HAUFLER, CHRISTOPHER H.1*, ALAN R. SMITH2, HARALD SCHNEIDER2, TERRI HILDEBRAND1, RAY CRANFILL2, and TOM A. RANKER3. 1Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045; 2University Herbarium, University of California, Berkeley, CA 94720; 3University Museum and Department of EPO Biology, University of Colorado, Boulder, CO 80309. - Polypodium redefined: Morphology, biogeography, and DNA sequences provide clues to lineages.
The ±180 species usually assigned to Polypodium appear to
represent a polyphyletic assemblage of nearly exclusively New World
species. Rooted to Old World genera, most Polypodium species
occur in the continental upland tropics, with relatively little
diversification on islands, and only the monophyletic P.
vulgare complex found in temperate zones. Scale characters appear
particularly significant for circumscribing apparently natural groups
in this large genus. Glabrous and scaly-leaved species constitute
separate lineages, with bicolorous, concolorous, and clathrate rhizome
scales useful for further subdivisions. Other significant
morphological features include complexity of vein anastamoses, numbers
of soral rows, and patterns of rhizome branching. Separate and
combined analyses of sequences from rbcL, rps4, and
trnL-F yield insights for testing hypothesized subdivisions of
Polypodium and determining interrelationships between
Polypodium and other genera in the Polypodiaceae.
Polypodium should be strictly applied to the glabrous-leaved
species, whereas Pleopeltis appears to be the generic name that
will be used for the scaly-leaved species. Some regularly included
Polypodium species (e.g., P. triseriale and P.
ptilorhizon) appear to have a tenuous connection to other members
of the genus. Pecluma emerges consistently as an outgroup to
the scaly polypods and not closely allied to the grammitids. Other
close relatives may include Campyloneurum and Niphidium,
although the precise position of these segregate genera has been
difficult to determine. These analyses help provide targets for future
biosystematic studies of tropical American genera and will aid in
defining general patterns and processes of diversification among
Key words: ferns, Polypodiaceae, Polypodium, pteridophytes, systematics