Synchronous effective population size changes and genetic stability of forest trees through glacial cycles.

Past environmental changes have shaped the demographic history and genetic diversity of natural populations, yet the timescale and strength of these effects have not been investigated systematically and simultaneously for multiple phylogenetically distant species. We10 performed comparative population genomic analyses and demographic inference for seven ecologically contrasting European tree species sampled across their ranges. While patterns of genetic diversity and differentiation were species-specific and best explained jointly by each species' geographic range and dispersal ability, ancient population expansion events were shared and synchronous across species. Effective population sizes increased or remained stable over15 time, indicating that despite major changes in their geographic ranges, major forest tree species have been remarkably genetically resilient to the environmental challenges of repeated glacial cycles