Читать книгу Fundamentals of Conservation Biology - Malcolm L. Hunter Jr. - Страница 112

Effective population size (N_e) is a critical piece of information for management of many rare species. In theory it is easy to count the number of individuals in the field, pass the numbers through some formulae, and estimate N_e. In reality, many creatures are very difficult to count in the wild (too rare, too shy, too cryptic, etc.). Genetic methods offer an alternative. One can estimate N_e by looking at the change in heterozygosity over time, something that can be done with historical and contemporary genetic samples. Genotypes can also be used as “tags,” like the bird rings and other crude methods biologists use to mark animals and estimate their population sizes through mark–recapture methods. This is particularly helpful for estimating populations of animals that are challenging to catch and mark, like grizzly bears (Kendall et al. 2016) or great white sharks (Andreotti et al. 2016), but whose DNA you can sample without catching them, for example from their hair left on trees, or feces on the ground or in the water. Signatures of population history can also be found in genetic data that provide insights into whether a population has declined, expanded, or remained stable over recent generations (Garrick et al. 2014).