Quercus acutissima (sawtooth oak) is a dominant species occupying a wide range of environmental conditions in subtropical and warm temperate zones in China. Owing to its high ecological and economic value, it has been listed as a precious timber species in China. Populations of this species can persist across large temperature and precipitation ranges. However, the genetic‐based climate adaptation in Q. acutissima remains unclear. 

In a study published in Journal of Systematics & Evolution, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) combined a common garden experiment with range‐wide population genomics analyses to infer the demographic history and characterize patterns of local adaptation in the sawtooth oak.  

The researchers surveyed approximately 8% of the oak genome and recovered 55 361 single nucleotide polymorphisms (SNPs) from sampled populations of Q. acutissima. Those sites included a balanced proportion of both genic and non‐coding regions. Genetic structure and principal component analysis of these populations indicated an east‐west split. 

Coalescent‐based model simulations inferred a late Pleistocene divergence in Q. acutissima between the east and west groups as well as subsequent preglaciation population expansion events. 

Moreover, the genetic and phenotypic analyses revealed a joint effect of geography and environment on Q. acutissima. 

"To our knowledge, this study is the first to attempt to combine a genome scan and phenotype evaluation in a common garden in an Asian subtropical oak species; it will provide a valuable study system to compare with temperate oaks in North America and Europe", said Dr. GAO Jie, first author of the study. 

The approach, which combined a common garden experiment with landscape genomics data, validated the hypothesis of local adaptation of the long‐lived oak tree of subtropical China.