Phylogeny of Lycopodiaceae (Lycopsida) and the Relationships of Phylloglossum drummondii Kunze Based on rbcL Sequences

A cladistic analysis based on rbcL sequences from a representative sample of 12 species yields a single most parsimonious tree that supports monophyly of Lycopodiaceae, Lycopodium, and Lycopodiella. Huperzia is resolved as paraphyletic to the morphologically divergent, monotypic Australasian Phylloglossum. The Huperzia-Phylloglossum clade is strongly supported and is sister group to a Lycopodium-Lycopodiella clade. These results provide the first clear evidence for the relationships of the problematic Phylloglossum drummondii. Profound differences in life cycle and morphology between Phylloglossum and other Lycopodiaceae are interpreted in terms of pedomorphosis (specifically, progenesis) and are viewed as adaptive responses to drought and brush fire. Our results show that rbcL sequence divergence among neotropical species of the supposedly ancient genus Huperzia is extremely low and that additional data will be necessary to resolve relationships among epiphytes and ground-living species. These surprisingly low levels of sequence divergence indicate that most living species diversity within Lycopodiaceae is of relatively recent origin Our results are consistent with a late Cretaceous or early Tertiary origin and diversification of epiphytic species within Huperzia, and these events may be linked to the diversification of angiosperms.