CONICET | Buscador de Institutos y Recursos Humanos

Premise of the study In the North American Arctic the existence of one or several taxa closely related to Deschampsia cespitosa var. cespitosa has remained a puzzle for many years. Extreme morphological variation, lack of clear limits between the alleged forms, and an extended geographic range often rendering identification keys incomplete raised the question of it is one or several species.Methods In order to clarify this, we carried out a morphological and molecular study of D. cespitosa var. cespitosa and related taxa on 201 herbarium specimens of northern North America (Alaska, Canada and Greenland) using multivariate statistics, ITS and the cpDNA marker trnK-rps16. Fifty-three morphological characters were recorded from all specimens, while sequences were retrieved from 167 specimens.Key Results Results show that Deschampsia cespitosa (L.) P. Beauv. var. cespitosa, D. cespitosa subsp. alpina (L.) Tzvelev, D. cespitosa subsp. beringensis (Hultén) W. E. Lawr., D. brevifolia R. Br., D. cespitosa (L.) P. Beauv. subsp. glauca (Hartm.) C. Hartm., D. mackenzieana Raup, D. cespitosa subsp. orientalis Hultén, and D. pumila (Griseb.) Ostenf. differed significantly in few morphological variables, but molecularly are a closely related group with several sequences and haplotypes that are nearly identical.Conclusions On the whole the evidence points to the existence of a single species, Deschampsia cespitosa. The occurrence of slighty different morphological types related to specific geographical distributions allows the recognition of three additional taxa at the infraspecific level corresponding to D. cespitosa subsp. alpina, D. cespitosa subsp. beringensis and D. brevifolia. All studied taxa showed morphological variation in a gradient, suggesting the existence of phenotypic plasticity.