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Range-wide patterns of genetic variation in Fraxinus angustifolia and the potential effects of climate change on its genetic diversity

The potential for adaptation to changing environment is largely dependent on current genetic variation across species’ ranges. To identify spatial patterns of genetic variation in Mediterranean tree Fraxinus angustifolia and to investigate the effects of potential range shifts under climate change on species genetic diversity, we applied a multidisciplinary approach by combining population genetics based on nuclear microsatellite markers, Bayesian clustering and Ecological niche modelling (ENM) methods. We used 38 natural populations across species’ European range. We identified two main genetic groups in Europe with a clear West - East pattern of population structure. We revealed centres of highest genetic diversity in West and North Mediterranean populations compared to East and South Mediterranean populations as well as significant longitudinal West - East geographical cline of decreasing genetic diversity. As expected, ENM predicted northwards range shift of F. angustifolia in response to warming climate, while detected areas of habitat stability may be considered as in situ refugia from 21st century climate change. Our results suggest that predicted climate changes, which are expected to be most pronounced in the south Mediterranean, combined with low migration rates in trees, may cause a partial loss of the overall species’ genetic diversity.

climate change; genetic variation; Fraxinus angustifolia; niche modelling

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