Les, Donald H. , Murray, Nancy M. , Tippery, Nicholas P. .
Systematics of Potamogeton vaseyi and P. gemmiparus (Potamogetonaceae), two imperiled aquatic plants.
Potamogeton is a taxonomically difficult genus of aquatic monocotyledons, which has received limited phylogenetic study using molecular data. The group is known for extensive vegetative plasticity, confusing patterns of morphological variation and propensity for hybridization. Potamogeton gemmiparus and P. vaseyi are of conservation concern in North America where both are listed as imperiled. These vegetatively similar species are particularly difficult to distinguish in the absence of floating leaves and have been suspected to represent conspecific variants. We studied both species and putatively related taxa to elucidate relationships and to develop an identification method using molecular markers. Phylogenetic analyses of nrITS and trnK 5’ intron sequence data clearly endorse the recognition of P. gemmiparus and P. vaseyi as distinct species but call into question the subspecific circumscription of P. pusillus currently followed in North America. Our data resolved P. pusillus in a clade with P. foliosus, separated substantially from P. berchtoldii (= P. pusillus subsp. tenuissimus), thus supporting the retention of P. berchtoldii as a distinct species. Using molecular cloning techniques, we documented three clear examples of interspecific hybridization (P. foliosus x P. pusillus; P. berchtoldii x P. vaseyi; P. gemmiparus x P. vaseyi). Simple DNA polymorphisms also indicated several P. berchtoldii x P. gemmiparus hybrids. The narrowly distributed P. gemmiparus and P. clystocarpus are similar morphologically and genetically to the wide-ranging P. berchtoldii, with which they both hybridize. Although P. gemmiparus and P. clystocarpus can be recognized as distinct species, it would be more appropriate to treat both as subspecies of P. berchtoldii.
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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - Connecticut Department of Environmental Protection, Bureau of Natural Resources, 79 Elm Street, 6th floor, Hartford, Connecticut, 06106, USA
North American Flora.
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood A/Snowbird Center
Date: Monday, July 27th, 2009
Time: 1:45 PM