Complex postglacial history of the temperate bark beetle Tomicus piniperda L. (Coleoptera, Scolytinae).

Tomicus piniperda is an economically important pine bark beetle infesting European Pinus spp. stands. We sequenced and analyzed 797 bp of the mitochondrial genome from individuals obtained from 34 populations sampled throughout the European range. We obtained 36 haplotypes, from which a haplotype network was constructed. In the Iberian Peninsula, high-genetic variability was detected with numerous endemic haplotypes. In contrast, the other European populations were less diverse with a single haplotype predominating from the Pyrenees to Scandinavia. Nevertheless, even within Europe, a few populations showed significant amounts of diversity. Four groups were obtained by Spatial Analysis of Molecular Variance, illustrating the regional characteristics of the species. T. piniperda had multiple fragmented refugia in the Iberian Peninsula. These currently isolated populations only partly contributed to postglacial re-colonizations of Northern Europe during interglacials. Nevertheless, few long-range migration events up to Northern Europe were detected, mostly originating from the Pyrenees. In the rest of Europe, the phylogeographical patterns were unclear, because of repeated cycles of contraction and expansion. The genetic analysis showed one glacial refugium in North-Central Europe, whereas other refugia most likely occurred in the Southern Alps, Apennine and the Balkans. The phylogeographical pattern depicted here reflects partly the postglacial history of the beetles' main host tree P. sylvestris.