Genetic diversity and fitness in small populations [chapter]

R. C. Vrijenhoek
1994 Conservation Genetics  
10 Human-driven habitat fragmentation and loss has led to a proliferation of small and isolated 11 plant and animal populations that may be threatened with extinction by genetic factors. The 12 prevailing approach for managing these populations is to maintain high genetic diversity, which 13 is often equated with fitness. Increasingly, this is being done using genetic rescue, where 14 individuals from populations with high genetic diversity are translocated to small populations 15 with high
more » ... ns 15 with high levels of inbreeding. However, the potentially negative consequences of this 16 approach have recently been highlighted by the demise of the gray wolf population on Isle 17 Royale, which only briefly recovered after genetic rescue by a migrant from the large mainland 18 wolf population and then declined to the brink of extinction. Here, we use ecologically-19 motivated population genetic simulations to show that extinction risk in small populations is 20 often increased by maximizing genetic diversity but is consistently decreased by minimizing 21 deleterious variation. Surprisingly, we find that small populations that are founded or rescued 22 by individuals from large populations with high genetic diversity have an elevated risk of 23 extinction due to the high levels of recessive deleterious variation harbored by large 24 populations. By contrast, we show that genetic rescue or founding from small or moderate-25 sized populations leads to decreased extinction risk due to greater purging of strongly 26 deleterious variants. Our findings challenge the traditional conservation paradigm that focuses 27 on genetic diversity in assessing extinction risk in favor of a new view that emphasizes 28 minimizing deleterious variation. These insights have immediate implications for managing 29 small and isolated populations in the increasingly fragmented landscape of the Anthropocene. 30 31 32 . CC-BY-NC-ND 4.0 International license is made available under a
doi:10.1007/978-3-0348-8510-2_5 fatcat:rhuwjj5oejhszemeb2ur7mdqmy