Term of Award

Spring 2014

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Biology

Committee Chair

Scott Harrison

Committee Member 1

Edward Mondor

Committee Member 2

Kelly McLain

Abstract

Wolbachia was recently identified in the Brown Widow Spider (Latrodectus geometricus). This symbiont has not previously been found in this genus, therefore the consequences on the host’s population dynamics are unknown. The frequency of endosymbiont infection can provide insight into the population dynamics of the host as this bacteria is known to alter host life history. In my 1st chapter I determine the prevalence of Wolbachia pipentis infection in in the Brown Widow Spider (Latrodectus geometricus) from five locations in the Southeastern United States. Infection frequency differed significantly among sampling locations, ranging from 20% to 92%. These results suggest that the s­­­train is not an obligate symbiont and does not provide a strong fitness benefit to the spider. The observed distribution pattern also suggests recent founder events and possibly limited gene flow among sampled locations as we would expect similar infection frequencies in populations with high gene flow. Wolbachia is known to alter arthropod life history patterns (e.g., male-killing, feminization, induced parthenogenesis, nutrient acquisition, etc.). As this symbiont has not previously been found in the genus Latrodectus, the consequences on the spider’s life history patterns are unknown. In the 2nd chapter, I examine the effects of infection on the spider’s reproduction (sex ratio, clutch size, egg size, and egg mass) and juvenile development time. No significant difference in clutch sex ratio, egg number, egg size, egg mass, or development time was found between infected and uninfected females. These results suggest that the strain is not an obligate symbiont nor does it alter the reproductive biology of the spider, as it does in most species. The lack of effect on the host suggests infection is either: i) neutral, and remains in the population by complete maternal transmission or has reached an equilibrium, or ii) affects a trait that was not analyzed in this study.

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