sex on adaptation to a stressful abiotic environment may be altered by the interactions between coexisting species. To investigate the interplay of sex and competition on adaptation to deteriorating conditions, we allowed populations of the unicellular alga (Chlamydomonas reinhardtii) to evolve in an environment to which they were initially poorly adapted. We manipulated both their mode of reproduction and the presence of a competitor, and monitored population size and proportion of evolutionary rescue events for each mode of reproduction. The results indicate that sex may be the beneficial strategy in the presence of the competitor. Sexual populations had highest probability of evolutionary rescue irrespective of the presence of the competitor. The overall advantage of sex was also manifested through higher level of adaptedness of survived sexual populations relative to asexual populations. Since competitive interactions are commonplace in nature, one of the explanations for the maintenance of sex by natural selection may be the increased rate of adaptation of sexual populations both in the presence and absence of competitors.

Ecological limits to evolutionary rescue

“…'press', environmental changes (e.g. [30][31][32][33][34][35][36][37]). Experiments that expose communities to gradual change (e.g.…”

Frequent sexual reproduction limits adaptation in outcrossed populations of the algaChlamydomonas reinhardtii

“…Recent experimental work has demonstrated that sexual reproduction may speed up adaptation of species. For example, evolution experiments with populations of algae [8,9], protists [10][11][12][13] and yeast [14,15] have demonstrated that sexual reproduction can facilitate adaptation of populations to their biotic or abiotic environment. Additionally, it has been shown experimentally that sexual reproduction is under positive selection when environmental complexity increases [12,16].…”

Evolutionary rescue can prevent rate-induced tipping

“…The relation between different time scales is also key to another ecological phenomenon, called evolutionary rescue, where populations are able to rescue themselves from extinction by rapid evolution (Gomulkiewicz and Holt 1995;Bell 2013;Gonzalez et al 2013;Bell and Gonzalez 2009;Gomulkiewicz and Shaw 2013;Carlson et al 2014). Naturally, whether populations are able to adapt sufficiently fast to rapid environmental change depends on their interactions with other species (Lavergne et al 2010;Lawrence et al 2012;Van der Putten et al 2010;Schoener et al 2001;Bastille-Rousseau et al 2018) and some studies have in fact treated evolutionary rescue in a multi-species context (Henriques and Osmond 2020;De Mazancourt et al 2008;Petkovic and Colegrave 2019;Northfield and Ives 2013;Norberg et al 2012;Kovach-Orr and Fussmann 2013;Osmond and de Mazancourt 2013), e.g., in predator-prey systems (Osmond et al 2017;Yamamichi and Miner 2015;Yamamichi et al 2019;Cortez and Yamamichi 2019). In one of these works, Yamamichi and Miner (2015) demonstrate that rapid evolution of a prey species alone can rescue its non-evolving predator from extinction.…”