Relationship between phenotypic differentiation and glacial history in a widespread Alpine grassland herb

In the European Alps, alpine species were able to survive periods of glaciation by retreating to lower-lying refugia surrounding the Alps. This temporary separation of populations in refugia has often led to genetic differentiation and the appearance of phylogeographic lineages, which are still detectable after postglacial recolonisation. Recently, evidence has been accumulating that glacial history also affected differentiation of phenotypic traits, but it is yet unknown to what extent postglacial connectivity among populations influenced the signature left behind by the history of glaciation. In this study, we demonstrate differentiation in phenotypic traits among three phylogeographic lineages of the widespread subalpine grassland herb, Geum montanum, using a common garden approach. We observed regional differentiation in 5 out of 16 traits, which was a small portion compared with a closely related species that has been previously studied, Geum reptans. This may possibly be due to species-specific differences in their respective distributions: G. montanum has well-connected populations whereas G. reptans occurs more often in isolated high-alpine environments. Results of a clipping treatment, designed to address responses in phenotypic traits to stress, showed regional differentiation in the response in number of flowers produced. This is potentially due to adaptations shaped by unknown histories of herbivory during glacial survival. We suggest that glacial history may leave its mark on the current phenotypic variability even of Alpine plants that are relatively common with well-connected populations