Genetic diversity and invasion history of the European subterranean termite Reticulitermes urbis (Blattodea, Termitoidae, Rhinotermitidae)

Biological invasions are among key factors of ecological changes, and social insects appear as highly successful invasive animals. Subterranean termites of the holarctic genus Reticulitermes are present in Europe with six native and one invasive (the nearctic R. flavipes) species. The species R. urbis shows a disjunct distribution in the Western Balkans, Eastern Italy and Southern France. Previous molecular and population genetics data suggested that the taxon originated from the Balkans, and that Italian and French populations are invasive, but it is still unknown how many introduction events occurred and from which Balkan source populations. To address these questions, a population genetics analysis was performed on a larger sampling than previous studies, using mitochondrial cytochrome oxidase II and 6 microsatellite markers on 47 colonies collected across the whole distribution area. Mitochondrial analysis confirmed the presence of two major lineages where colonies from Balkans, Italy, and France intermingle. Similarly, microsatellite loci analysis indicated the presence of two genetic clusters, though not corresponding to the two mitochondrial clades, each including colonies from the three sampled areas and with individuals showing mixed cluster membership. Overall, French and Italian populations showed indications of bottleneck (reduced genetic diversity and change of allele frequencies) and do not appear genetically differentiated from the Balkan population. Results presented here support a history of multiple introductions in Italy and France, in a scenario consistent with continuous exchanges between native and invasive areas, as expected along human trades routes.