What can morphology and isozymes tell us about the history of theDryas integrifolia–octopetalacomplex?

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Abstract
An earlier study of the morphological variation in the circumpolar genusDryasin Greenland revealed that populations in east Greenland are highly variable and this variation was interpreted as a hybrid zone betweenD. octopetalaandD. integrifolia.It was proposed that populations ofDryasin east Greenland immigrated postglacially from Svalbard. The purpose of our study was to investigate the population structure of theDryas integrifolia–octopetalacomplex using a combination of morphological and genetic characters. Populations ofDryaswere sampled in Greenland, Svalbard, Iceland and north Scandinavia (Sweden). The morphological traits clearly separated west Greenland from Svalbard, Iceland and north Scandinavia. A large number of individuals from east Greenland and some from north Greenland could be interpreted as hybrids between the morphs. The genetic pattern was, however, partly different as the greatest amount of differentiation among regions was found between west and north Greenland (FRT = 0.65). The highest degree of genetic variation appeared within east Greenland. This was in accordance with the putative hybrid origin of the populations, as concluded based on the morphological results. The total amount of genetic differentiation found among the six regions (FRT = 0.61) was larger than between the two species (FRT = 0.44). The genetic pattern matched the proposed postglacial migration routes.