Genetic consequences of population decline in the European otter (Lutra lutra): an assessment of microsatellite DNA variation in Danish otters from 1883 to 1993

Abstract

The European otter (Lutra lutra) was common in Denmark until the 1960s, but its present distribution encompasses only a minor part of the country. The aim of this study was to assess whether the recent population decline has resulted in loss of genetic variability and to gain further insight into the dynamics of the population decline. This was done by analysing microsatellite DNA variation in contemporary and historical samples, the latter encompassing DNA samples extracted from museum specimens covering a time-span from the 1880s to the 1960s. Tests for di¡erences in expected heterozygosity and the numbers of alleles in contemporary versus historical samples and a test for detecting population bottlenecks provided few indications of a recent bottleneck and loss of variability. However, a procedure for detecting population expansions and declines, based on the genealogical history of microsatellite alleles, suggested that a drastic long-term population decline has taken place, which could have started more than 2000 years ago, possibly due to ancient anthropogenic pressure. Finally, assignment tests and pairwise F ST values suggested weak but statistically signi¢cant genetic di¡erentiation between the extant population and historical samples of otters from other regions in Denmark, more likely re£ecting di¡erentiation among original populations rather than recent drift.

Back to the future: museum specimens in population genetics

“…Such 'ghost alleles' have subsequently been reported in several bottlenecked animal populations. By contrast, other studies have reported stable genetic diversity despite declines in population size [24][25][26]. For example, no obvious loss of genetic diversity was detected among Canadian peregrine falcons (Falco peregrinus) despite a DDT induced bottleneck [25].…”

Low Genetic Variation in the Heath Hen Prior to Extinction and Implications for the Conservation of Prairie-Chicken Populations

“…To date, relatively few studies of wild populations have examined the loss of genetic variation over the course of a population decline or recovery. In some populations there has been a significant loss of both genetic variation and fitness (Westemeier et al 1998), but in other cases the results are less clear, as the genetic changes have been relatively small (Miller and Waits 2003), the loss of genetic variation predated the population decline (Mundy et al 1997;Pertoldi et al 2001) or the loss of genetic variation was associated with relatively minor effects on fitness (Weber et al 2000;Groombridge et al 2000, Bellinger et al 2003. To date, only two studies of populations in the wild have demonstrated a positive association between genetic variation and the risk of population extinction (Newman and Pilson 1997;Saccheri et al 1998).…”

Decline of North Atlantic eels: a fatal synergy?

“…New tools based on Bayesian statistics and coalescence theory are now available (Beaumont 1999;Pertoldi et al 2001;Storz & Beaumont 2002) to determine these from genetic data. Here, we used the procedure of Beaumont (1999) to detect population declines and expansions.…”