Plant Diversity ›› 2020, Vol. 42 ›› Issue (03): 198-208.DOI: 10.1016/j.pld.2020.05.003

• Articles • Previous Articles    

New insights into the evolutionary history of Megacodon: Evidence from a newly discovered species

Jun-Chu Penga,b,c, Xiang-Guang Mab, Yue-Hua Wanga, Hang Sunb   

  1. a School of Life Sciences, Yunnan University, Kunming 650091, China;
    b CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China;
    c University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-04-06 Revised:2020-05-28 Online:2020-06-25 Published:2020-07-15
  • Contact: Hang Sun
  • Supported by:
    This study was supported by the Key Projects of the Joint Fund of the National Natural Science Foundation of China (U1802232), the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502). Thanks to Si-Rong Yi (Chongqing Three Gorges Medical College) and Wei Zhang for providing valuable distribution information, Sha Wen for her line drawing of the new species, Ti-Cao Zhang (Yunnan University of Chinese Medicine) and Yan-Ting Hu for useful advice on RNA-seq analysis. We also appreciate the help of Jian Wen Zhang, Zhuo Zhou, Yang Niu, Yi Yang, Lu Sun, Zhe Chen, Bo Xu (Southwest Forestry University), Hong-Liang Chen, Li-Shen Qian, and Yong-Zeng Zhang during fieldwork.

Abstract: Megacodon is an ideal genus to study speciation and ecological adaptation in the Sino-Himalayan region. The genus contains two species distributed at different elevations and in two separate areas. However, studies of this genus have long been impeded by a lack of fieldwork on one of its species, Megacodon venosus. In this study, we collected specimens of two Megacodon species and found an extraordinary new species of Megacodon in Lushui county of north-west Yunnan province, which we have since named Megacodon lushuiensis. We propose new species based on both morphological and molecular evidence. The finding of this new species emphasized the importance of ecological divergence in the divergence of Megacodon stylophorus and its parapatric low-elevation Megacodon species. To identify genetic determinants that underlie adaptations to different elevations, we characterized transcriptomes of the new species M. lushuiensis, which is distributed at low elevations, and M. stylophorus, which is distributed at high elevations. Comparative transcriptome analysis identified 8926 orthogroups containing single-copy genes, and 370 orthogroups containing significantly positively selected genes. The set of positively selected genes was enriched into 25 Gene Ontology terms, including “response to water deprivation”, “response to osmotic stress”, and “cellular response to external stimulus”. Our results provide new insights into how ecological adaptation and speciation occurred in Megacodon and highlight the role of heterogeneous habitats in the speciation of plants in the Sino-Himalayan region.

Key words: Megacodon, Transcriptome, New species, Evolutionary pattern, Positive selection