Host associated differentiation in indigenous tree species

Host Associated Differentiation (HAD) is the formation of genetically distinct host associated populations favored by ecological isolation and natural selection. One of the genotypic signatures of HAD is that populations on the same type of host do not exhibit differentiation across space but do exhibit differentiation when found on different host types in sympatry. HAD, as a mechanism promoting sympatric speciation, has been invoked to explain the enormous diversity of phytophagous and parasitic insects. While HAD has been well documented in a few model systems, we know very little about the factors that might promote it. Such factors could include concealed vs. exposed mode of feeding, parthenogenetic vs. non-parthenogenetic reproduction, and the duration of the interaction between insects and their hosts (i.e. native vs. introduced). Being able to better predict HAD might have important implications for biological control. For example, identification and introduction of putative biological control agents may need to take into account host-plant species as well as herbivore host species. We believe hickories of the genus Carya and their associated insect fauna provide an ideal model system for testing the prevalence of HAD in a diverse community of insects at multiple trophic levels. Preliminary amplified fragment length polymorphism (AFLP) data of the pecan bud moth Gretchena bolliana Slingerland (Lepidoptera: Tortricidae) suggest that HAD is not present in this native non-parthenogenetic herbivore on two of its native host-plant species.