Phylogeography of Hepialus humuli (L.) (Lepidoptera: Hepialidae) in Europe: short distance vs. large scale postglacial expansions from multiple Alpine refugia and taxonomic implications

We explore the phylogeography of the common ghost moth, Hepialus humuli (Linnaeus) in Europe based on 1451 bp Cytochromeoxydase Subunit 1 (COI) mtDNA and 617 bp Ribosomal protein Subunit 5 (RpS5) ntDNA with special focus on populations in the Alps and surrounding regions, as well as northern Europe. While RpS5 fails to recover any phylogeographic signal, COI reveals a remarkable pattern with central European populations separated in four well-defined groups. The most divergent group is restricted to northern Italy and southern Austria and geographically isolated from the others; one group is found only in the central-northern region south of Lake Constance (Liechtenstein, western Austria) and co-occurs with the two other groups, from north-eastern Alps and north-western Alps respectively. We conclude that the southern and central groups are relicts from a previous Pleistocene glacial maximum, whereas the two latter groups were isolated during the last glacial maximum in a western and an eastern refugium respectively, the exact extends of these refugia are uncertain. The central group has subsequently interbred with the two other northern groups and probably only exists today as ancient mtDNA haplotypes. The north-western and north-eastern groups have spread considerably and overlap over a large part of their range in the Alps and surrounding areas. Following the last glacial maximum, the north-western group spread into western Europe as far as Normandy, but the English Channel has apparently acted as a dispersal barrier. The north-eastern group spread into eastern and northern Europe, including Scandinavia, and possibly into the Balkans as well. The British Isles as well as the North Atlantic islands groups, the Faroese and Shetlands were colonised from southern Scandinavia or northern Germany, likely via Doggerland. Despite the deep divergence in mtDNA between the populations in Italy and southern Austria, and the remaining populations, there are no consistent morphological differences, and we conclude that there is no evidence that the southern populations should be considered a separate species. Although the populations in the Shetland and Faroese islands are phenotypically distinct from most other populations, we find no genetic or genitalia morphological differences between these populations and the rest. We therefore conclude that they display what can be termed cryptic genetic homogeneity. As the phenotypic variation is not unique to these populations either, we synonymise the North Atlantic subspecies H. humuli thulensis Newman syn.n. with H. humuli humuli.