Morphometric differentiation in Papaver radicatum (Papaveraceae) : Geographic pattern and significance for refugial survival theory

Abstract: The morphometric pattern of variation among and within Scandinavian populations of the alpine species Papaver radicatum was studied. Results from analyses (including multivariate techniques) of capsule and leaf traits of wild-collected and cultivated plants as well as wild-collected seeds show correlated patterns of variation in capsule traits and partly corresponding patterns of variation between capsule and seed traits.On the basis of capsule traits of wild-collected and cultivated plants, two groups are distinguished corresponding to their geographic origin. Such a separation is also, though more weakly, revealed by seed shape. Some of the northernmost populations from southern Norway are grouped together with populations from northern Scandinavia, which can be interpreted in terms of a successive fragmentation of a formely wider range of occurrence. A weak regional pattern of variation is found in the leaf characters of cultivated plants. The results do not support the hypothesis of an equivalent degree of intersubspecies differentiation, nor the idea of in situ refugial survival during the Weichselian glaciation.The pattern of differentiation indicates: (1) an older origin of the bicentric distribution, (2) separation into geographically isolated groups of populations within each region. The variation in capsule traits would support the idea of refugial survival at the Norwegian coast, but not that in seed shape.Maybe the most important factor influencing the dispersal ability and extent of the distribution area of P. radicatum is a change habitat conditions. Possibly open, stony, sparsely vegetated areas, left by the retreated ice-sheet restricted the previously more widely distributed populations during the post-glacial Hypsithermal. Hence, the differentiation pattern may reflect post-glacial events. Similarities in capsuleand seed traits between Icelandic and Scandinavian P. radicatum support mainly the hypothesis of survival on a former North Sea continent, followed by an immigration to Scandinavia, Iceland and the Faeroes.

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