Bee Genesis Revisited: Increased Taxon Sampling Reveals Non-monophyly and Asymmetrical Diversification in Apoidea
The fluctuating realtionship of bees to Sphecidae sensu lato (s.l.) (=apoid) wasps has long led to changes in higher-level classification and hypotheses of the bee sister group. Today, they share the superfamily Apoidea, which includes 20 families, and the bee sister group is considered to be the former subtribe Ammoplanina (=Ammoplanidae). However, there has been minimal sampling of Ammoplanidae and its former subfamily Pemphredoninae across studies. Here, our aims were to (1) test interfamilial relationships and sister group hypotheses with different data types and increased taxon sampling, and (2) elucidate the timing of key radiations across Apoidea with novel fossil evidence. We compiled an ultraconserved element (UCE) dataset, both de novo and mined from published whole genomes and transcriptomes. We sequenced all but five of the 42 genera of former Pemphredoninae and 9 of the 11 genera of Ammoplanidae. Divergence time estimation was done with 11 fossils, 7 of which had never been used to calibrate a phylogeny before. Our results corroborate that a clade of Ammoplanidae is the sister group to bees yet reveal that the family is not monophyletic. We identified three distinct Ammoplanidae clades: (1) Pulverro and Ammoplanops (=Ammoplanopsidae, fam. nov.); (2) Ammostigmus sp. nov.; and (3) the sister group to bees, Ammoplanidae sensu stricto (s.s.). Our findings accentuate the asymmetrical diversification between bees and their sister group, which now includes only 120 extant species, and how different data types and increased taxon sampling may split clades, leading to further changes in classification and age estimates.