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Front. Genet. | doi: 10.3389/fgene.2019.01238

Population differentiation and demographic history of the Cycas taiwaniana complex (Cycadaceae) endemic to South China as indicated by DNA sequences and microsatellite markers

 Xinhui Wang1, 2, Jie Li1, Limin Zhang1, Ziwen He3, Qiming Mei1,  Xun Gong4 and  Shuguang Jian1*
  • 1Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden (CAS), China
  • 2University of Chinese Academy of Sciences, China
  • 3Sun Yat-sen University, China
  • 4Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, China

Historical geology, climatic oscillations, and seed dispersal capabilities are thought to influence the population dynamics and genetics of plants, especially for distribution-restricted and threatened species. Investigating the genetic resources within and among taxa is a prerequisite for conservation management. The Cycas taiwaniana complex consists of six endangered species that are endemic to South China. In this study, we investigated the relationship between phylogeographic history and the genetic structure of the C. taiwaniana complex. To estimate the phylogeographic history of the complex, we assessed the genetic structure and divergence time, and performed phylogenetic and demographic historical analyses. Two chloroplast DNA intergenic regions (cpDNA), two single-copy nuclear genes (SCNGs), and six microsatellite loci (SSR) were sequenced for 18 populations. The SCNG data indicated a high genetic diversity within populations, a low genetic diversity among populations, and significant genetic differentiation among populations. Significant phylogeographical structure was detected. Structure and phylogenetic analyses both revealed that the 18 populations of the C. taiwaniana complex have two main lineages, which were estimated to diverge in the Middle Pleistocene. We propose that C. fairylakea was incorporated into C. szechuanensis and that the other populations, which are mainly located on Hainan island, merged into one lineage. Bayesian Skyline Plot analyses revealed that the C. taiwaniana complex experienced a recent decline, suggesting that the complex probably experienced a bottleneck event. We infer that the genetic structure of the C. taiwaniana complex has been affected by Pleistocene climate shifts, sea-level oscillations, and human activities. In addition to providing new insights into the evolutionary legacy of the genus, the genetic characterizations will be useful for the conservation of Cycas species.

Keywords: Cycas taiwaniana complex, genetic diversity, Phylogeographic structure, Population Dynamics, conservation

Received: 08 Jul 2019; Accepted: 08 Nov 2019.

Copyright: © 2019 Wang, Li, Zhang, He, Mei, Gong and Jian. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Shuguang Jian, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden (CAS), Guangzhou, China,