Towards new insights for Pityogenes chalcographus in Eurasia

During the last decades bark beetles have played an ecologically and economically important key role in forest management. Damages of these secondary forest pests often result from exceptional climatic events i.e. storms like those 1990 in Europe, causing the windthrow of about 32 million m3 of spruce. In this context, understanding the genetic structure, ecology and evolutionary history of these beetles is crucial for forest protection. The bark beetle Pityogenes chalcographus L. is regarded as a serious pest in European conifers forests, primarily on Picea abies, but it also attacks other Pinaceae species. Currently it is the target of several researches on ecology, genetic and phytosanitary aspects but some questions remained unclear. Up to now, P. chalcographus specimens have been investigated by applying mainly mitochondrial and nuclear single-nucleotide polymorphism markers. While mitochondrial markers gave a good representation of population structure, phylogeography and host influence, the nuclear ITS2 marker lacked resolution to address these questions. A significant differentiation of the species in six mitochondrial lineages was observed in Northern Europe, Central Europe, Apennine and Dinaric Alps, and no effect of host tree species could be detected at micro scale, results of its good abilities for host shifting and dispersion. Conversely, no obvious pattern of differentiation was highlighted with the nuclear ITS2 marker. P. chalcographus is described as a Palearctic species, yet all studies deal with European populations and very little is known about its distribution outside Europe. Investigation of microsatellite markers has allowed significant advances in molecular ecology, evolutionary biology and forest pest management. However, until few years ago, the potential benefits have been compromised by the tedious and expensive development of these markers. Next-generation sequencing technologies offer the potential for rapid and cost-effective development of microsatellite markers and hold particular promise for non-model organisms in ecology for which no reference genome exists. This valuable method makes marker detection easily accessible even for taxa where the isolation failed or was complicated. The focus of this proposed project shall be the phylogeographic investigation of P. chalcographus across multiple host taxa over a wide geographic range using microsatellite markers derived from next generation sequencing procedure. In doing so, the genetic variation among populations will be determined and the genetic structure, dispersal patterns and host specialization may be inferred and compared to the mitochondrial scheme. Moreover, the geographical distribution, host range and genetic variation of P. chalcographus populations in Siberia and Asia will be explored in order to gain new insights of the species biology and taxonomy. This study may provide critical information for both preventative and reactive forest management.