Taylor, W. Carl , Hoot, Sara B. .
Phylogeny and Biogeography of Isoetes (Isoetaceae).
ISOETES, an ancient genus of grass-like lycopods, is widely dispersed on islands and on every continent except Antarctica. There are hundreds of species, ranging from ephemeral terrestrials to evergreen aquatics, but a simple, conserved morphology yields few characters and character states to define species and construct a species phylogeny. Widespread distribution and broad habitat diversity among 2x basic diploid species indicate speciation primarily by ecological isolation and genetic divergence. The occurrence of many interspecific hybrids and a polyploid series ranging from 3x to 12x suggest species have also formed through allopolyploidy when divergent species migrated into the same habitats. DNA nucleotide sequences of the nuclear ITS and chloroplast atpB-rbcL spacer region provide many characters to define species and construct a phylogeny. The combined sequence data reveal a clade with possible Gondwanan affinities, a South African clade, a generally Northern Hemisphere clade, a Mediterranean clade, an Asian/Australasian clade, and a New World clade. Some distantly distributed and remotely related species exhibit ecological and morphological convergence. Phylogenetic and biogeographic analyses suggest that vicariance and dispersal have both played a role in the present distribution of Isoetes species.
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1 - National Science Foundation, Division of Environmental Biology, 4201 Wilson Boulevard, Arlington, Virginia, 22230, USA
2 - University of Wisconsin-Milwaukee, Department of Biological Sciences, P.O. Box 413, Milwaukee, Wisconsin, 53201, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 10:30 AM