The geographic structure of parasitoid-host interactions

Studies of species interactions have demonstrated that the geographic structure among populations of a species have a strong influence on the evolution of interactions. Studies of parasitoid-host interactions, in particular, have documented geographic structure in ecologically important traits such as parasitoid virulence and host encapsulation defense. This study examined whether geographic structure can also form in the searching behaviors of female parasitoids, whether the pattern observed in searching behavior is the same as the pattern of geographic structure as determined by neutral genetic markers, and whether parasitoids and their hosts have congruent patterns of geographic structure. Behavioral observations of females from four populations of a recently discovered parasitic wasp in the genus Agathis (Braconidae: Agathidinae) indicated that populations were geographically structured for female searching behavior. This pattern of geographic structure did not correspond to the pattern obtained from sequence data of the mitochondrial DNA cytochrome oxidase I and II subunits, suggesting that selected traits may sometimes have different patterns of geographic structure than neutral genetic markers. Sequence data from the same regions were used to compare the patterns of geographic structure of Agathis n. sp. and its moth host Greya enchrysa (Prodoxidae) and another species of Agathis, A. thompsoni and its moth host G. subalba. The data suggested that parasitoids and their hosts can have congruent and also incongruent patterns of geographic structure. Agathis thompsoni and G. subalba had congruent patterns, whereas Agathis n. sp. and G. enchrysa had incongruent patterns. Agathis n. sp. exhibited significant population subdivision over the same region in which G. enchrysa did not. Taken together, the results of this study indicate that parasitoids and their hosts may form groups of geographically structured populations, and the pattern of geographic structure may influence the evolution of parasitoid-host interactions.