Systematics Section / ASPT
Naczi, Robert F. C. , Ford, Bruce A. , Bryson, Charles T. .
Revision of Carex digitalis (Cyperaceae), a Common Sedge of Eastern North America.
CAREX digitalis is a common, widespread sedge of mesic deciduous forests of eastern North America. Recent treatments of C. digitalis recognize three varieties for the species: var. digitalis, var. floridana, and var. macropoda. However, field and herbarium studies have led us to suspect that this taxonomy may be too conservative. Accordingly, the purpose of this investigation is to determine the number of taxa in the C. digitalis complex, identify the best diagnostic characters for them, and determine the appropriate rank for each of the taxa. To address these questions, we studied macromorphology, amplified fragment length polymorphisms (AFLPs), geography, and ecology of the C. digitalis complex in the field, herbarium, and laboratory. Univariate and multivariate statistical analyses of morphologic data identify three taxa in C. digitalis. Carex digitalis var. macropoda is the most distinctive member of the group, unique in its relatively narrow leaf blades, long peduncles of the terminal spikes, and long staminate scales. Relatively long lateral spikes and relatively long bract blades diagnose C. digitalis var. digitalis. Lateral spikes with closely overlapping, relatively long perigynia characterize C. digitalis var. floridana. Analyses of AFLPs also distinguish three taxa in C. digitalis, corresponding to the same groups identified by morphologic analyses. Each taxon has a unique geographic range, with var. digitalis extending farther north than the others (to southern Canada). Carex digitalis var. macropoda occurs throughout the southeastern U.S.A., whereas var. floridana occurs mostly on the Coastal Plain in the southeastern U.S.A. Syntopy provides further evidence of the distinctness of these taxa since they maintain their morphologic and genetic identities when they co-occur, with no hybrids or intermediates detected. Data from these various sources indicate each of the three varieties in the C. digitalis complex should be treated as a species.
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1 - Delaware State University, Claude E. Phillips Herbarium, Department Agriculture & Natural Resources, 1200 N Dupont Highway, Dover, Delaware, 19901-2277, USA
2 - University of Manitoba, Department of Botany, Winnipeg, Manitoba, R3T 2N2, Canada
3 - U.S. Dept. Agriculture-Ag. Research Service (USDA-ARS), Southern Weed Science Research Unit, P.O. Box 350, 141 Experiment Station Road, Stoneville, Mississippi, 38776, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 1:00 PM