Factors determining the structure and diversity of parasitoid complexes in tephritid fruit flies.

The relative importance of phylogenetic affinity of hosts versus their ecological characteristics in determining the composition of their parasitoid complexes was examined using the parasitoid complexes of six species of frugivorous fruit flies from Central Europe. The hosts were four Rhagoletis and two other trypetine species, ranging in their relatedness from host races to members of different genera. They also differed in ecological characteristics, utilizing host plants of three different families, and developing either as pulp- or seedfeeders inside the host fruit. These features made it feasible to test the following pair of hypotheses. The ecological hypothesis predicts that ecological traits such as host-plant and fruit fly phenologies and host-fruit texture should be more important for the composition of parasitoid complexes than the taxonomic relatedness of the fly species. Assuming that ecological relationships do not parallel phylogenetic ones, the alternative phylogenetic hypothesis predicts the opposite. In fruit and soil samples, taken between 1983 and 1989, three guilds of parasitoids comprising 20 species were found: guild 1 - koinobiotic larval parasitoids (e.g. Opius spp., which attack the host larvae but develop inside the host puparia); guild 2 - idiobiotic larval parasitoids (e.g. Pteromalus spp., which consume the host larvae at once); and guild 3 - idiobiotic puparium parasitoids (e.g. Phygadeuon spp.). Although some results support the phylogenetic hypothesis, the majority of results support the ecological hypothesis.