Résumé
Species range shifts in response to climate and land use change are
commonly forecasted with species distribution models based on species
occurrence or abundance data. Although appealing, these models ignore the
genetic structure of species, and the fact that different populations
might respond in different ways due to adaptation to their environment.
Here, we introduced ancestry distribution models, i.e., statistical models
of the spatial distribution of ancestry proportions, for forecasting
intra-specific changes based on genetic admixture instead of species
occurrence data. Using multi-locus genotypes and extensive geographic
coverage of distribution data across the European Alps, we applied this
approach to 20 alpine plant species considering a global increase in
temperature from 0.25°C to 4°C. We forecasted the magnitudes of
displacement of contact zones between plant populations potentially
adapted to warmer environments and other populations. While a global trend
of movement in a northeast direction was predicted, the magnitude of
displacement was species-specific. For a temperature increase of 2°C,
contact zones were predicted to move by 92 km on average (minimum of 5 km,
maximum of 212 km), and by 188 km for an increase of 4°C (minimum of 11
km, maximum of 393 km). Intra-specific turnover – measuring the extent of
change in global population genetic structure – was generally found to be
moderate for 2°C of temperature warming. For 4°C of warming, however, the
models indicated substantial intra-specific turnover for ten species.
These results illustrate that, in spite of unavoidable simplifications,
ancestry distribution models open new perspectives to forecast population
genetic changes within species, and complement more traditional
distribution-based approaches.