Asymmetric competition impacts evolutionary rescue in a changing environment

Abstract

Interspecific competition can strongly influence the evolutionary response of a species to a changing environment, impacting the chance that the species survives or goes extinct. Previous work has shown that when two species compete for a temporally shifting resource distribution, the species lagging behind the resource peak is the first to go extinct due to competitive exclusion. However, this work assumed symmetrically distributed resources and competition. Asymmetries can generate differences between species in population sizes, genetic variation and trait means. We show that asymmetric resource availability or competition can facilitate coexistence and even occasionally cause the leading species to go extinct first. Surprisingly, we also find cases where traits evolve in the opposite direction to the changing environment because of a 'vacuum of competitive release' created when the lagging species declines in number. Thus, the species exhibiting the slowest rate of trait evolution is not always the most likely to go extinct in a changing environment. Our results demonstrate that the extent to which species appear to be tracking environmental change and the extent to which they are preadapted to that change may not necessarily determine which species will be the winners and which will be the losers in a rapidly changing world.

Earlier phenology of a nonnative plant increases impacts on native competitors

“…We might also expect the native species in our focal ecosystem to exert selection on L. serriola, with potential implications for L. serriola's ability to adapt to the environment in the absence of competition, although we were not able to test this hypothesis with our data. Previous work has shown that species' interactions can have both negative and positive effects on adaptation to changing environmental conditions (42)(43)(44)(45)(46), partly depending on whether biotic and abiotic selection pressures are aligned (47,48). Nonetheless, selection by native species on L. serriola is likely minimal, since even the local L. serriola population in our experiment flowered later than all native species, and a previous study in this system found that late phenology species, including L. serriola, were competitively dominant in experimental arrays (16,17).…”

Evolutionarily stable communities: a framework for understanding the role of trait evolution in the maintenance of diversity

“…This outcome is a kind of evolutionary rescue, where trait evolution can rescue a population from a declining trajectory (Gomulkiewicz & Holt 1995). Theory and empirical studies have documented conditions under which evolutionary rescue is possible, both in isolation (Gomulkiewicz & Holt 1995;Bell & Gonzalez 2009) and in the presence of competition (Osmond & de Mazancourt 2013;Van Den Elzen et al 2017); trait convergence may require similar conditions. The possibility of trait (or character) convergence has large implications for our understanding of species diversity and its relationship to functional diversity (Abrams 1990;terHorst et al 2010;Klauschies et al 2016).…”

Evolutionary responses to global change in species‐rich communities

“…However, as indicated by these two contrasting examples, general predictions may be elusive; recent theory illustrates how shifts in resource availability and competition interact to influence evolution, sometimes in complex and surprising ways where traits change in a direction counter to the shift in resource availability. 31,32 Nutrient availability also influences trophic interactions. For example, elevated atmospheric CO 2 conditions alters plant-herbivore interactions because plant tissues typically have higher C:N ratios that frequently makes them less palatable to insect herbivores, although increased damage has also been observed in response to elevated CO 2 , as insect herbivores must consume more plant tissue to meet nutritional needs.…”