Rapid evolutionary adaptation: Potential and constraints

Abstract

The vast diversity of life on earth is the result of evolutionary processes that acted over billions of years. Historically it was assumed that adaptation and the origin of new species required long periods of time. However, it is now well established that adaptation to new environments can occur rapidly and sometimes even within a few generations. We define here rapid adaptation as a selective process, which allows a population or species to substantially improve its average fitness in the short time scale of few tens of generations, typically within a hundred years for annual species. More precisely, rapid adaptation occurs through natural selection acting on the phenotype (and ultimately on the underlying genetic variants) over short time scale and therefore encompasses both ecological (demographic abundance and inter-specific interactions within a given habitat and species community) and evolutionary (genetic drift, mutation, recombination, gene flow and selection) processes (Hairston et al., 2005;Kokko et al., 2017). The occurrence and speed of rapid adaptation is thus determined by the feedback between ecological and evolutionary (eco-evo) processes. A large body of literature now documents