Discrepant results obtained from phenotypic classification and genetic barcoding: A case study of the anthidiine bee Anthidium dalmaticum Mocsáry, 1884 (Megachilidae, Anthidiini)

The West Palaearctic wool carder bee Anthidium dalmaticum Mocsáry, 1884, is recognized in two subspecies: the nominate subspecies, widely distributed from the northern Adriatic Sea coasts to the Caspian Sea coastal areas, and A. d. ssp. syriacum Pérez, 1912, which has been regarded at times as distinct species and is found in the South Caucasus, the Levantine region and Iran. These two taxa are primarily distinguished by differences in colouration. In a genetic barcoding approach based on the sequence of the mitochondrial cytochrome c oxidase subunit 1 gene (COI), I was unable to differentiate between these two taxa. Additionally, a multivariate statistical analysis of nine body measurements did not reveal any significant morphometric differences between these two groups. However, a haplotype network analysis revealed that A. dalmaticum comprises three distinct evolutionary lineages. Of them, the Eurasian lineage covers most of the distribution range and includes members of both subspecies. The other two lineages are found in Iran and the Levant respectively, representing two independent evolutionary pathways. Notably, these two lineages exhibit significant genetic divergence, with each being more closely related to the Eurasian lineage than to each other. Based on these findings, it is concluded that the expansion of A. dalmaticum into the Iranian landmass and the Levant are two independent processes, which may have occurred in different phases of the climate oscillations between glaciations and warm cycles. The observed colour differences between the subspecies may be regarded as a convergent adaptation, possibly triggered by factors such as similar environmental conditions. Given that, on the one hand, the genetic lineages lack support from phenotypic traits and, on the other hand, the colour forms are not corroborated by genetic data, the available evidence is not yet regarded as sufficient to classify these forms as distinct taxonomic units. It is suggested to treat A. dalmaticum ssp. syriacum as a synonym of nominate Anthidium dalmaticum.