One is a worldwide invader, the other never established in other continents: contrasted phylogeographic patterns of two congeneric Hylurgus conifer bark beetles

In the Western Palaearctic, the congeneric bark beetles Hylurgus ligniperda and Hylurgus micklitzi are developing on pine trees. Although H. ligniperda has a larger native range in Europe, both species often occur in sympatry in the Mediterranean Basin. They share rather similar life histories, thus providing an excellent model for comparative studies on species differentiation and ecological traits. Moreover, along with increasing human activities and international trade, H. ligniperda has invaded all continents, whereas H. micklitzi remains confined to the Mediterranean Basin. Our research utilised COI markers to assess the genetic diversity and structure, alongside the demographic history, of both species and revealed marked differences. H. micklitzi exhibited low genetic diversity and shallow population structures with restricted expansion. In contrast, H. ligniperda displayed a longer and more complex post-glacial evolutionary route with four distinct clades originating from separate glacial refugia, coupled with considerable genetic variability across Europe. Comparative analyses about the two species suggest that species traits, such as larger body size, increased voltinism, broader ecological niches and frequent introduction events may have helped the fast global invasion and spread of H. ligniperda over the past century.