Inbreeding in the Greater White-Toothed Shrew, Crocidura Russula

Abstract

Abstract. We combined mark-and-recapture studies with genetic techniques of parentage assignment to evaluate the interactions between mating, dispersal, and inbreeding, in a free-ranging population of Crocidura russula. We found a pattern of limited and female-biased dispersal, followed by random mating within individual neighborhoods. This results in significant inbreeding at the population level: mating among relatives occurs more often than random, and F IT analyses reveal significant deficits in heterozygotes. However, related mating partners were not less fecund, and inbred offspring had no lower lifetime reproductive output. Power analyses show these negative results to be quite robust. Absence of phenotypic evidence of inbreeding depression might result from a history of purging: local populations are small and undergo disequilibrium gene dynamics. Dispersal is likely caused by local saturation and (re)colonization of empty breeding sites, rather than inbreeding avoidance. Because natural populations are finite in size, mating sometimes occurs among relatives, even when partners meet at random. Offspring born from such matings are said to be inbred, and they often display phenotypic abnormalities resulting in a loss of fitness through lower viability or fertility. This inbreeding depression has been repeatedly documented in a number of natural populations, including invertebrates

A comparative approach to testing hypotheses for the evolution of sex‐biased dispersal in bean beetles

“…Similarly, Duarte et al. (2003) found female‐biased dispersal in shrews despite evidence for polygyny and no negative fitness effects of inbreeding. These authors suggest that benefits of familiarity with natal territory could promote male philopatry or that local extinction/colonization dynamics could favor female dispersal as means to establish social groups in open habitat.…”

“…For example, the ability of males to acquire resources in their natal habitat or advantages of habitat familiarity could counteract selection for male‐biased dispersal (Greenwood 1980; Duarte et al. 2003). Benefits of philopatry in bean beetles are not well known but merit further study.…”

Conservation genetics of population bottlenecks: the role of chance, selection, and history

“…These studies, however, represent only indirect and inferential evidence on the potential role of purging. Non-significant declines in fitness in highly inbred populations have also been reported in Mexican and Red wolves (Kalinowski et al 1999), domestic cattle (Visscher et al 2001), White-toothed shrews (Duarte et al 2003), and experimental populations of Drosophila melanogaster (Fernández et al 2003). A review of the experimental evidence by Crnokrak and Barrett (2002) and of studies from captive populations by Boakes et al (2007) suggest, however, that purging may not be a strong force in small populations.…”

“…That is, while some populations showed signs of decreased genetic diversity and inbreeding depression, others revealed no declines or even increases in genetic variation and fitness following bottlenecks. Studies on inbreeding depression also documented non-significant declines in fitness in a wide variety of species, including wild populations (Kalinowski et al 1999;Duarte et al 2003), domestic species (Visscher et al 2001), and laboratory model organisms (Fernández et al 2003). The relationship between inbreeding and extinction has been even more complex, with only a few studies demonstrating a direct association between levels of genetic diversity, fitness, and extinction (e.g.…”

Genetic diversity-fitness correlation revealed by microsatellite analyses in European alpine marmots (Marmota marmota)

“…The strength of GDFCs in the wild is still debated. Studies reporting negative results exist (Rowe and Beebee 2001;Duarte et al 2003) and may be underrepresented because of publication bias in favour of positive results. On the other hand, many recent studies report a correlation between heterozygosity at neutral microsatellite markers and individual fitness-related traits such as survival (Coltman et al 1998;Coulson et al 1998Coulson et al , 1999Rossiter et al 2001;Markert et al 2004), reproductive success and recruitment (Slate et al 2000;Ho¨gl-und et al 2002;Foerster et al 2003;Hansson et al 2001Hansson et al , 2004Hoffman et al 2004;Markert et al 2004;Seddon et al 2004), and disease resistance (Coltman et al 1999).…”