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Abstract The genusTauschiahas long been a source of taxonomic consternation for researchers. The group of species currently included in this genus are distributed primarily across the western United States and Mexico, but a few species occur in Central America and northern South America. Its circumscription is highly problematic, and its species have been moved countless times between more than a dozen genera. The advent of molecular phylogenetics has allowed some testing of generic boundaries inTauschiaand related taxa, but the sampling of previous studies was limited to a few species representing too small of a range to sort out the confusion. Here, we expand the sample size to include plants from throughout the range of the genus and use this to examine relationships among species ofTauschia, as well as to the larger clades to which it belongs within tribe Selineae. We also detail the complex taxonomic history ofTauschiaand related genera, provide a complete synonymy of the genus as it is currently defined, and confirm the polyphyly ofTauschiavia phylogenetic analysis of nuclear and cpDNA sequences. 

Abstract Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods^1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome^3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins^5–7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes⁸. This 15-fold increase in genus-level sampling relative to comparable nuclear studies⁹provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade.