Host associated differentiation in insects feeding on native tree species

Abstract: 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). 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. Using amplified fragment length polymorphism (AFLP) we have found no evidence of HAD in the non-parthenogenetic pecan bud moth (Gretchena bolliana). In contrast, HAD has been found in the parthenogenetic yellow pecan aphid (Monelliopsis pecanis). The role of parthenogenesis in mediating HAD is discussed.

Keywords: reproductive isolation, neutral molecular markers, plant-insect interactions