The Historical Demography and Genetic Variation of the Endangered Cycas multipinnata (Cycadaceae) in the Red River Region, Examined by Chloroplast DNA Sequences and Microsatellite Markers

Abstract

Cycas multipinnata C.J. Chen & S.Y. Yang is a cycad endemic to the Red River drainage region that occurs under evergreen forest on steep limestone slopes in Southwest China and northern Vietnam. It is listed as endangered due to habitat loss and over-collecting for the ornamental plant trade, and only several populations remain. In this study, we assess the genetic variation, population structure, and phylogeography of C. multipinnata populations to help develop strategies for the conservation of the species. 60 individuals from six populations were used for chloroplast DNA (cpDNA) sequencing and 100 individuals from five populations were genotyped using 17 nuclear microsatellites. High genetic differentiation among populations was detected, suggesting that pollen or seed dispersal was restricted within populations. Two main genetic clusters were observed in both the cpDNA and microsatellite loci, corresponding to Yunnan China and northern Vietnam. These clusters indicated low levels of gene flow between the regions since their divergence in the late Pleistocene, which was inferred from both Bayesian and coalescent analysis. In addition, the result of a Bayesian skyline plot based on cpDNA portrayed a long history of constant population size followed by a decline in the last 50,000 years of C. multipinnata that was perhaps affected by the Quaternary glaciations, a finding that was also supported by the Garza-Williamson index calculated from the microsatellite data. The genetic consequences produced by climatic oscillations and anthropogenic disturbances are considered key pressures on C. multipinnata. To establish a conservation management plan, each population of C. multipinnata should be recognized as a Management Unit (MU). In situ and ex situ actions, such as controlling overexploitation and creating a germplasm bank with high genetic diversity, should be urgently implemented to preserve this species.

The distribution, diversity, and conservation status of Cycas in China

“…Based on Bayesian Skyline Plot, a scenario of population expansion was suggested for both C. revoluta and C. taitungensis (Chiang et al., ), which contrary to the contraction experience occurred on southeast Asia Cycas species (Feng, Zheng, & Gong, ; Feng, Liu, et al., ; Gong et al., ; Zheng et al., ). One possible reason for this contrast is the different evolutionary processes of both topography and species in history (Gong et al., ; Huang et al., ; Kizaki & Oshiro, ; Shaw & Huang, ).…”

“…For C. debaoensis, several measures have been recommended, including setting up nature reserves and protection stations, improving publicity and education, conducting research on fast reproduction, and strengthening government management (Xie et al, 2005). Gong et al (2015) have also laid out in situ and ex situ projects for C. multipinnata.…”

“…As a recently radiated lineage, some Cycas species in southwest China exhibit high genetic diversity at the species level, low genetic diversity within populations, and significant genetic differentiation among populations (Feng, Wang, & Gong, ; Gong et al., ; Liu, Zhou, & Gong, ; Zheng, Liu, & Gong, ). However, specific comparison concerning genetic variations of all the Cycas species in China has rarely been performed.…”

“…As a recently radiated lineage, some Cycas species in southwest China exhibit high genetic diversity at the species level, low genetic diversity within populations, and significant genetic differentiation among populations (Feng, Wang, & Gong, 2014;Gong et al, 2015;Liu, Zhou, & Gong, 2015;Zheng, Liu, & Gong, 2016 (Ma et al, 2013), displaying the highest proportion of the genus than any other plant groups (15/23, 65%) (Sun, 2013;Zheng et al, 2013). As human disturbance has severely disturbed Cycas populations and its habitats, multiple protective efforts have been made over the last decade (Luo, Tang, Huang, Liang, & Zhao, 2014;Zhan, Wang, Gong, & Peng, 2011).…”

Spatial and temporal genetic dynamics of the grasshopper Oedaleus decorus revealed by museum genomics

“…Understanding processes shaping the genetic variation in species through space and time is crucial in various fields of biology, ranging from informing conservation decisions (e.g., Inoue, Lang, & Berg, ; Mukesh, Sharma, Shukla, & Sathyakumar, ) and unraveling the demographic history of species (e.g., Gong et al., ; Tsuda, Nakao, Ide, & Tsumura, ; Vera Escalona, Habit, & Ruzzante, ) to disentangling key evolutionary processes (e.g., Capblancq, Després, Rioux, & Mavárez, ). Investigating genetic variation through space has proven valuable to unravel the role of environment in genetic divergence (Björklund, Alonso, & Edelaar, ; D'Amen, Zimmermann, & Pearman, ).…”