Hyrcanian forests—Stable rear‐edge populations harbouring high genetic diversity ofFraxinus excelsior,a common European tree species

Hyrcanian forests, part of the Caucasus biodiversity hotspot and located near the southern Caspian Sea, harbor significantly higher genetic diversity in common ash (Fraxinus excelsior) compared to European populations. This study reveals that Hyrcanian populations exhibit stable rear-edge dynamics with diverse genetic markers, including EST-SSRs, suggesting their potential as a critical reservoir for species adaptation amid global climate change and ash dieback. Population divergence between European and Hyrcanian populations was traced back to the Pleistocene epoch, with evidence of recent population size reduction across all studied regions. Additionally, substructure within Hyrcanian forests was identified, featuring distinct western-central and eastern subclusters, along with two new plastid haplotypes in the easternmost populations. These findings underscore the evolutionary significance of the Hyrcanian forests for both F. excelsior and potentially other European tree species.

Erichsen, E. O., Budde, K. B., Sagheb‐Talebi, K., Bagnoli, F., Vendramin, G. G., & Hansen, O. K. (2018). Hyrcanian forests—Stable rear‐edge populations harbouring high genetic diversity ofFraxinus excelsior,a common European tree species. Diversity and Distributions, 24(11), 1521–1533. Portico. https://doi.org/10.1111/ddi.12783