Genetic Structure Of Chinese Populations Of Pelophylax Nigromaculata And Interspecific Genetic Variations Between Chinese Populations Of P.nigromaculata And P. Plancyi

This thesis includes four chapters:1. The studies on biology of Pelophylax nigromaculata, including morphology, classification, physiology, biochemistry, genetics and molecular biology are reviewed in the first chapter.2. Chapter 2 introduces concept, application, molecular markers and current status of molecular phylogeography.3. Sequences of the 5' end of the mitochondrial control region for 112 individuals of Pelophylax nigromaculata from twelve local populations in Chinese mainland were obtained. The aligned 685 bp fragments of the 5' CR include 111 variable sites. Sixty-seven haplotypes were identified. Most of the haplotypes are confirmed to local populations, only 7 of the 67 are shared among a few local populations. The overall species haplotype diversity was quite high (h = 0.98?.005), and the nucleotide diversity was also high ( = 0.0303?.0029). The high haplotype diversity and nucleotide diversity were corresponding to very large population size and extensive distribution of Pelophylax nigromaculata in Palaearctic Region and Oriental Region. Reconstructed phylogenetic relationships among the local populations based on neighbor joining algorithm suggested that the haplotypes of Jiling and Liaoning populations representing northeastern region have a sister relationship with other local populations representing Chinese mainland. The analysis of molecular variance (AMOVA) showed a significant population subdivision between Jiling and Liaoning populations representing northeastern group and other 10 local populations representing mainland group. The pairwise Fst values also suggested a significant genetic subdivision between the northeastern group and mainland group. The nucleotide divergenceindices also supported the above viewpoint. The most possible cause of the significant genetic subdivision between the two groups was referred to the effect of Quaternary glaciation. The possible reasons for the lack of obvious geographic structure on the whole in the mainland group and the genetic differentiation in some local populations of the mainland group were also discussed.4. Interspecific variations of sequence of 5' end of the mitochondrial control region (5'CR) and cytochrome b gene (cyt b) between Pelophylax nigromaculata and Pelophylax plancyi plancyi were studied. Six hundred and eighty-five bp sequences of partial 5'CR of 121 individuals from nigromaculata and 8 individuals from plancyi, 686 bp sequences of partial cyt b of 17 individuals from nigromaculata and 4 individuals from plancyi were obtained. The results showed that the interspecific genetic divergence between Pelophylax nigromaculata and Pelophylax plancyi is very low, and is even lower than that between northeastern group and mainland group in Pelophylax nigromaculata. How to explain the low genetic divergence between the two species? We suggest this might be referred to the close relationship between the two species, and the relatively rapid genetic differentiation occurred in the northeastern populations of Pelophylax nigromaculata as we discussed in the previous chapter. Introgression hybridization between Pelophylax nigromaculata and Pelophylax plancyi might be another and the most possible cause contributing to the low interspecific genetic divergence of the two species.