Molecular phylogenetic analyses of Tofieldiaceae (Alismatales): family circumscription and intergeneric relationships.

Tofieldiaceae are a small monocot family comprising about 20 species, mostly distributed in the Northern Hemisphere, with some in northern South America. To clarify the family circumscription, the number of distinguishable genera in the family, and relationships among the genera, we conducted molecular analyses of cpDNA (matK and non-coding trnL-trnL-trnF region) sequences of 17 associated species of Tofieldiaceae, along with 14 species of Acorales, Alismatales, Dioscoreales, Pandanales, and Liliales. Results showed that Tofieldiaceae are monophyletic, comprising all the species assignable to Harperocallis, Isidrogalvia, Pleea, Tofieldia, and Triantha, thus supporting the original family circumscription. Within the family, Pleea is sister to the rest of the family, in which Isidrogalvia is sister to Harperocallis, and Tofieldia to Triantha. Morphological characters supporting the relationships among the genera were briefly discussed.