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Title: Monitoring population size, structure and change in Bechstein's bat (Myotis bechsteinii) : combined approaches using molecular and landscape ecology
Author: Wright, Patrick
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2018
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The Bechstein’s bat, Myotis bechsteinii, is known as one of Britain’s most elusive mammals. Critical information on the species is lacking, hindering evidence-based conservation and management in a human-dominated landscape. In this thesis, I used a combination of molecular and landscape approaches to assess the genetic health and population genetic structure of M. bechsteinii and understand how the British landscape affects the species habitat and its connectivity. I also aimed to develop new molecular tools, such as non-invasive genetic sampling and molecular ageing, which could then be used to better monitor the species. Data from nuclear markers (microsatellites) showed high levels of genetic diversity and little inbreeding across the species range, though genetic diversity was slightly lower in Britain than in mainland Europe. Bayesian and spatial Principal Components (sPCA) analysis showed a clear separation between British and European populations. This analysis also revealed that in Europe the Italian population south of the Alps was found to constitute a different group from other sites. In Britain, there was genetic structuring between the northern and southern part of the species range. Despite there being little genetic divergence in mitochondrial DNA (mtDNA) sequences throughout most of Europe, the mtDNA patterns in Britain confirmed this separation of northern and southern populations. Such genetic structuring within Britain — in the absence of any obvious physical barriers — suggested that other features such as landuse may limit gene-flow. To better understand how the species interacts with 4 the British landscape, I used a landscape genetic approach, habitat suitability modelling using presence-only data and a landscape connectivity analysis. The negative association of M. bechsteinii presence with distance from woodland was identified as the main variable determining habitat suitability, while the landscape genetics results highlighted the importance of woodlands for gene flow. M. bechsteinii habitat was highly fragmented and only showed good connectivity if the species was able to disperse over 5,000 m. These results subsequently highlight the importance of woodlands not only for providing suitable habitat, but also in maintaining genetic connectivity between populations. Then, I investigated the use of non-invasive capture-mark-recapture (CMR) and demographic history models to estimate the population size and changes of M. bechsteinii. Bat droppings were collected below roosting sites of a single colony. After species identification, the 123 droppings belonging to M. bechsteinii were genotyped at nine DNA microsatellite loci in order to differentiate all individuals. All microsatellites showed very low amplification rates indicating low quality samples. However, at a larger scale, the use of population demographic models to assess effective population size variation using a dataset of 260 bats of the British population gave an estimate of the effective population size of 6,569 (CI: 5,307-8,006) and suggested that the British population of Myotis bechsteinii is stable and possibly expanding. Finally, I developed an epigenetic assay to estimate the age of individual bats. For this, I measured DNA methylation on bats of known age at seven CpG sites from three genes. All CpG sites from the tested genes showed a significant relationship between DNA methylation and age and provided reliable age estimates. 5 The findings presented in this thesis show that despite exhibiting high levels of genetic diversity throughout its range, the genetic structure, habitat and connectivity of M. bechsteinii populations is highly influenced by woodlands. It also offers a novel method to monitor the species by developing an assay which can provide information on the age structure of an entire colony from a single sampling session. Such approaches are much needed in the field of conservation and could in the future help preserve a wider range of species.
Supervisor: Mathews, Fiona ; Hamilton, Patrick B. ; Schofield, Henry ; Wilson, Robert Sponsor: Vincent Wildlife Trust ; Woodland Trust ; People's Trust for Endangered Species
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Wildlife Conservation ; Conservation Genetics ; Bats