| dc.description.abstract | In recent years there has been a global trend in declines of pollinator species primarily due to anthropogenic stressors, including habitat fragmentation and land-use change resulting from agricultural intensification. The subsequent loss of foraging plants via this process creates habitat ‘islands’, causing genetic isolation similar to that found on geographic islands. Isolated populations are at a much greater risk of inbreeding and reduced genetic diversity, which in turn increases their susceptibility to disease. To reduce the fragmentation of wildlife populations, the EU introduced Agri-environmental schemes (AES) which provide mitigation methods including offers of financial aid to farmers planting wild flower margins. This thesis compared two wild bumblebee species between island and mainland sites in the UK and France to assess the impact of geographic isolation on populations. This thesis also sampled four bumblebee species in sites with different levels of AES in the UK, to assess the efficacy of the schemes in terms of promoting genetic diversity and analyse relationships between heterozygosity and disease. By using genetic techniques to estimate the diversity, structuring and population size of each species, comparisons between different environment types were made. Molecular analysis found significant structuring in Bombus pascuorum (θ = 0.122) populations across the UK and French populations. Within B. pascuorum populations, there was found to be a higher prevalence of the gut trypanosome Crithidia bombi in populations with reduced heterozygosity. Molecular analysis of the agri-environmental sites found a positive relationship between floral diversity and the heterozygosity of the population, and a large proportion of genetically similar sister pairs were sampled within these sites. 4 The overall conclusions from the research presented in this thesis are that to sustain wild pollinator numbers, further development of agri-environmental schemes is required with a focus on increasing floral diversity. Even with low intensive sampling effort sister pairs are likely, which can impact the results of epidemiological studies of haplodiploid species. Furthermore, the genetic analysis presented here suggests a strong link between population isolation and disease prevalence, thus isolated populations are at greater risk of extinction unless intervention occurs. | en_GB |
