Alkali grasses (Puccinellia, Poaceae) have traditionally posed problems for identification, and the species in the Canadian arctic archipelago (CAA) are no exception. Although there is considerable morphological variation within the genus, circumscription of taxa is problematical because of overlap of character states and many apparently intermediate specimens. While two species are quite distinct, nine other traditionally recognized species of the CAA have poorly defined species boundaries. The aim of this study was to define the taxonomic limits of species or species groups based on morphological data. In the first part of the investigation, we redefined the character states of several floret and spikelet characters that had been difficult to interpret in previous keys and descriptions. The second part of the study involved analyses on a morphological character set that included these revised characters plus other characters previously shown to have low plasticity in this genus. These analyses showed that P. vahliana was distinct based in part on glume lengths, P. phryganodes was a distinct stoloniferous species, and P. langeana was readily distinguished by its small size and lack of hairs. The remaining species were less clearly distinguished in the ordination analyses performed. The P. arctica aggregate separated from the other taxa, but there was no resolution of species within this group. Hypotheses of species boundaries in the arctic taxa, based on current evidence, are presented. Our present aim is to test these hypotheses with more detailed morphological, anatomical, and molecular analyses. Initial screening of the above taxa for 16 enzymes revealed very low levels of allozyme variation within the genus, with potential markers for P. langeana and P. vahliana in one enzyme system. Restriction site analysis of PCR amplified DNA of eight species showed only minor variation for P. vahliana and P. phryganodes, and none for six other species analyzed.

Key words: Canadian arctic, morphology, ordination analyses, Puccinellia, species boundaries