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Title: Estimating ecological and population genetic parameters in Myodes glareolus, a mammal with cryptic reproduction and dispersal
Author: Helyar, Sarah Jane
ISNI:       0000 0001 3552 4320
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2007
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S .J. Helyar; Estimating ecological and population genetic parameters in Myodes glareolus, a mammal with cryptic reproduction and dispersal A central theme in ecology is the determination of the factors that regulate population dynamics. For many years research has focused on systems regulated by predation, competition or resource Iimitatiofl, while the host parasite relationship wa~ considered to be neutral or benign, due to host-parasite co-evolution. However, in recent years there has been increasing recognition that parasites can have a key role in population dynamics, by influencing the key population parameters of reproduction and survival, and therefore having the potential to influence the population's intrinsic rate ofincrease. This study applies population genetics to host parasite ecology in order to determine how the endemic Cowpox virus interacts with and affects the host population processes of reproduction and dispersal in the bank vole (Myodes (= ClelhrionomY$) glareolus, Shreber 1780). This is a particUlarly challenging situation for determining parental relationships, as bank voles exhibit cryptic mating and maternal care, meaning that no information is available from behavioural observations to support the pedigree construction. Therefore a simulated population is first used to determine which software was most appropriate to use. A combination of parentage and sibship analyses is then used to maximise the information obtained on relationship structure. The fine scale population structure is also determined. Two events have been shown to cause variation in the levels of relatedness within a population, philopatry and founder events, and both of these are shown to be occurring in this population. This study demonstrates the occurrence of sex-biased dispersal using genetic techniques, so confirming a behavioural mechanism that is hard to identify via CMR studies due to the postnatal dispersal of this species. I also describe the fine scale population structure, and the seasonal fluctuations in this structure, with higher levels of structure evident during the summer than winter, which are determined by a combination of male biased dispersal and changes in population density. These analyses are then extended to consider how the population .genetics of the bank vole can contribute to our understanding of the bank vole-cowpox system. Two hypothesis are investigated; firstly to determine if there are patterns of infection that can be identified from the host genetics, and secondly to build on previous studies, by determining if the delay in the onset of breeding due to cowpox infection has an effect on the Lifetime Reproductive Success (LRS) of. the host. While no conclusive evidence was found for the transmission pathway, we do show that the delay in the onset of reproduction caused by cowpox infection has a major negative effect on LRS, reducing the number of an infected females' offspring by 30-100% compared to an uninfected female. Importantly, as cowpox prevalence increases with density in this species and populations with a high prevalence of cowpox are predicted to have reduced fecundity, cowpox virus infection therefore may be considerably influencing population dynamics.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available