Low genetic differentiation across an entire continent: the Scots pine paradox

Abstract

O_LIScots pine is the foundation species of diverse forested ecosystems across Eurasia and displays remarkable ecological breadth, occurring in environments ranging from temperate rainforests to arid tundra margins. Such expansive distributions can be favored by various demographic and adaptive processes and the interactions between them. C_LIO_LITo understand the impact of neutral and selective forces on genetic structure in Scots pine, we conducted range-wide population genetic analyses on 2,321 trees from 202 populations using genotyping-by-sequencing, reconstructed the recent demography of the species, and examined signals of genetic adaptation. C_LIO_LIWe found a high and uniform genetic diversity across the entire range (global FST 0.048), no increased genetic load in expending populations and minor impact of the last glacial maximum on historical population sizes. Genetic-environmental associations identified only a handful of SNPs significantly linked to environmental gradients. C_LIO_LIThe results suggest that extensive gene flow is predominantly responsible for the observed genetic patterns in Scots pine. The apparent missing signal of genetic adaptation is likely attributed to the intricate genetic architecture controlling adaptation to multi-dimensional environments. The panmixia metapopulation of Scots pine offers a good study system for further exploration into how genetic adaptation and plasticity evolve under gene flow and changing environment. C_LI