Systematics of the Halimolobine Brassicaceae: Evidence from Three Loci and Morphology

Abstract Relationships among Halimolobos, Mancoa, Pennellia, and Sphaerocardamum have been controversial. Higher level studies, using cpDNA data from the chloroplast encoded ndhF and trnL intron, suggested that some species of these genera represent a monophyletic group: the halimolobine clade. The research presented here focuses on the halimolobine clade with denser intra and inter-specific sampling. The primary aims of the project were: (1) to further test the monophyly of the halimolobine clade; (2) to test the monophyly Halimolobos, Mancoa, Pennellia, and Sphaerocardamum; and (3) to study the evolution of morphological characters in the clade. Data were generated from the trnL-F region, nrDNA ITS, pistillata intron one, and 17 non-molecular characters. The difficulties associated with incorporating these data into simultaneous analyses are discussed and a strategy is presented. Separate and simultaneous analysis confirmed a monophyletic core group of halimolobine species. The strict consensus tree contained five well-supported halimolobine subclades: Sphaerocardamum, Pennellia plus Arabis tricornuta, Mancoa bracteata plus M. foliosa, a narrowly defined Halimolobos, and a clade consisting of a subset of Halimolobos and Mancoa species. Individual morphological characters vary in their utility for classification of the group. However, the majority of the characters provide some grouping information within the halimolobine clade. Communicating Editor: Paul Wilson