Evolutionary rescue is a process by which a population—that would have gone extinct in the absence of evolution—persists due to natural selection acting on heritable variation.[1][2] The term was first used in 1995 by Gomulkiewicz and Holt [3] in the context of a sudden environmental change, but the process was studied long before in the context of continuous environmental change[4] and, especially, drug resistance evolution.[5]
Theoretical framework
After a sudden change in the environment, evolutionary rescue is predicted to create a U-shaped curve of population dynamics, as the original genotypes, which are unable to replace themselves, are replaced by genotypes that are able to increase in numbers.[3] In a continuously changing environment, evolutionary rescue is predicted to appear as a stable lag of the mean trait value behind a moving environmental optimum, where the rate of evolution and rate of change in the environment are equal.[6] The theory has been reviewed by Alexander et al in 2014 [7] and continues to grow rapidly, adding both genetic and ecological complexity.
a theoretical depiction of evolutionary rescue.Evolutionary rescue is expected to produce a U-shaped curve of population dynamics after a sudden change in the environment, as genotypes that are unable replace themselves are replaced by those that can. Figure from [8]
Evolutionary rescue is distinct from demographic rescue, where a population is sustained by continuous migration from elsewhere, without the need for evolution.[9] On the other hand, genetic rescue, where a population persists because of migration that reduces inbreeding depression, can be thought of a special case of evolutionary rescue (but see [8]).
Empirical evidence
Evolutionary rescue has been demonstrated in many different experimental evolution studies,[1] such as yeast evolving to tolerate previously lethal salt concentrations.[10]
There are also a large number of examples of evolutionary rescue in the wild,[1] in the forms of drug resistance, herbicide resistance,[11] other types of pesticide resistance, and genetic rescue.
