South American leaf-cutter bees (Genus Megachile) of the subgenera Rhyssomegachile and Zonomegachile, with two new subgenera (Hymenoptera: Megachilidae)

Authors: GONZALEZ, VICTOR - Utah State University; Griswold, Terry; ENGEL, MICHAEL - Utah State University

Submitted to: American Museum Novitates
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2018
Publication Date: 11/2/2018
Citation: Gonzalez, V.H., Griswold, T.L., Engel, M.S. 2018. South American leaf-cutter bees (Genus Megachile) of the subgenera Rhyssomegachile and Zonomegachile, with two new subgenera (Hymenoptera: Megachilidae). American Museum Novitates. 425:1-74. https://doi.org/10.1206/00030090-425.1.1.
DOI: https://doi.org/10.1206/00030090-425.1.1

Interpretive Summary: One of the most common and varied groups of bee pollinators are the leaf-cutter bees (genus Megachile), found across the globe in both temperate and tropical environments. Unfortunately, identifying species of leaf-cutter bees is difficult not only because there are so many species, but also because many species have not yet been named or are poorly known. Some species are known only from a single specimen or from only one sex, and identification keys are not available for many groups of leaf-cutters. This research creates an illustrated identification key to all the leaf-cutter bee groups in North and South America that will aid researchers in ecology, biodiversity and conservation to identify these important pollinators. Several new species are also described from South America and two distinctive groups are given new subgeneric names.

Technical Abstract: Leaf-cutter bees (genus Megachile Latreille) are among the most common and diverse group of bees. However, the identity and taxonomic placement of many species are problematic and species identification is often difficult. Some species are known only from a single specimen or from one of the sexes, and identification keys are not available for many groups. We address these taxonomic issues for the subgenera Rhyssomegachile Mitchell and Zonomegachile Mitchell, two poorly known South American lineages of leaf-cutter bees. We provide comparative diagnoses, redescriptions, illustrated identification keys, new geographical records, and, where needed, designate neotypes for Megachile cara Mitchell, M. stabilis Mitchell, M. reliqua Mitchell, and M. turbulenta Mitchell. We resurrect M. tricosa Cockerell from synonymy with M. urbana Smith, and synonymize M. turbulenta under M. tricosa. We recognize four species in Rhyssomegachile and eight species in Zonomegachile. In the latter subgenus, we revalidate M. reliqua from synonymy with M. moderata and propose the following four new species: Megachile kalina, new species, from French Guiana; M. durantae, new species, from Rondônia, Brazil; M. paisa, new species, from Antioquia, Colombia; and M. uncinosa, new species, from Catamarca, Argentina. We confirm sex associations in Zonomegachile and describe its nest for the first time. Megachile tricosa, M. ardua Mitchell, and M. tacanensis Moure, currently assigned to Rhyssomegachile, exhibit morphological features that do not fit any of the known subgenera. Thus, we use a cladistic analysis to explore their phylogenetic relationships and establish two new subgenera for these species: Aporochile Gonzalez and Engel, new subgenus, for M. tricosa and Chalepochile Gonzalez and Engel, new subgenus, for the remaining two species. We provide an updated key to the subgenera of Megachile s.l. of the Western Hemisphere.