Tribe Rhynchosporeae (ca. 386 spp.; Cyperaceae) has high levels of endemicity (≥44%) in tropical/subtropical American savannas and can provide insights into the diversification of their biotas. Wind pollination, occupation of savanna habitat, and a C3 photosynthetic pathway are common in the tribe, but showy (presumably insect-pollinated) inflorescences, occupation of forest habitat, and a C4 pathway also occur. We reconstructed a dated phylogenetic hypothesis for 79 taxa, inferring a mean crown-group age of 56 million years. Fitch parsimony infers the most recent common ancestor to have occupied a savanna habitat with 8 or more shifts to forest. Features associated with insect pollination—white bracts and spikelets—were shown to evolve 6 or more times, but were not correlated with the shifts to forest habitat. We found evolutionary correlations in the pairwise comparisons of bract color versus spikelet color, and bract positioning versus bract color. Members with C4 anatomies, though anatomically variable, form a clade with a crown age of 19 million years.
↧