Maintenance of genetic diversity in cyclic populations—a longitudinal analysis inMyodes glareolus

Abstract

Conspicuous cyclic changes in population density characterize many populations of small northern rodents. The extreme crashes in individual number are expected to reduce the amount of genetic variation within a population during the crash phases of the population cycle. By long-term monitoring of a bank vole (Myodes glareolus) population, we show that despite the substantial and repetitive crashes in the population size, high heterozygosity is maintained throughout the population cycle. The striking population density fluctuation in fact only slightly reduced the allelic richness of the population during the crash phases. Effective population sizes of vole populations remained also relatively high even during the crash phases. We further evaluated potential mechanisms contributing to the genetic diversity of the population and found that the peak phases are characterized by both a change in spatial pattern of individuals and a rapid accession of new alleles probably due to migration. We propose that these events act together in maintaining the high genetic diversity within cyclical populations.

Food resources and intestinal parasites as limiting factors for boreal vole populations during winter

“…A standard was prepared by combining 2 ml from each sample over all trapping occasions. Duplicate standard concentrations of 200,150,100,50,25,10,5 and 0 were run on each plate simultaneously with samples. Plates containing samples and standards were then incubated for 3 hours at room temperature.…”

“…Populations of northern small mammals are renowned for their high-amplitude density cycles, with peaks every 3-5 years [1][2][3][4][5]. Although delayed density-dependent predation is often considered the principle driver of cyclic dynamics [6][7][8][9][10], regulatory processes are likely to be multifactorial and geographically variable [1,11].…”

Genetic monitoring to evaluate reintroduction attempts of a highly endangered rodent

“…On the other hand, large population fluctuations are typical for rodents like the Common hamster (Krebs 2013) and genetic diversity and effective population size can be maintained in rodents through migration (Rikalainen et al 2012). Unfortunately, the current populations of Common hamster in Belgium and the Netherlands are highly isolated, which reduces the change of maintenance of genetic diversity through natural immigration drastically (La Haye et al 2012a).…”

“…Such a population crash is a real threat for the highly endangered hamster populations in Belgium and the Netherlands, as all hamster populations already have an impoverished genetic diversity (La Haye et al 2012a) and a crash may result in a further loss of genetic variation and a reduction of the effective population size (Allendorf et al 2013;Keller et al 2012;Luikart et al 2010;McEachern et al 2011). Effective population sizes (Table 1) On the other hand, large population fluctuations are typical for rodents like the Common hamster (Krebs 2013) and genetic diversity and effective population size can be maintained in rodents through migration (Rikalainen et al 2012). Unfortunately, the current populations of Common hamster in Belgium and the Netherlands are highly isolated, which reduces the change of maintenance of genetic diversity through natural immigration drastically (La Haye et al 2012a).…”

Gene flow counteracts the effect of drift in a Swiss population of snow voles fluctuating in size

“…The positive effect of immigration on genetic variability is the result of immigrants introducing novel alleles into the pool of local alleles, which can increase heterozygosity and offset the potentially negative effects of inbreeding (Keller and Waller, 2002;Westemeier et al, 1998;Marr et al, 2002). Hence, a rapid accumulation of new alleles through immigration can contribute to the maintenance of high levels of genetic variability in fluctuating populations (Ehrich and Jorde, 2005;Rikalainen et al, 2012;Gauffre et al, 2014). Furthermore, in addition to being different, the alleles introduced by immigrants may increase in fitness by increasing heterozygosity (i.e., overdominance effect), as only more heterozygous individuals may be able to successfully disperse into a new population (e.g., Selonen and Hanski, 2010;García-Navas et al, 2014).…”