The ecology and population genetics of introduced deer species

Abstract

Deer have been introduced outside their native ranges numerous times worldwide, causing significant economic and environmental impacts. The scale of problems caused by some introduced deer species is expected to increase, while others are relatively harmless and may be important for conservation as their numbers decline in native regions. This thesis examines the factors promoting invasion in non-native deer, and investigates the population genetics of two deer species introduced to Great Britain. Factors hypothesised to predict invasion success were tested using a comparative analysis of the outcomes of introductions of non-native deer populations. Two modelling approaches were taken to account for confounding effects in species-level and population-level analyses, and different factors were found to explain success at different stages of the invasion process. Populations of roe deer expanding from refugia and reintroductions were examined, and differences in genetic diversity between core and peripheral populations, alongside a decline in diversity with rate of expansion from the core were found. High levels of differentiation between and among core and peripheral populations suggest that genetic drift is the major factor causing these patterns. Using a genome scan of British and European roe deer, loci potentially under selection were identified. Association between some of these loci and environmental variables suggests that climatic extremes may have a role in exerting selective pressures on roe populations. The Chinese water deer is severely declining in range and number in its native habitat, but rapidly expanding after being introduced to Great Britain. Relatively high levels of diversity in native Chinese populations, and significant differentiation between the Chinese and British populations were found. The source population of the British deer is likely to be extinct, and the level of genetic structuring indicates that conserving populations across both ranges is important to maintaining their diversity.