Mitochondrial DNA variation of Drosophila obscura (Diptera: Drosophilidae) across Europe

Drosophila obscura is a common fruit fl y that inhabits the temperate forests of Europe. While it is abundant in the north compared to other Drosophila, its density decreases southwards, where it is gradually replaced by other Drosophila species. This study describes variation in the mitochondrial Cyt b gene of D. obscura from several European populations. We observed a large number of haplotypes, together with the structuring of genetic variation. Genetic variation is higher in the west where O1 and related divergent haplotypes dominate. In the east, the O2 haplotype is most frequent, together with haplotypes that recently arose from it. In the central part of the species range, both O1 and O2 are equally present, along with many others. These data reveal signs of population expansions that probably happened earlier in the west, and more recently in the east. Though our conclusions are based on only one genetic marker, limiting the power of the analysis, the results imply either postglacial expansion from two unique sources or, more likely, eastwards stepping-stone expansion. This study adds important information on genetic variation and phylogeography to the obscure biology of D. obscura, a species that has the potential to become an interesting model in evolutionary biology and conservation genetics. * Current address: College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK; email: M.A.Wallace@exeter.ac.uk INTRODUCTION Drosophila obscura, the nominate species of the obscura group, is a Palearctic fruit fl y whose distribution extends from Southern Europe to the central Fennoscandia, and from Western Europe to central Asia (Lakovaara & Saura, 1971; Brehm & Krimbas, 1991). In Europe, its relative abundance decreases from north to south (Brehm & Krimbas, 1991). In southern Finland, it is the most abundant Drosophila species (Lakovaara & Saura, 1971). Along with D. subobscura, D. obscura is the one of the two most common Drosophila species in Great Britain, although D. subobscura outnumbers it during most months (Shorrocks, 1975; Begon, 1978). In the Central Balkans, among obscura group species, it is much less abundant than D. subobscura (Stanić et al., 2002; Pavković-Lučić et al., 2012), but is readily collected at higher altitudes (long-term observaEur. J. Entomol. 119: 99–110, 2022 doi: 10.14411/eje.2022.011