The relationships of Lycopodium and Lycopodiella (Lycopodiaceae) were investigated based on two plastid data sets (rbcL gene and trnL intron) from a representative sample of 21 species. Separate and combined analyses of the data reveal consistent patterns of relationship. There is strong support for monophyly of Lycopodium and Lycopodiella. There is also support for monophyly of species groups or sections sensu Øllgaard (Lycopodium, Diphasium, Magellanica, Complanata, Lycopodiella, and Campylostachys). The combined data provide new evidence of relationships between subgeneric groups. In Lycopodium, section Pseudodiphasium groups with section Magellanica, section Obscura groups with section Diphasium, and section Annotina groups with section Lycopodium. In Lycopodiella, sections Lateristachys and Caroliniana group with section Campylostachys and this group is sister to section Lycopodiella. Tentative calibration of the phylogenetic tree using fossil evidence indicates a minimum age of Early Jurassic (208 Myr) for the split between Lycopodium and Lycopodiella. Reticulate fossil spores from Upper Permian records are potentially of Lycopodium affinity and indicate that early cladogenesis in Lycopodium may be even older. An evaluation of biogeographic and phylogenetic patterns in these two genera shows a striking difference from that in Huperzia. Sections within Lycopodium and Lycopodiella have broad geographic distributions, whereas molecular data partition the much larger Huperzia group into predominantly neotropical and paleotropical clades.

Communicating Editor: Alan Whittemore