MITOCHONDRIAL DNA VARIATION IN THE PITCHER PLANT FLY SARCOPHAGA SARRACENIAE: EXPLORING POSSIBLE INFLUENCES OF HOST SPECIFICITY AND GEOGRAPHIC STRUCTURING

Abstract

North American pitcher plants (Sarracenia) are a recently evolved (~3 my) assemblage of 11 carnivorous species. Sarracenia pitchers also provide resources (food, shelter) for certain arthropods, including two genera of flesh flies (family Sarcophagidae) whose larvae develop within pitchers: Fletcherimyia, and a second, single species in the genus Sarcophaga (S. sarraceniae). Sarcophaga sarraceniae inhabits the entire geographic range of Sarracenia and appears to deposit larvae indiscriminately among various pitcher plant species whereas Fletcherimyia occupies smaller species ranges and shows pitcher host specificity. Is S. sarraceniae truly a pitcher generalist? To address this question, I examined mitochondrial DNA (mtDNA) variation in S. sarraceniae to test two hypotheses: 1) co-evolution—where observed mtDNA variation should be attributable to plant host fidelity, and 2) geography—where mtDNA variation should exhibit phylogeographic structure. I secured sequence data for the mitochondrial cytochrome oxidase 1 gene for 29 specimens representing 19 populations across the species range. Genetic variation was quite limited; it provided no support for the coevolution hypothesis but did show some phylogeographic structuring. These findings suggest that the symbiotic relationship between S. sarraceniae and Sarracenia may have been established fairly recently.