A systematic revision of the genus Diastatea (Campanulaceae)

Diastatea (Campanulaceae-Lobelioideae) is a genus of small, herbaceous annuals found mostly in Mexico. Differences in the number of recognized species in the historical treatments, and the lack of a phylogeny, suggest that a revision of the genus is necessary. Species boundaries and species level relationships were tested based on a sampling of nearly 50 individuals. Sequences of the chloroplast spacer regions, atpB-rbcL and ndhF-rpl32, as well as the nrITS were generated and then analyzed using maximum likelihood, parsimony, and Bayesian inference methods. Analyses of the combined chloroplast dataset and the ITS dataset both produced congruent topologies. Two strongly supported clades of Diastatea were found in all analyses and can be distinguished morphologically by leaf shape and pubescence, hypanthium shape, and the presence or absence of a gibbous projection on the ventral side of the corolla. A morphological treatment of the genus revealed one new species, one new subspecies (Diastatea tenera subsp. durangensis), and elevated an existing subspecies to specific rank (Diastatea ciliata).