Genetic and multivariate morphometric analyses unveil cryptic diversity in sympatric populations of the Mediterranean wool carder bee, identified as Anthidium undulatum Dours, 1873 (Hymenoptera: Megachilidae: Anthidiini)

The distribution of the anthidiine bee identified as Anthidium undulatum Dours, 1873 extends from the French Mediterranean coastal region across the Adriatic coast and the eastern Mediterranean to the Caucasus and Iran. Examination of the DNA sequence of the mitochondrial COI gene (“ barcoding unit ”) of 25 specimens from throughout the distributional range revealed the existence of three distinct clades, which are clearly separated with bootstrap values of 99 % and 100 % in a Maximum Likelihood Analysis.

The genetic distance between these groups ranged from 2.6 to 5.0 %, while the intra-group distance did not exceed 0.42 %. Two of these clades were found to occur in the same habitat in Lebanon. These three clades also differ in some phenotypic color traits, which, however, are not always fully diagnostic.

Despite this, a morphometric analysis of six parameters of the head and wings of the males showed that the three genetic clades also form distinct clusters in a Discriminant Function Analysis. The consistent results of the genetic and morphometric analyses, together with the co-existence of two of the three groups, support the recognition of these groups as distinct species. The three taxa recognized at the species level are: A. undulatum Dours, 1873, which has a wide distribution in the Mediterranean and extends eastwards to Iran; A. wahrmani Mavromoustakis, 1948 stat. nov., which is found in the southern Levant; and A. libanicum Kasparek sp. nov., which is known only from Lebanon, and where it seems to be endemic.

The results confirm the high diversity of anthidiine bees in the eastern Mediterranean and indicate that the species richness may be much higher than currently known. The sympatric occurrence of genetically and morphometrically distinct forms within the same habitat is considered strong evidence that these are distinct cryptic species, rather than variations arising from local geographic or environmental adaptations.