Data from: Identifying refugia from climate change using coupled ecological and genetic data in a transitional Mediterranean-temperate tree species

Populations occurring in areas of overlap between the current and future
distribution of a species are particularly important because they can
represent “refugia from climate change”. We coupled ecological and
range-wide genetic variation data to detect such areas and to evaluate the
impacts of habitat suitability changes on the genetic diversity of the
transitional Mediterranean-temperate tree Fraxinus angustifolia. We
sampled and genotyped 38 natural populations comprising 1006 individuals
from across Europe. We found the highest genetic diversity in western and
northern Mediterranean populations, as well as a significant west-to-east
decline in genetic diversity. Areas of potential refugia that correspond
to approximately 70% of the suitable habitat may support the persistence
of more than 90% of the total number of alleles in the future. Moreover,
based on correlations between Bayesian genetic assignment and climate,
climate change may favour the westwards spread of the Black Sea gene pool
in the long term. Overall, our results suggest that the northerly core
areas of the current distribution contain the most important part of the
genetic variation for this species and may serve as in situ macrorefugia
from ongoing climate change. However, rear-edge populations of the
southern Mediterranean may be exposed to a potential loss of unique
genetic diversity owing to habitat suitability changes unless populations
can persist in microrefugia that have facilitated such persistence in the
past.