Traditional and geometric morphometric analyses reveal homogeneity in European Scutacarus acarorum Goeze, 1780 populations (Acari: Scutacaridae: Heterostigmatina)

The mite Scutacarus acarorum (Scutacaridae, Heterostigmatina) is one of the dominant bumblebee inquilines in the Holarctic. The wide distribution and the host generalist behaviour of S. acarorum suggest that it could be a group of multiple cryptic species. European S. acarorum populations and a small population from New York were studied using traditional and geometric morphometric methods to detect possible geographical or host-dependent variation. The analyses revealed homogeneity of all populations, suggesting that the species experienced a bottleneck during the last ice age and that gene flow between the populations is maintained. High variability within populations indicates a high genetic diversity. No host-related morphological differences were detected, suggesting that S. acarorum is a true generalist. Fresh mite samples from locations all over the Holarctic are needed to draw further conclusions on the species' phylogeography and also on its population genetic structure.