Data from: Large-scale patterns of diversification in the widespread legume genus Senna and the evolutionary role of extrafloral nectaries

Unraveling the diversification history of old, species-rich and widespread
clades is difficult because of extinction, undersampling and taxonomic
uncertainty. In the context of these challenges, we investigated the
timing and mode of lineage diversification in Senna (Leguminosae) to gain
insights into the evolutionary role of extrafloral nectaries (EFNs). EFNs
secrete nectar, attracting ants and forming ecologically important
ant-plant mutualisms. In Senna, EFNs characterize one large clade
("EFN clade"), including 80% of its 350 species. Taxonomic
accounts make Senna the largest caesalpinioid genus, but quantitative
comparisons to other taxa require inferences about rates. Molecular dating
analyses suggest that Senna originated in the early Eocene, and its major
lineages appeared during early/mid Eocene to early Oligocene. EFNs evolved
in the late Eocene, after the main radiation of ants. The EFN clade
diversified faster, becoming significantly more species-rich than non-EFN
clades. The shift in diversification rates associated with EFN evolution
supports the hypothesis that EFNs represent a (relatively old) key
innovation in Senna. EFNs may have promoted the colonization of new
habitats appearing with the early uplift of the Andes. This would explain
the distinctive geographic concentration of the EFN clade in South
America.