Genetics and genomics of pine processionary moths and their parasitoids

The pine processionary moth (Thaumetopoea spp.), an important defoliator of Pinus spp. in the Mediterranean area, is recently expanding its range in response to climate change and anthropogenic factors. Therefore it's important to outline the way in which this pest can colonize new areas, and to do this molecular markers seem to be the most suitable tools. In the introduction I present some of the molecular markers used in the last years to study ecological and evolutionary problems related to insects. The main aim of my work was to analyze the genetic variability of pine processionary moth in its present range and so to try to reconstruct the recent and past colonization history of this pest. Secondly, another goal was to characterize the genetic structure of pine processionary moth parasitoids to better understand the factors involved in their differentiation such as in tracking their host on different pine species. In the first study I extended a work already begun on the population genetic of pine processionary moth to the populations of the Near East. The main issue of this study was to understand the origin of population attacking the Israel pine plantations and in second place to genetically characterize all the populations in the range. Moreover, this study shows the utility of the use of both nuclear and mitochondrial markers for the different information they can yield. In this case they permitted to track a gender-related dispersal, which could be important to maintain genetic variability in expansion areas. In the second study, I contributed to outline the genetic structure of pine processionary moth in the whole range. Through the mitochondrial markers used in the previous studies it was possible to define the main events occurred to this species in the past, identifying glacial refugia and the main splitting events among the different lineages. In northern Africa, a new unexpected genetic clade was found analyzing populations that were previously considered, on a morphological base, to belong to a subspecies of the two already described pine processionary moth species. In the third study, I contributed to the sequencing of the entire mitochondrial genome of Ochrogaster lunifer, an Australian species belonging to the same subfamily of the pine processionary moth. This study, besides to represent the first step to have insights into the taxonomy of the family, gave useful information about the best markers to be used in population genetic studies on Lepidoptera. In the fourth study, I dealt with the population genetic of two egg parasitoid species of the pine processionary moth: the specialist Baryscapus servadeii and the generalist Ooencyrtus pityocampae. The main goal of this study was to test the presence of a host plant association in these two parasitoids and to compare the genetic patterns of a specialist and a generalist. In the specialist parasitoid populations analyzed it seems to be present a genotype mostly associated with the host plant. Moreover, unlike the generalist, the specialist doesn’t show to have a genetic pattern spatially structured. This could be related to a higher mobility of the specialist, and hence to its strategy in finding hosts. These findings provide useful information to predict the behavior of parasitoids in expanding areas. On the whole, the four contributions provide suggestions for the range wide management of the pest, and insights into the evolutionary history of the group, including projections on the potential for adaptation to ongoing climate change.