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Title: Wolbachia infection and mating behaviour in the solitary sheet web spider, Pityohyphantes phrygianus
Author: Cotterill, Melanie Aimée
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2012
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Scandinavian populations of Pityohyphantes phrygianus have been observed to maintain a female biased sex ratio and exhibit a high infection prevalence of the maternally inherited bacteriumWolbachia. Previous research has suggested a role for female control in offspring sex ratio and that the direction of this relationship may be influenced by the Wolbachia infection status of the male (Gunnarsson et al. 2009). This study is the first to compare Scandinavian populations with a previously unstudied UK population. Analyses suggest that Wolbachia infection and reproductive behaviours are intrinsic to the species and are not seemingly the result of demography or localised environmental factors. No association was found between spider gender and Wolbachia infection, therefore Wolbachia is not acting through parthenogenesis induction or male- killing. The main focus of this project was to continue the study into female mating behaviour, to integrate detailed studies of male behaviour into the current literature, and to investigate the role of Wolbachia in influencing behaviour of both sexes. Results are in agreement with previous research indicating that female fitness is positively correlated with female position and, in addition, observed a positive correlation between size and fecundity. Interestingly, Wolbachia infected females appear to benefit from a significant size advantage over their uninfected cohorts. There is strong evidence that Wolbachia infection also influences male behaviour and, that male behaviour can direct female behaviour post-copulation. These results are unprecedented in spider-Wolbachia research. It is conceivable that Local Resource Competition operates within the population with larger, fitter, females producing more sons. The mechanism by which offspring sex ratio is distorted is likely to be female mediated, through processes of cryptic female choice. Within this population, Wolbachia acts as a beneficial symbiont, through increased fertilisation success as a consequence of an increase in female size and the potential for male infection status to increase female fertilisation success. This research identifies P. phrygianus as a biologically interesting system in which to study sex ratio theory and in a wider context contributes to the understanding of reproduction in spiders and the influence of maternally inherited bacteria.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available