Comparative Genital Morphology, Phylogeny, and Classification of the Orchid Bee Genus Euglossa Latreille (Hymenoptera: Apidae), with Distributional Modeling of Adventive Euglossines

Abstract

Orchid bees (tribe Euglossini) are conspicuous members of the corbiculate bees owing to their metallic coloration, long labiomaxillary complex, and the fragrance-collecting behavior of the males, more prominently (but not restricted) from orchid flowers (hence the name of the group). They are the only corbiculate tribe that is exclusively Neotropical and without eusocial members. Of the five genera in the tribe, Euglossa Latreille is the most diverse with around 120 species. Taxonomic work on this genus has been linked historically to the noteworthy secondary sexual characters of the males, which combined with the other notable external features, served as a basis for the subgeneric classification commonly employed. The six subgenera Dasystilbe Dressler, Euglossa sensu stricto, Euglossella Moure, Glossura Cockerell, Glossurella Dressler and Glossuropoda Moure, although functional for the most part, showed some intergradations (especially the last three), and no phylogenetic evaluation of their validity has been produced. A general paucity in the use of male genitalic morphology has also been characteristic for the lineage. Here a comparative study of the male genitalic morphology for Euglossa is presented, and in turn, along with other external morphological features, used as a source of characters included in a phylogenetic analysis. A total of 41 Euglossa species representing the taxonomic diversity within the genus (all subgenera and species groups) plus five taxa as outgroups, and 79 characters are included in a comprehensive cladistic treatment. The resulting 64 shortest trees combined in a strict consensus tree recover as natural groups the subgenera Dasystilbe (monotypic), Euglossa s. str., and Euglossella (sister to all other Euglossa s. lat.). Glossura appears as paraphyletic in a derived clade that also includes Glossuropoda (sensu Moure) and some Glossurella; Glossura is proposed to be expanded to include all the species groups in this derived clade. Most Glossurella form a heterogeneous paraphyletic assemblage, and the subgenus is proposed to be narrowed to include the monophyletic group formed by E. bursigera Dressler and allies. A morphologically distinctive group in the Glossurella grade is also proposed as a new subgenus with E. oleolucens Dressler as type species, while the remaining species in the grade are classified as Euglossa incertae sedis. Recent molecular phylogenetic work largely agrees with the results here presented. The presence of two adventives orchid bee species in the USA is analyzed using occurrence data across their natural ranges to produce Species Distribution Models, so that the recently discovered naturalized populations of Euglossa viridissima Friese in southeastern Florida are projected not to expand beyond the Florida Peninsula, and the isolated records of Eulaema polychroma (Mocsáry) in the southwestern USA are most likely due to individual dispersion events or human introduction.