Testing host associated differentiation on two parthenogenetic parasitoid species in a native forest system

High specialization on certain hosts can lead parasites to undergo differential selection and then sympatric speciation through host associated differentiation or HAD. Although HAD has been described to occur in some insect-plant communities in the wild, little is known about factors that determine it. It seems that factors such as the time of interaction between host and parasites and the presence of parthenogenesis may play a role in the likelihood of HAD to occur in a specific system. In particular, HAD should be more common in native species than in introduced species. Similarly, parthenogenetic species could be more prone to HAD than non parthenogenetic species. Further, HAD should be more likely in forest ecosystems due to the higher stability of these environments. In this study we have assessed HAD on two egg parasitoids species, Ooencyrtus pityocampae Mercet (Hymenoptera: Encyrtidae) and Baryscapus servadeii Domenichini (Hymenoptera: Eulophidae). These two species are both parthenogenetic. The former is a generalist and the latter a specialist parasitoid of one of the main European pine forest pests, the pine processionary moth, Thaumetopoea pityocampa Denis & Schiffermuller (Lepidoptera: Notodontidae) on its two main host plants in Italy (i.e., Pinus nigra and Pinus sylvestris). The present study used AFLP markers to determine if HAD is present on a native system involving a parthenogenetic parasitoid attacking a free feeding herbivore on two related tree species.