Phylogeny and new generic-level classification, and historical biogeography of the Eucera complex (Hymenoptera: Apidae)

Authors: ACHIK, DORCHIN - Cornell University; LOPEZ-URIBE, MARGARITA - Cornell University; Griswold, Terry; PRAZ, CHRISTOPHE - University Of Neuchatel; DANFORTH, BRYAN - Cornell University

Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2017
Publication Date: 11/6/2017
Citation: Achik, D., Lopez-Uribe, M.M., Griswold, T.L., Praz, C.J., Danforth, B.N. 2017. Phylogeny and new generic-level classification, and historical biogeography of the Eucera complex (Hymenoptera: Apidae). Molecular Phylogenetics and Evolution. 119:81-92.

Interpretive Summary: Longhorn bees (Eucerini) are a diverse group of mostly large bees (bigger than a honey bee) that includes important pollinators of both wild and agricultural plants. The name comes from the very long antenna found on males of many of the species. Longhorn bees are found across much of world. They are solitary bees with each female making her own nest in the ground. While we know a fair amount about the biology of Eucerini, the evolutionary relationships among the tribe remain unclear, particularly in one large group of about 390 species called the “Eucera complex”. In this paper we explore the relationships in this group using DNA sequences and body structures. The result is a much simpler generic classification with the majority of the species in one genus, Eucera. Results also strongly suggest a new genus should be described for one small group of bees, the “venusta-group”. Body structures that can be used to recognize genera and subgenera are identified. The result of this study is a more stable classification on which to base studies of plant preferences for this group of pollinators.

Technical Abstract: The longhorn bee tribe Eucerini (Hymenoptera: Apidae) is a diverse, widely distributed group of solitary bees that includes important pollinators of both wild and agricultural plants. While there is considerable knowledge on the biology of Eucerini, evolutionary relationships within this complex tribe remain unclear. About half of the species in the tribe, currently assigned to the genus Eucera and to a few other related genera, comprise a large species complex (ca. 390 species), in which generic boundaries are arbitrary due to morphological intergradation among taxa. Using ca. 6,700 nucleotide bases from six gene fragments, 142 morphological characters, and more than 100 taxa, we present the first comprehensive molecular, morphological, and combined phylogenetic analyses of the relationships within the ‘Eucera complex’. We propose an alternative classification that is congruent with our phylogeny, and provides a practical framework in terms of taxon diagnosis. Because we favor a classification that maximizes generic stability and ease of identification, we synonymize most generic names under an expanded genus Eucera. Thus, Tetralonia, Xenoglossa, and Syntrichalonia are reduced to subgenera, and Synhalonia is retained as a subgenus of Eucera. Xenoglossodes is reestablished as a valid subgenus of Eucera to include the Nearctic members of the current genus Tetraloniella. Other genera that are invalidated under the proposed classification include Tetraloniella, Cubitalia, Peponapis, and Cemolobus. Finally, the venusta-group, currently placed in the Eucera, subgenus Synhalonia, appears as an isolated lineage in our molecular analyses, sister to all Eucera lineages and to the monotypic genus Simanthedon. We therefore suggest generic status for this group. Based on analysis of morphological traits evolution, we identify important synapomorphies for lineages in this complex, question some functional traits used traditionally as diagnostic characters, and discuss the need to evaluate convergent loss or gain of functional traits to avoid the use of potentially homoplasious characters in classifications.