Recent studies of parasitoid-host interactions have demonstrated that parasitoids and their hosts are geographically structured for traits such as virulence and encapsulation defenses, but no studies have yet compared the geographic structure of parasitoids and hosts using neutral genetic markers. Such studies of geographic structure are needed to evaluate the underlying geographic scale at which these interactions evolve and allow assessment of the relative effects of selection and gene flow on the geographic structure observed in traits under selection. We used sequence data from the mitochondrial DNA cytochrome oxidase I and II subunits to document and compare the geographic structures of the parasitoid Agathis thompsoni and its moth host Greya subalba. We also documented the geographic structure of G. enchrysa and compared it to the geographic structure of its parasitoid Agathis n. sp. The results demonstrated that parasitoids and their hosts may have incongruent patterns of geographic structure as assessed by molecular markers. As a consequence, the geographic scale at which the interaction evolves may be different for each species involved in the interaction. Depending on the interplay of selection and gene flow, there may not be a one-to-one correspondence of traits important in the interaction between parasitoids and their hosts at the level of local populations. The geographic structures of A. thompsoni and G. subalba and Agathis n. sp. and G. enchrysa provide further evidence of the potential importance of the formation of geographic mosaics in coevolving parasitoid-host interactions and evolving interactions in general.
Keywords: Cytochrome oxidase I and II; geographic structure; parasitoid-host interactions; phylogeography; population differentiation.
© 1999 The Society for the Study of Evolution.