KORALL, PETRA* AND PAUL KENRICK. Department of Botany, Stockholm University, SE-106 91 Stockholm, SWEDEN, Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom. - Phylogeny of Selaginellaceae based on the plastid gene rbcL: congruence and incongruence with morphology.
Selaginellaceae are a cosmopolitan family of heterosporous lycopods
that originated during the Paleozoic Era. We present a phylogeny of
the group based on rbcL gene sequences from a representative
sample of living species, currently standing at approximately 10% (63
taxa). Monophyly of some widely recognised groups is upheld
(Selaginella, Tetragonostachys, and Articulatae),
but others are shown to be paraphyletic (Stachygynandrum,
Heterostachys, and Ericetorum). We present an evaluation
of some of the morphological data used in previous classifications.
Leaf dimorphism correlates poorly with the major divisions in the
family. However, some of the new groups recognised on molecular
criteria are shown also to have distinctive morphological
characteristics (e.g., patterns of rhizophore development, megaspore
wall ultrastructure). Megaspore wall ultrastructure is singled out as
one characteristic that might be of exceptional utility in calibrating
the phylogenetic tree. Our results have implications for the
interpretation of xerophytic strategies within the family.
"Resurrection plants" appear to have evolved at least three
Key words: lycopods, phylogeny, rbcL, resurrection plants, Selaginellaceae