Waterway, Marcia , Hoshino, Takuji , Masaki, Tomomi , Lapierre, Laura , Lechowicz, Martin , Dabros, Anna , Dragon, Julie A. , Bruhl, Jeremy J. , Wilson, Karen .
Evolution of flooding tolerance in Carex, subgenus Carex.
The species-rich genus Carex with widespread distribution in a variety of habitats in arctic, temperate and subtropical regions is an excellent model system to study the evolution of ecological specialization. A robust estimate of phylogenetic relationships among the >2000 species in Cyperaceae tribe Cariceae is a prerequisite for such studies. Using a phylogenetic hypothesis for Carex subgenus Carex based on sequence data from 5 non-coding DNA regions for 120 species representing the major temperate groups from 4 continents, we demonstrate apparent niche conservatism in flooding tolerance. Although many Carex species occupy moist sites, those species with predominantly wetland distributions (e.g., marsh, shoreline, bog, fen) are restricted to only a few clades, suggesting that flooding tolerance has evolved only a few times. Expanded phylograms, with more complete sampling from each of these wetland clades, support this finding. Sister-species pairs within the wetland clades are often found on different continents and some wetland species occur on multiple continents with little sequence divergence, indicating recent dispersal. Within the wetland clades, closely related species frequently have different pH and water depth tolerances, implying niche differentiation along these ecological gradients as a cause or consequence of speciation. Rhizomatous growth form and diaspores adapted for water dispersal are associated with flooding tolerance in the largest clade of wetland species, but not in all groups of flood-tolerant Carices.
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1 - McGill University, Department of Plant Science, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec, H9X 3V9, Canada
2 - Okayama University of Science, Biosphere-Geosphere System Science, Okayama, Japan
3 - McGill University, Department of Biology, 1205 Avenue Dr. Penfield, Montreal, Québec, H3A 1B1, Canada
4 - University of New England, Botany, Centre For Ecology, Evolution And Systematics, Armidale, New South Wales, 2351, Australia
5 - Royal Botanic Gardens, Mrs Macquaries Road, Sydney, New South Wales, 2000, Australia
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood D/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 2:15 PM