J Syst Evol

• Research Articles •    

Genomic analyses reveal natural selection on reproduction related genes between two closely related Populus (Salicaceae) species

Yang Tian1,2†, Shu‐Yu Liu1, Pär K. Ingvarsson3, Dan‐Dan Zhao1, Li Wang1, Baoerjiang Abuduhamiti4, Jin‐Feng Cai2, Zhi‐Qiang Wu5, Jian‐Guo Zhang1,2*, and Zhao‐Shan Wang1,2†*   

  1. 1 State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China 100091.
    2 Collaborative Innovation Center of Sustainable, Forestry in Southern China, Nanjing Forestry University, Nanjing, China 210037.
    3 Linnean Centre for Plant Biology, Department of Plant Biology, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.
    4 Forestry Research institute of Altay region, Altay, Xinjiang, China 836500.
    5 Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China. 518120

    These authors have contributed equally to this work
    *corresponding authors: Zhaoshan Wang, w@caf.ac.cn; Jianguo Zhang, zhangjg@caf.ac.cn.
  • Received:2022-04-08 Accepted:2022-08-23 Online:2022-08-28


Identifying the factors that cause reproductive isolation and their relative importance in species divergence is crucial to our understanding of speciation processes. In most species, natural selection is commonly considered to play a large role in driving speciation. Based on whole genome re-sequencing data from 27 Populus alba and 28 Populus adenopoda individuals, we explored the factors related to reproductive isolation of these two closely related species. The results showed that the two species diverged ~5–10 million years ago (Ma), when the Qinghai–Tibet Plateau reached a certain height and the inland climate of the Asian continent became arid. In highly differentiated genomic regions, the relative divergence (FST) and absolute divergence (dxy) were significantly higher than the genomic background, θπ and shared polymorphisms decreased whereas fixed differences increased, which indicated that natural selection played a key role in the reproductive isolation of the two species. In addition, we found several genes that were related to reproduction that may be involved in explaining the reproductive isolation. Using phylogenetic trees resolved from haplotype data of Populus tomentosa and P. adenopoda, the maternal origin of P. tomentosa from P. adenopoda was likely to be located in Hubei and Chongqing Provinces.

Key words: Populus alba, P. adenopoda, P. tomentosa, whole genome re-sequencing, demographic histories, natural selection