J Syst Evol

• Research Article •    

Phylogenetic and molecular dating analyses of Chinese endemic genus Dipelta (Caprifoliaceae) based on nuclear RAD-Seq and chloroplast genome data

Yanan Cao1*, Menghao Wang1, Hang Ran1, Bin Tian3, Luxian Liu4, Qingnan Wu1, Yanyan Liu1, Hongwei Wang1*, Shanshan Zhu2*   

  1. 1 College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China;
    2 School of Marine Sciences, Ningbo University, Ningbo, Zhejiang 315211, China;
    3 Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China;
    4 Laboratory of Plant Germplasm and Genetic Engineering, School of Life Sciences, Henan University, Kaifeng, 475001, P.R. China
    Corresponding authors: Cao Yanan,caoyn47@163.com; Zhu Shanshan,21407009@zju.edu.cn; Wang Hongwei, whwcas@163.com.
  • Received:2024-01-09 Accepted:2024-03-27 Published:2024-04-12

Abstract: Dipelta Maxim. (Caprifoliaceae) is a Tertiary relic genus endemic to China, which includes three extant species, D. floribunda, D. yunnanensis and D. elegans. Recent progress in the systematics and phylogeographics of Dipelta has greatly broadened our knowledge about its origin and evolution, however, conflicted phylogenetic relationships and divergence times have been reported and warrant further investigation. Here, we utilized chloroplast genomes and population-level genomic data (RAD-SNPs) to evaluate the interspecific relationships, population genetic structure and demographic histories of this genus. Our results confirmed the sister relationship between D. elegans and the D. yunnanensis-D. floribunda group, but with cyto-nuclear phylogenetic discordance observed in the latter. Coalescent simulations suggested that this discordance might be attributed to asymmetric “chloroplast capture” through introgressive hybridization between the two parapatric species. Our fossil-calibrated plastid chronogram of Dipsacales and the coalescent modeling based on nuclear RAD-SNPs simultaneously suggested that the three species of Dipelta diversified at the late Miocene, which may be related to the uplift of the eastern part of Qinghai-Tibet Plateau (QTP) and adjacent southwest China, and increasing Asian interior aridification since the late Miocene; while in the mid- Pleistocene, the climatic transition and continuous uplift of the QTP, triggered allopatric speciation via geographical isolation for D. floribunda and D. yunnanensis regardless of bidirectional gene flow. Based on both plastid and nuclear genome-scale data, our findings provide the most comprehensive and reliable phylogeny and evolutionary histories for Dipelta and enable further understanding of the origin and evolution of floristic endemisms of China.

Key words: endemism, phylogenomics, phylogenetic discordance, molecular dating, coalescent modeling, introgressive hybridization