Genetic Diversity and Differentiation of Chinese Fir around Karst Landform in Guangxi

The karst geo-ecosystems are fragile environments. The largest karst region in the world is located in southwestern China, within which the Guangxi province is one of the main areas. Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), an evergreen species, is an important fast-growing timber tree in southern China. In the present study, we examined the genetic diversity and spatial genetic differentiation of Chinese fir in sampling localities around the karst landform region of Guangxi by genotyping 330 individuals from 11 sampling localities with 22 novel polymorphic microsatellite loci. High levels of gene flow have homogenized Chinese fir in Rongshui, Nandan, and Tiane sites, which are speculated to be the primary center of gene exchange and diversity for Chinese fir around the karst landform in Guangxi. Significant isolation by distance pattern was found among nine sampling localities. A moderate level of genetic differentiation (F-ST = 0.089, D-est = 0.139) between sampling localities was detected. Structure analysis divided Chinese fir into three subgroups (K = 3). With higher differentiation and less genetic variation than in the central population, marginal populations of Cangwu and Pubei were identified in the south of the karst landform. An effective conservation strategy focusing on the maintenance of genetic variation for marginal populations of the species was proposed.