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Abstract We reconstruct the phylogeny of the most speciose genus of cuckoo bees, genus Nomada Scopoli, 1770, using 221 species from throughout its distribution, yet with a strong emphasis on the West Palearctic. For phylogenetic reconstruction, we sequenced ultraconserved elements, allowing robust phylogenetic estimates with both concatenation and coalescent-based methods. By integrating extensive information on Nomada host records, we study macroevolutionary patterns of host associations, transitions, and phylogenetic conservatism. Using Bayesian divergence time estimates, we assess the historical biogeography of the genus, focusing on the West Palearctic. Our results show that Nomada likely originated in the Eastern Mediterranean and Near Eastern region, and likely expanded its range to a near-global distribution from there. We recovered long-standing phylogenetic conservatism in the host usage of Nomada and provided strong statistical evidence for an ancestral host association with Andrena and its most recent common ancestor. However, host transitions occurred multiple times independently in the natural history of Nomada, and species of the genus are brood parasites in at least 5 genera and 4 different families of bees in the Old World. At last, we systematically revise the taxonomy of the Old World Nomada by integrating morphological study with our well-supported phylogenetic estimates. We re-establish the genus Acanthonomada Schwarz, 1966, stat. res., as a distinct, second genus in the tribe Nomadini. We recognize 13 subgenera for Nomada, 9 of which are described as new: Afronomada Straka and Bossert, subgen. nov., Colliculla Straka, subgen. nov., Gestamen Straka, subgen. nov., Hungias Straka, subgen. nov., Mininomada Straka, subgen. nov., Nomacolla Straka, subgen. nov., Nomonosa Straka, subgen. nov., Plumada Straka, subgen. nov., and Profuga Straka, subgen. nov. Aside from the subgenus Nomada s.s., we reinstitute 3 previously synonymized subgenera: Heminomada Cockerell, 1902, stat. res., Holonomada Robertson, 1903, stat. res., and Hypochrotaenia Holmberg, 1886 stat. res. A total of 15 subgeneric names are formally synonymized with the newly established subgeneric concepts. 

Abstract Despite recent advances in phylogenomics, the early evolution of the largest bee family, Apidae, remains uncertain, hindering efforts to understand the history of Apidae and establish a robust comparative framework. Confirming the position of Anthophorinae—a diverse, globally distributed lineage of apid bees—has been particularly problematic, with the subfamily recovered in various conflicting positions, including as sister to all other Apidae or to the cleptoparasitic Nomadinae. We aimed to resolve relationships in Apidae and Anthophorinae by combining dense taxon sampling, with rigorous phylogenomic analysis of a dataset consisting of ultraconserved elements (UCEs) acquired from multiple sources, including low-coverage genomes. Across a diverse set of analyses, including both concatenation and species tree approaches, and numerous permutations designed to account for systematic biases, Anthophorinae was consistently recovered as the sister group to all remaining Apidae, with Nomadinae sister to (Apinae, [Xylocopinae, Eucerinae]). However, several alternative support metrics (concordance factors, quartet sampling, and gene genealogy interrogation) indicate that this result should be treated with caution. Within Anthophorinae, all genera were recovered as monophyletic, following synonymization of Varthemapistra with Habrophorula. Our results demonstrate the value of dense taxon sampling in bee phylogenomics research and how implementing diverse analytical strategies is important for fully evaluating results at difficult nodes.