Phylogeny and subgeneric reclassification of Lasioglossum (Hymenoptera: Halictidae) based on ultraconserved elements

The large and diverse sweat bee genus Lasioglossum contains over 80 genus-group names whose status and limits are, in many cases, contentious or uncertain. The exact number of these names considered valid subgenera is difficult to determine because the information is scattered among various taxonomic papers and varies by author and time period. Some systematic confusion is attributable to the lack of a sufficiently robust and inclusive phylogeny, but even prior phylogenies based on four or fewer genes and limited taxon sampling agree on certain problems that have still not been fully resolved. Here we present the most comprehensive phylogeny of Lasioglossum to date, including 150 species in 24/32 genusgroups currently recognized as valid and 44/82 total genus-groups, based on over 1,800 ultraconserved elements (UCE). We also use the UCE tree to enrich a mitochondrial COI tree with even greater taxon sampling. Our results agree with most past studies in the reciprocal monophyly of Michener’s Lasioglossum and Hemihalictus series, Dialictus and Hemihalictus sensu Gibbs, the inclusion of Homalictus within Lasioglossum, Rostrohalictus as a monotypic subgenus, and the sister relationship of Lasioglossum with Mexalictus+Patellapis+Thrincohalictus+Halictus. We recognize 25 valid subgenera in Lasioglossum, establish 6 new synonymies, and expand the limits of the subgenus Eickwortia to include 18 species formerly placed in Dialictus. Diagnostic characters and figures are given for the newly-defined Eickwortia.