Evolutionary rescue

Populations that decline towards extinction can be evolutionary rescued by a natural selection acceleration of the growth rate

As natural selection in the absence of interactive competition approaches Fisher’s (1930) fundamental theorem, populations that decline in numbers should eventually converge on a natural selection acceleration of growth rates. If this acceleration is sufficiently large compared with the rate of decline, the population is evolutionary rescued by natural selection before it goes extinct.

Fig. 1 Three examples of evolutionary rescue from Witting (2021). A hyperexponential model is used for a population of white-crowned sparrow from the North American Breeding Bird Survey (Sauer et al., 2017), and for common cuckoo from BTO (2020). A selection-regulated model is used for a population of American black bear from the Global Population Dynamic Database (2010).

The process of evolutionary rescue was introduced by Pease et al. (1989), and the term was used for the first time by Gomulkiewicz and Holt in 1995. Evolutionary rescue is typically studied in relation to populations that decline due to environmental changes (Ramsayer et al., 2013; Bell, 2017). But the process is likely to be much more common. Selection-regulated populations with cyclic dynamics e.g., are often saved from extinction by natural selection during the low phase of a cycle.

Selection accelerating populations that decline in numbers are often evolutionarily rescued due to the continued natural selection acceleration of their growth rate. The passenger pigeon in North America, however, is an example of a species that wasn’t evolutionary rescued as it continued on a drastic decline from about 1870 until extinction in the wild around 1901 (the last individual in captivity died in 1914).

References

Bell, G. 2017. Evolutionary rescue. Annual Review of Ecology, Evolution, and Systematics 48:605--627.
BTO 2020. British Trust for Ornithology. Population trend graphs. https://www.bto.org.
Fisher, R.A. 1930. The genetical theory of natural selection. Clarendon, Oxford.
Gomulkiewicz, R., and R.D. Holt 1995. When does evolution by natural selection prevent extinction?. Evolution 49:201--207.
GPDD 2010. The Global Population Dynamics Database v2.0. NERC Centre for Population Biology, Imperial College, http://www.sw.ic.ac.uk/cpb/cpb/gpdd.html.
Pease, C., R.Lande and J.Bukk 1989. A model of population growth, dispersal and evolution in a changing environment. Ecology 70:1657--1664.
Ramsayer, J., O.Kaltz and M.E. Hochberg 2013. Evolutionary rescue in populations of Peudomonas fluoresens across an antibiotic gradient. Evolutionary Applications 6:608--616.
Sauer, J.R., D.K. Niven, J.E. Hines, D.J. Ziolkowski, K.L. Pardieck, J.E. Fallon and W.A. Link 2017. The North American Breeding Bird Survey, Results and analysis 1996 -- 2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, Maryland, Available at www.mbr-pwrc.usgs.gov/bbs/bbs.html.
Witting, L. 2021. Selection-regulated population dynamic in birds and mammals. Preprint at bioRxiv https://dx.doi.org/10.1101/2021.11.27.470201.