A re-evaluation of species limits in Canadian Arctic Island Puccinellia (Poaceae):: resolving key characters

This study examined morphological variation for species of Puccinellia that have traditionally posed problems of identification in the Canadian Arctic Archipelago. The first part of the study involved a re-examination of several characters that were difficult to define or describe. Microscopic examination of lemma and glume apices revealed that the characters "erose-ciliolate" lemma and glume apex margins are more accurately divided into two characters: degree to which they are erose, and presence of trichomes. These trichomes consist of acute or acuminate cells that protrude 15-35 mum from the margin, sometimes with a spinulose tip up to 10 mum long. The term "thickened pedicel" is clarified to mean thickened below the apex in relation to the apex. The second part of the study involved preliminary morphometric analyses on the above-mentioned revised characters, plus other characters previously shown to have low plasticity in this genus, for 10 recognized species that are difficult to distinguish. Many species or species complexes resolved to a small degree, but no taxa formed distinct groups. Correlations among many characters were low, accounting for a low percentage of variation explained by the first few principal components. Hypotheses of species boundaries and a preliminary revised key to species and species groups, incorporating findings from this study, are presented.