Taxonomic studies of western North American Lasioglossum (Hemihalictus) and a problematic L. (Sphecodogastra) species complex

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Hettiarachchi, Thilina
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Sweat bees in the cosmopolitan genus Lasioglossum are some of the most diverse and commonly collected bees in terrestrial ecosystems. Lasioglossum is made up of several difficult to define subgenera including L. (Hemihalictus) and L. (Sphecodogastra). These two subgenera have never been completely revised in western North America. Taxonomic studies of western Lasioglossum were conducted to clarify subgeneric and species limits. A problematic species complex within L. (Sphecodogastra) was described, which created challenges for subgeneric diagnostics. An improved subgeneric diagnosis was developed for L. (Sphecodogastra) along with a revised key to Lasioglossum subgenera in North America. Then, a review of western Lasioglossum (Hemihalictus) was conducted. The species delimitation process employed an integrated approach, following morphological and geographical data to delineate species boundaries. Morphometric analysis was used for species in the L. (Sphecodogastra) iridescens and L. (Hemihalictus) arizonense groups, using linear discriminant analysis and partitioning around medioids. Three new L. (Sphecodogastra) were described: L. iridescens, L. dilisena, and L. silveirai. Twenty five species of L. (Hemihalictus) were treated, five of which are described as new: L. angustoides sp. nov., L. engleri sp. nov., L. pathiranae sp. nov., L. opata sp. nov., and L. tomentosum sp. nov. Two Palaearctic species are documented in North America: L. villosulum (Kirby) and L. buccale (Pérez). The male of L. subobscurum (Cockerell) is described for the first time. Lasioglossum vanduzeei (Sandhouse & Cockerell) is resurrected from synonymy with L. arizonense. Lasioglossum aspilurum (Cockerell) is considered a senior subjective synonym of Halictus humboldtensis Michener. Six western Nearctic species in the L. nitidiusculum species-group are included in two species complexes: L. ruficorne and L. diatretum species complexes, which likely include unverified synonymies.
Apoidea, classification, new species, Taxonomy, Lasioglossum