Conservation Genetics in Mammals by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030333348
Publisher: Springer International Publishing

5.2 Genetic Diversity and Possible Demographic Changes in the Andean Bear

We found that the mtDNA and nuclear and patterns of genetic diversity in the Andean bear were not concordant. The mt genetic diversity was high for the overall species, as well as in each one of the ESUs (Hd = 0.89–0.94; π = 0.013–0.019). These levels are within the range, or slightly lower, of that detected in other medium–large Neotropical carnivores with elevated genetic diversity [Cerdocyon thous, (Hd = 0.83, π = 0.019; Tchaicka et al. 2006); Eira barbara (Hd = 0.98, π = 0.042; Ruiz-García et al. 2017a); Leopardus colocolo (Hd = 0.93, π = 0.051; Ruiz-García et al. 2013a); Leopardus pardalis (Hd = 0.96, π = 0.068; Eizirik et al. 1998); Leopardus wiedii (Hd = 0.98, π = 0.079; Eizirik et al. 1998); Lontra longicaudis (Hd = 0.90, π = 0.011; Trinka et al. 2012; Hd = 0.98, π = 0.011; Ruiz-García et al. 2018); Panthera onca (Hd = 0.99–0.94, π = 0.027–0.01; Eizirik et al. 2001; Ruiz-García et al. 2013b) Potos flavus (Hd = 0.99, π = 0.02–0.07; Ruiz-García et al. 2019)].

Nevertheless, the nuclear genetic diversity in the Andean bear is moderate for microsatellite markers. The average microsatellite H was around 0.55. This value is lower than in other bear species. Waits et al. (2000) showed that the genetic diversity values for several brown bear studies across North America and Scandinavia with the same markers we used ranged from 0.61 to 0.78 (an average of H = 0.74). Paetkau and Strobeck (1994) determined the microsatellite genetic diversity for two continental Canadian populations of the American black bears (U. americanus), to be around 0.8. Thus, it seems that the Andean bear has a nuclear genetic diversity lower than other bears. The usual pattern for a species with large-effective numbers and constant size throughout time should be high levels of genetic diversity for both kinds of markers. The usual pattern for a species, which has crossed a population reduction with a posterior expansion process, should be a low or null mtDNA genetic diversity, and moderate nuclear microsatellite diversity. These patterns are the result of differences in effective population size. The effective population size with mtDNA is considerably lower than with nuclear DNA (Allendorf and Luikart 2007). Thus, genetic drift has stronger effects on the mtDNA than on the nuclear DNA. Nonetheless, in contrast, we found higher genetic diversity for the mt markers than for the nuclear markers. A possible explanation to this paradox is the effect of “ascertainment bias” (Ellegren et al. 1995, 1997; Amos and Rubinsztein 1996), in which the species to whose microsatellites were applied usually show a lower genetic diversity than the target species. This effect cannot be discarded because the microsatellites employed in this study for the Andean bear were designed for the American black bear, and the split for the common ancestor of the two species has been dated to have occurred around 15–12 MYA (Waits et al. 1999). To resolve this question, it is necessary to design specific microsatellites for the Andean bear. However, some specific demographic changes should be not discarded because of the different evolutionary time scales of nuclear markers and mtDNA (Manisse et al. 2018).

All the mt analyses for the overall sample, as well as for each one of the ESUs, showed evidences of female population expansions.

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