Phylogeographical Study of Camellia japonica Inferred from AFLP and Chloroplast DNA Haplotype Analyses

摘要

Intraspecific genetic variation provides the information on the distributional pattern of plant species by inducing local adaptation, range shifts, and range reduction. Here, genetic variation of amplified fragment length polymorphism (AFLP) and three chloroplast DNA (cpDNA) regions (atpI-atpH, trnD-psbM, and trnT-L) is investigated in 37 populations of Camellia japonica to assess the genetic diversity and population structure. We also infer the phylogeographical history of C. japonica distributed in South Korea, Japan (Kyushu and Okinawa), and Taiwan of East Asia. The AFLP results reveal high levels of genetic diversity in C. japonica across East Asia. At the regional level, the Kyushu populations display the highest level of genetic variation, whereas the mainland populations of South Korea exhibit the lowest level of variation. Our results show trends of loss of genetic diversity along with latitude. On the basis of 154 polymorphic sites of the combined three cpDNA regions, 11 haplotypes (A-K) were identified across the East Asian C. japonica populations. Haplotypes A-C are dominant and widespread in South Korea and Japan, while Haplotypes G, I, and J in Taiwan. In addition, five haplotypes (A, B, D-F) are exclusively occur in South Korea/Japan and five (G-K) are in Taiwan. Our molecular dating analysis estimates the age of initial diversification of C. japonica haplotypes in the late Tertiary. The phylogeographic patterns of C. japonica coupled with molecular dating suggest vicariance as key mechanism for initial diversification between South Korea/Japan and Taiwan. In contrast, the haplotypes of Japan are shared with those of South Korea indicating that they had insufficient time to form population structures at the regional level.