Molecular phylogenies of Udoteaceae (Bryopsidales, Chlorophyta) reveal nonmonophyly for Udotea, Penicillus and Chlorodesmis

Generic delineation within and among the udoteacean genera Udotea, Penicillus, Rhipocephalus and Chlorodesmis has remained provisional because of conflicting evidence from different sets of traits, especially between reproductive structures and vegetative morphology. The ribosomal DNA phylogeny presented here contradicts the classical generic concepts within the Udoteaceae by revealing traditional genera to be polyphyletic. Based on this study, it was reported that the brush of Penicillus is essentially an uncorticated Udotea blade in which siphons have lost adherence. In fact, this Penicillus morphology arises twice independently. Similarly, the simple uniaxial thallus of Chlorodesmis has evolved through secondary reduction or neoteny. Siphon anatomy of vegetative thalli does not delineate natural groups perfectly. However, the shape of reproductive structures and the size of macrogametes appear to circumscribe natural taxa well. Overall sequence divergence within Udotea and its allied species in Chlorodesmis, Penicillus and Rhipocephalus is low and indicates relatively young and rapidly diversifying lineages.