The evolutionary ecology of resistance to bacterial infection in natural populations of Drosophila melanogaster
Corby-Harris, Vanessa Louise
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Parasites are often unevenly distributed across host populations. Part of this variation in parasite prevalence is likely due to variation in the hostÕs ability to resist infection. Such variation depends on both evolutionary and ecological factors. The overall purpose of this work is to understand the evolutionary and ecological forces that maintain variation for resistance within and across naturally isolated host populations of the fruit fly, Drosophila melanogaster. Through the work presented here, I characterize variation for host fitness following bacterial infection within and among D. melanogaster host populations. I then seek to determine why such variation exists by testing two hypotheses. First, I test whether genetic variation for resistance within host populations is due to tradeoffs between resistance and fitness in the absence of infection. Second, I determine whether ambient temperature and the number of bacteria co-occurring with D. melanogaster hosts shape among-population differences in resistance to a novel infection. Overall, these experiments address important unanswered questions regarding the evolutionary ecology of resistance in natural D. melanogaster populations. Further, these results provide key insights into the natural history of D. melanogaster-bacteria interactions, which will motivate ecologically relevant laboratory models of insect-bacteria interactions in this experimentally tractable system.