Climatic adaptation and ecological divergence between two closely related pine species in Southeast China

Climatic selection contributes greatly to local adaptation and intraspecific differentiation, but this kind of selection could have also promoted interspecific divergence through ecological speciation. In this study, we examined genetic variation within and between two closely related pine species, Pinus massoniana and Pinus hwangshanensis. These two species occur in Southeast China and exhibit contrasting ecological preferences, although hybrids are formed where their distributions overlap. We sampled 26 populations of the two species across their distributional ranges and sequenced 25 climate-related candidate genes and 12 reference loci, assumed not to be related to climatic selection. More than half of the 25 candidate genes (17) showed signals of recent and/or ancient selection, as indicated by one or several robust tests at different evolutionary timescales, while selection signals were only detected at three of the 12 reference loci. The signals of recent selection were species s...