Phylogeny, diversification patterns and historical biogeography of euglossine orchid bees (Hymenoptera: Apidae)

Abstract

The orchid bees constitute a clade of prominent insect pollinators distributed throughout the Neotropical region. Males of all species collect fragrances from natural sources, including flowers, decaying vegetation and fungi, and store them in specialized leg pockets to later expose during courtship display. In addition, orchid bees provide pollination services to a diverse array of Neotropical angiosperms when foraging for food and nesting materials. However, despite their ecological importance, little is known about the evolutionary history of orchid bees. Here, we present a comprehensive molecular phylogenetic analysis based on ∼4.0 kb of DNA from four loci [cytochrome oxidase (CO1), elongation factor 1-α (EF1-α), arginine kinase (ArgK) and RNA polymerase II (Pol-II)] across the entire tribe Euglossini, including all five genera, eight subgenera and 126 of the approximately 200 known species. We investigated lineage diversification using fossil-calibrated molecular clocks and the evolution of morphological traits using disparity-through-time plots. In addition, we inferred past biogeographical events by implementing model-based likelihood methods. Our dataset supports a new view on generic relationships and indicates that the cleptoparasitic genus Exaerete is sister to the remaining orchid bee genera. Our divergence time estimates indicate that extant orchid bee lineages shared a most recent common ancestor at 27-42 Mya. In addition, our analysis of morphology shows that tongue length and body size experienced rapid disparity bursts that coincide with the origin of diverse genera (Euglossa and Eufriesea). Finally, our analysis of historical biogeography indicates that early diversification episodes shared a history on both sides of Mesoamerica, where orchid bees dispersed across the Caribbean, and through a Panamanian connection, thus reinforcing the hypothesis that recent geological events (e.g. the formation of the isthmus of Panama) contributed to the diversification of the rich Neotropical biota. © 2010 The Linnean Society of London.