Abstract
Fokienia hodginsii is a Tertiary relict conifer of the monotypic genus Fokienia (Cupressaceae s.l.). Currently, the species is distributed in southern China, northern Vietnam, and northern Laos and listed as a “near threatened” species by the IUCN. In this study, a total of 427 individuals of F. hodginsii were sampled from China and Vietnam to characterize its genetic diversity and population differentiation. Based on the profiles of 12 simple sequence repeat (SSR) markers, we observed a high level of genetic diversity in F. hodginsii at the species level (H e =0.635), albeit slightly lower than that of its sister species Chamaecyparis obtusa. Signals of bottleneck events were detected in the populations GXDMS, GXHJ, V‐PXB, and V‐HB, probably due to Pleistocene glaciations or overexploitation in recent years. Pronounced genetic differentiation (F st = 0.157) was found in this species. The inbreeding index (F is = 0.176 ± 0.024) indicated that F. hodginsii has a mixed mating system. Significant correlation was found between the pairwise genetic differentiation and geographic distance (r = 0.882, p = 0.01), suggesting that genetic differentiation among the populations follows the model of isolation by distance (IBD). STRUCTURE analysis and principal coordinate analysis revealed that these populations were divided into four groups: the western China group located mainly in the Yunnan–Guizhou Plateau, the central China group located mostly in the Luoxiao Mountains and Nanling Mountains, the eastern China group located in the Wuyi Mountains and the Vietnam group containing two populations in Vietnam. The different terrains and elevations of populations may be the most likely factors leading to the differentiation between the western China group and the central China group, while the geographic isolation caused by the lack of appropriate habitats may greatly contribute to the differentiation between the central China group and the eastern China group. Based on the results, some conservation suggestions for this species are provided, such as establishing seed orchards and multiple nature reserves.
Highlights
Under current rapid global climate change, many endemic species are facing a high risk of extinction due to limited natural ranges re‐ sulting from genetic stochasticity or demographic, environmental, or other factors (Caughley, 1994; Gitzendanner & Soltis, 2000; Lande, 1993)
We synthesized 108 simple sequence repeat (SSR) primers that were successfully amplified in F. hodginsii (Ding et al, 2017). Applying these SSR mark‐ ers, we aimed to investigate the levels of genetic diversity and pop‐ ulation structure of this species, which could provide some reliable information for the protection of this endangered species
The Spatial Analysis of Molecular Variance (SAMOVA) demonstrated the highest value of FCT (FCT = 0.25346, p < 0.05; Supporting Information Figure S1) when it divided all 24 populations into four groups as follows: the west‐ ern China group including the populations located in western China; the central China group in‐ cluding the populations located in central China (Luoxiao Mountains, Nanling Mountains, and adjacent areas); the eastern China group including the remaining populations, mostly in the Wuyi Mountains; and the last group including two populations in Vietnam
Summary
Under current rapid global climate change, many endemic species are facing a high risk of extinction due to limited natural ranges re‐ sulting from genetic stochasticity or demographic, environmental, or other factors (Caughley, 1994; Gitzendanner & Soltis, 2000; Lande, 1993). Fossil records show that Fokienia was widely distributed in the Northern Hemisphere in ancient periods: fossils in forms with foliage and attached seed cones of Fokienia were re‐ ported from the Paleocene in Saskatchewan, central Canada (McIver & Basinger, 1990); the Oligocene in Jilin, northeastern China (Guo & Zhang, 2002); and the Miocene in Zhejiang, eastern China (He, Sun, & Liu, 2012) This genus is currently distributed in only south‐ ern China, northern Vietnam, and northern Laos (Zheng & Fu, 1978). Applying these SSR mark‐ ers, we aimed to investigate the levels of genetic diversity and pop‐ ulation structure of this species, which could provide some reliable information for the protection of this endangered species
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