Why make it easy when you can make it difficult? the nigritus group as example of the current challenges in the traditional taxonomy of the bee genus Hylaeus Fabricius (Apoidea: Colletidae)

Journal of Natural History, vol. 60, pp. 1799–1897

Abstract

The genus Hylaeus Fabricius is one of the most diverse and taxonomically challenging bee genera in the Palaearctic region, with a confused taxonomy and unclear supraspecific classification. The nigritus species group, currently assigned to the subgenus Hylaeus, was previously considered to comprise 13 species, primarily distributed across Asia. Despite a recent revision, reliable identification of the group and its constituent species has remained difficult. We present a comprehensive revision of the group based on detailed morphological study combined with DNA barcoding. Our review revealed that several taxa had been described or interpreted under poorly defined species concepts, leading to frequent misassociation of sexes, taxonomic inflation, misinterpretation of historical type material and arbitrary delimitation of both the species group and the associated subgenus. The subgenus Patagiata Blüthgen is synonymised with the subgenus Hylaeus because its constituent species lack shared synapomorphies. We provide a revised definition of the nigritus group based on morphological characters and supported by a CO1 phylogeny of the group. It now includes only eight species, including three new species described herein: Hylaeus malitiosus Le Divelec, sp. n. (France), H. ludificator Le Divelec, sp. n. (France and Spain) and H. paimoni Le Divelec, sp. n. (Armenia and Iran). Species previously associated with the nigritus group s.l. but excluded here are also revised. Two species are reinstated to species rank: H. jugorum Morawitz stat. rev. (= H. mellon Dathe and Proshchalykin syn. n.) and H. peregrinus Dathe stat. rev. In total, 11 additional new synonymies are established. An identification key to the nigritus group s.str. is provided, along with redescriptions and comparative diagnoses for the 10 species previously associated with the group s.l. This revision clarifies the taxonomy of several problematic Asiatic Hylaeus species and illustrates how insufficiently rigorous taxonomic practices can propagate errors across species delimitation, identification, classification and biodiversity data.

Authors 7

1. Romain Le Divelec corresponding
   Affiliation as printed

   Research Institute for Biosciences

2. Christian Schmid‐Egger
   Affiliation as printed

   Independent Researcher

3. Daniel Benda

   Charles University · National Museum

   Affiliation as printed

   Charles University

   National Museum of the Czech Republic

4. Denis Michez
   Affiliation as printed

   Research Institute for Biosciences

5. Kobe Janssen
   Affiliation as printed

   Independent Researcher

6. Villu Soon

   University of Tartu

   Affiliation as printed

   University of Tartu

7. Thomas James Wood Aachen Naturalis Biodiversity Center

   Naturalis Biodiversity Center

   Affiliation as printed

   Naturalis Biodiversity Center