Ecological interactions among species in communities are among the most important influences driving adaptive evolution and diversification. However, communities are not homogeneous, and for species with broad geographic ranges their ecological interactions can vary both temporally and geographically depending on the local community composition. Variation in community composition can produce variation in both the strength and nature of species interactions and so could minimize the likelihood of tight coevolution between species. Does temporal or geographic variation in the composition of communities influence the evolution of traits that determine outcome of species interactions? To begin to address this question, characterizing the patterns of geographic and temporal variation in the composition of communities is important for understanding the evolutionary outcome of species interactions. I carried out the first field survey of communities of frugivorous Drosophila species (Insecta: Diptera: Drosophilidae) and their Leptopilina parasitoids (Insecta: Hymenoptera: Figitidae). Fruit baits and yellow pan traps were used to collect insects two to three times a year encompassing their breeding season in seven locations along the east coast of North America, from New Hampshire to south Florida. Field samples were sorted to the species level and used to describe local host-parasitoid community structures.
Results/Conclusions
We found extensive seasonal and geographic variation in host-parasitoid community composition and relative densities of species across the range. There are 34 drosophilid species and 6 Leptopilina species (3 newly described) recorded in our field survey. Fly species diversity was highest in New Hampshire (Shannon-Wiener diversity 1.446) and South Florida had the lowest (Shannon-Wiener diversity 0.557). These two sample sites also had the highest community dissimilarity. For Leptopilina species, the highest species richness was in Maryland (5) and the lowest was in New Hampshire (1). As there is no identification system for Leptopilina in any part of the United States, we also provide an identification key of eastern North American species. This large collection of specimens also allowed us to identify inter- and intraspecific phenotypic variation and diagnostic characters for Leptopilina species. This study lays the groundwork for future research to understand how geographic and temporal variation in the biodiversity of communities influence the evolution of interacting species. Moreover, the Leptopilina identification key and routinely documented fruit pest Spotted Wing Drosophila (SWD; Drosophila suzukii) in our collections will also assist in the research of this recent invasive pest in the United States.