Phylogenetic utility of the major opsin in bees (Hymenoptera: Apoidea): a reassessment.

Major opsin (LW Rh) DNA sequence has been reported to provide useful data for resolving phylogenetic relationships among tribes of corbiculate bees based on analyses of 502 bp of coding sequence. However, the corbiculate tribes are believed to be of Cretaceous age, and strong support for insect clades of this age from small data sets of nucleotide sequence data has rarely been demonstrated. To more critically assess opsin's phylogenetic utility we generated an expanded LW Rh data set by sequencing the same gene fragment from 52 additional bee species from 24 tribes and all six extant bee families. Analyses of this data set failed to provide substantial support for monophyly of corbiculate bees, for relationships among corbiculate tribes, or for most other well-established higher-level relationships among long-tongued bees. However, monophyly of nearly all genera and tribes is strongly supported, indicating that LW Rh provides useful phylogenetic signal at lower taxonomic levels. When our expanded LW Rh data set is combined with a morphological and behavioral data set for corbiculate bees, the results unambiguously support the traditional phylogeny of the corbiculate bee tribes: (Euglossini + (Bombini + (Meliponini + Apini))). This implies a single origin of advanced eusocial behavior among bees rather than dual origins, as proposed by several recent studies.