Latitudinal origins of Fragaria vesca show adaptive variation in phenological, morphological and ecophysiological leaf traits associated with winter climate

Ongoing climate change is affecting vascular plants, but it is uncertain how plant species will react to the environmental changes, and therefore detailed understanding of adaptive phenotypic variation is needed. Woodland strawberry (Fragaria vesca L.) has a large geographical range, thus having great phenotypic variation and ability to adapt to different climates. One adaptive trait that allows F. vesca to continue photosynthesis through an extended growing season is the production of two morphologically distinct sets of leaves - summer leaves, produced in the spring and summer, and winter leaves produced in the autumn. However, to date it was unknown whether F. vesca genotypes from warmer European countries produce winter leaves, and whether they could survive cold winter conditions. To test for local adaptation in F. vesca, we studied variation in phenology, morphology and ecophysiology among ten European F. vesca genotypes from populations extending over the natural latitudinal range of the species. All genotypes survived a harsh winter in a common garden in southern Finland and produced winter leaves. These leaves acclimated well to the winter climate, as the maximum ca-pacity of photosystem II (Fv/Fm) remained high from late autumn to spring despite low temperatures. We found a latitudinal pattern in phenology with the northern European genotypes producing their first winter leaves earlier than the genotypes of southern European origin. This indicates that winter leaf phenology and climate accli-mation are under genetic control and express local adaptation. In contrast, cessation of stolon production in the autumn did not show a latitudinal cline. Our finding that local adaptation causes clear differences among populations in functional traits in F. vesca provides a foundation for future studies to explore underlying genetic variation and molecular processes affecting these traits that might improve the resilience of plant populations in a changing climate.