Molecular markers reveal strong geographic, but not host associated, genetic differentiation inAphidius transcaspicus, a parasitoid of the aphid genusHyalopterus

Host plant associated genetic differentiation is a common phenomenon in phytophagous insects, but the degree to which such associations sequentially drive diversification at higher trophic levels is not as well understood. A recent study examining neutral molecular markers inHyalopterusaphids revealed that genetic structure in this genus is strongly determined by primary host plant use (Prunusspp.). In this paper, we take a similar approach to determine whether this host plant specificity has affected genetic structure in the parasitoidAphidius transcaspicus, an important natural enemy ofHyalopterusspp. in the Mediterranean. Mitochondrial DNA (428 bp) and seven microsatellite loci were examined in parasitoids collected from aphid populations on almond, apricot, peach and plum trees from Spain and Greece. In contrast to the previous findings forHyalopterusfrom the same regions, here we find no evidence for host associated diversification inA. transcaspicusat the species level or below, though geographic structure between regional populations is exceptionally high. These findings have several implications for our understanding of the ecology and evolution ofA. transcaspicusas well as for its use as a biological control agent forHyalopterus, suggesting that a consideration of host plant specificity may be less critical than factors such as climatic suitability or geographic origins of invasive populations.