A new genus of eucerine bees endemic to southwestern North America revealed in phylogenetic analyses of the Eucera complex (Hymenoptera: Apidae: Eucerini)

The Eucera complex (Apidae: Eucerini), which traditionally included the genus Eucera and a few other related genera comprises a large complex in which generic boundaries have long remained unsettled. Based on comprehensive phylogenetic analyses, a recent study completely reorganized the generic classification of the group. Unexpectedly, both morphological and molecular analyses indicated that the taxon known as the venusta-group of the Eucera subgenus Synhalonia is in fact an isolated early diverging lineage, distantly related to Synhalonia. The only three species currently known in the venusta-group are endemic to arid and semi-arid habitats of the southwestern USA and Baja California in Mexico, and are relatively rare in entomological collections. Here we recognize a new genus: Protohalonia Dorchin gen.n., compare its morphology with related genera, and present a revision and identification keys for the three species included. We reexamine the phylogenetic position of the new genus based on our previously published molecular and morphological datasets, which we supplement with data for the remaining Protohalonia species. All analyses recovered Protohalonia as a monophyletic group with strong support, sister to Simanthedon in the molecular and combined dataset analyses, or Simanthedon plus Martinapis in the morphological analysis; these taxa combined were sister to all the remaining lineages of the Eucera complex which together form the genus Eucera. Based on ancestral state reconstruction we identify unique traits supporting the monophyly of Protohalonia and document important diagnostic traits. Our results show that this taxon possesses a combination of apomorphic and plesiomorphic character states that appear in parallel in either the Eucera complex or outgroup taxa consistent with the phylogenetic position of the new genus. Lastly, we also propose replacement names for six new homonymies resulting from our recent classification of the Eucera complex.