Abstract
Cleptoparasitic bees of the subgenus Stelis (Stelidomorpha) occur mainly in the Mediterranean and Middle East. In this study, we elevate Stelis aegyptiaca ssp. canaria Warncke, 1992 to species rank (S. canaria Warncke, 1992) and describe two new species, Stelis alainensis Kasparek sp. nov. and Stelis surica Kasparek sp. nov., both discovered in Oman and the United Arab Emirates. Morphological differences between these species and their closest relatives (S. aegyptiaca Radoszkowski, 1876, S. pentelica Mavromoustakis, 1963, and S. nasuta (Latreille, 1809)) are corroborated by genetic divergence in the mitochondrial COI barcode region, with Kimura 2-parameter (K2P) distances of 7.6-15.2%. A notable case is Stelis nasuta, which shows deep genetic subdivision into three clusters: (1) Iberian Peninsula and North Africa, (2) southeastern France, Italy, and the Balkans, (3) eastern Balkans, Turkey, and the Levant. Moderate genetic K2P distances of 2.9-3.3% complicated species delimitation. Analyses with ABGD, ASAP, bPTP, and RESL algorithms consistently supported recognition of these lineages as putative species. As multivariate analyses of 11 morphometric traits revealed no consistent diagnostic differences, we treat these lineages as phylospecies rather than formal taxa. Our findings demonstrate that bee diversity in the Palaearctic remains underestimated, and that expanded sampling and integrative approaches continue to reveal hidden lineages.