| Summary: | The European water vole (Arvicola amphibius) has undergone widespread declines across much of the UK and a major consideration for their future conservation is facilitating the admixture of individuals in modified landscapes to promote population growth, restore geographical distribution and ensure long term viability. However implementing remedial management strategies for these purposes requires knowledge of how populations are affected by, and respond to, fragmented and perceptively hostile landscapes. This thesis uses non-invasive genetic tools in conjunction with a live capture study to investigate the population structure, genetic variation and social systems of both natural and reintroduced water vole populations living within modified landscapes in southeastern England. In particular this research determines; a) whether non-invasive hair capture tubes are effective at collecting samples for genetic monitoring of water voles; b) whether there is a quantifiable difference in the demographic performance (survival, recruitment, population growth), neutral genetic variation and kin structure of populations occupying linear habitats compared to unmodified non-linear wetland habitats and c) identify the spatial pattern of variation in microsatellite and mitochondrial DNA amongst water vole populations to investigate natural and human mediated factors effecting historical and contemporary distribution. Non-invasive hair capture tubes proved to be a successful and efficient method for obtaining hair samples from wild populations of water voles with one genetic sample taking 0.53 man hours and costing £0.80, which was four times more efficient and 13 times more cost effective than live capture methods. However, DNA degradation, low quantities of DNA template and small sample sizes were identified as limiting factors when applying this method to genetic studies on water voles. Different patterns in demography and kin structure of water voles were observed between populations occupying linear and non-linear wetlands. Water voles in linear wetlands showed higher overall survival and dispersal of young, but were characterised by a significantly lower proportion of breeding females in spring which resulted in higher levels of female philopatry and incidents of inbreeding. Populations occupying non-linear wetlands were comprised of more breeding females in spring which had a positive influence on population growth. There was also evidence to suggest that when the abundance of overwintered females was high, the sexual maturation of female young was suppressed which concurred with fewer breeding female relatives being observed after the breeding season in populations occupying non-linear habitat types. Tolerance between female kin was reduced in both habitats types with increasing abundance of voles and no spatial avoidance between opposite sex mates was observed. Genetic diversity was similar between populations occupying linear and non-linear wetlands and significant temporal variation in genetic composition was observed, particularly in linear wetlands, suggesting a high turnover of individuals. Between populations, genetic variance at microsatellite loci was partitioned amongst river catchments, which concurred with patterns in mitochondrial variation across southeast England. Reintroduced populations exhibited significantly higher genetic diversity in terms of heterozygosity and allelic richness, however spatial analyses across the study sites suggest that reintroductions have homogenised the genetic variation at microsatellite loci and evidence of captive breeding between divergent lineages that have no geographical affiliation to the study area highlight that reintroductions can contribute to the loss of genetic heritage and diversity.
|
|---|
