engleski

Natural selection drives parallel divergence in the mountain plant Heliosperma pusillum s.l.

We investigated morphological and ecological differentiation and its adaptive significance in six pairs of alpine and independently evolved montane populations of Heliosperma pusillum s.l. to explore the role of natural selection vs. genetic drift during early phases of divergence. Therefore, we tested whether environmental conditions, characterised by vegetation surveys and temperature measurements, and morphology of alpine and montane populations differ in parallel across six population pairs. By reciprocal transplantation experiments in natural environments and in climate chambers we compared fitness of native vs. non-native individuals. Alpine and montane populations differed in environmental conditions and morphology in each pair. Morphological differentiation occurred in parallel and correlated with environmental, but not with Nei ´s genetic distances. In both environments, native individuals had higher establishment success and size. Hence, differentiation of independently evolved montane populations is strongly influenced by natural selection and adaptation likely occurs in parallel in response to drought and altitude, in montane and alpine populations respectively. Our study system exemplifies rapid, parallel evolution of ecotypes leading to morphologically and ecologically strongly divergent, though fully interfertile, ecotypes.

adaptation, ecological differentiation, ecotypes, Heliosperma pusillum s.l., parallel evolution, reciprocal transplantations

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