Systematics Section / ASPT
Waterway, Marcia .
Dismantling Carex section Hymenochlaenae : biogeographic implications.
INTERPRETING biogeographic patterns requires a good understanding of the evolutionary history of a lineage. Carex section Hymenochlaenae, as circumscribed by Kukenthal in his 1909 world monograph of the genus, includes species from tropical to arctic regions on five continents with no clear geographic pattern. Phylogenetic analyses based on sequence data from five non-coding DNA regions (2 nuclear, 3 chloroplast) reveal that section Hymenochlaenae is polyphyletic. Most species studied to date fall into 5 distinct clades, each with different geographic affinities. The largest clade (“expanded Porocystis” with >25 spp.) is strictly North American and includes species from two other sections. Based on the low levels of sequence divergence within this clade, it appears to be a recent radiation with distinct eastern and western lineages. Two North American species—C. obispoensis, endemic to southern California, and C. cherokeensis, endemic to the southeastern U.S. and lectotype for section Hymenochlaenae—form a second clade with species from Europe, Asia, and Australia. Another European species, C. sylvatica, groups with other European species in section Rhynchocystis. Carex prasina, a species of wet, shaded habitats in North America, is part of a clade with circumboreal peatland species of sections Limosae and Racemosae. Two other North American species, C. sprengelii and C. assiniboinensis are of uncertain affinities, occurring on different early-diverging branches within the large subgenus Carex/Vigneastra clade. Two species of eastern Asian forests form a fifth group that is most divergent from the others. These multispicate species group together with Uncinia, Kobresia, Cymophylllus, and unispicate Carex species in the “reduced clade” of tribe Cariceae, rather than in the subgenus Carex/Vigneastra clade.
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1 - McGill University, Department of Plant Science, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec, H9X 3V9, Canada
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 1:45 PM