Phylogenomics and historical biogeography of the cleptoparasitic bee genus Nomada (Hymenoptera: Apidae) using ultraconserved elements

Authors: ODANAKA, KATHERINE - York University; Branstetter, Michael; Tobin, Kerrigan; REHAN, SANDRA - York University

Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2022
Publication Date: 3/24/2022
Citation: Odanaka, K.A., Branstetter, M.G., Tobin, K.B., Rehan, S.M. 2022. Phylogenomics and historical biogeography of the cleptoparasitic bee genus Nomada (Hymenoptera: Apidae) using ultraconserved elements. Molecular Phylogenetics and Evolution. 170. Article 107453. https://doi.org/10.1016/j.ympev.2022.107453.
DOI: https://doi.org/10.1016/j.ympev.2022.107453

Interpretive Summary: Phylogenomics and historical biogeography of the cleptoparasitic bee genus Nomada (Hymenoptera: Apidae) using ultraconserved elements: The bee genus Nomada includes over 800 species globally, including 265 species in the U.S.A., and represents the largest group of brood parasitic bees known. The genus is commonly collected in bee surveys and is of value as a proxy for overall bee diversity because of its reliance on other bees for reproduction. To date, the phylogeny of the genus has only been studied using morphological characters and no effort has been made to infer the group’s biogeographic history. Using ultraconserved element (UCE) molecular sequence data and extensive taxon sampling the phylogeny of the genus and its biogeographic history were examined. The resulting phylogeny revealed that several morphologically defined species groups within the genus are not valid and that the genus likely originated in the northern hemisphere during the late Cretaceous, a scenario that contradicts previous hypotheses. The biogeographic scenario also identified repeated dispersal across land bridges within the northern hemisphere. This work greatly improves understanding of the diversity and evolution of Nomada bees and is foundational for future work to improve the group’s taxonomy and classification.

Technical Abstract: The genus Nomada Scopoli (Hymenoptera: Apidae) is the largest genus of brood parasitic bees with nearly 800 species found across the globe and in nearly all biogeographic realms except Oceania and Antarctica. There is no previous molecular phylogeny focused on Nomada despite their high species abundance nor is there an existing comprehensive biogeography. Using ultraconserved element (UCE) phylogenomic data, we constructed the first molecular phylogeny for the genus Nomada and tested the monophyly of 16 morphologically established species groups. We also estimated divergence dates using fossil calibration points and inferred the origin and diversification of this genus around the globe. Our phylogeny provided support for 14 of the 16 previously established species groups, with two groups needing to be unified into a single group and another found to be paraphyletic. All remaining species groups were found to be monophyletic. Historical biogeographic reconstruction indicates that Nomada originated in the Holarctic ~65 Mya. Geodispersal into the southern hemisphere occurred three times; once during the Eocene into the Afrotropics, once during the Oligocene into the Neotropics, and once during the Miocene into Australasia. Geodispersal across the Holarctic was most frequent and occurred repeatedly throughout the Cenozoic era, using the De Geer, Thulean, and the Bering Land Bridges. This is the first instance of a bee using both the Thulean and De Geer land bridges and has implications of how early bee species dispersed throughout the Palearctic in the late Cretaceous and early Paleogene.