4.1 Systematics of S. chinensis
Sibynophis chinensis is widely distributed in China. Here, the mtDNA-based phylogeny indicated that S. chinensis was composed of clades A and D. Clade D consisted of specimens from Vietnam and Southwest, Central, and Southeast China, corresponding to the S. c. chinensis subspecies. Clade A consisted of specimens from Yunnan, Guizhou, and Sichuan, which are the distribution regions of the S. c. miyiensis and S. c. grahami subspecies; three specimens (YBU 15152, GP 10544, and KIZ 028322) attributed to S. c. miyiensiswere nested within the other specimens, thereby rendering S. c. grahami non-monophyletic. Therefore, based on priority rule of nomenclature we concluded that clade A should be represented by S. c. grahami , and S. c. miyiensis should be considered a synonym of S. c. grahami .
Unexpectedly, although clades A and D were highly supported, neither formed a monophyletic lineage (Fig. 2). The genetic distance between the two clades was 12.6% (cyt.b -based), which exceeds that between certain species (e.g., 9.4% between S. subpunctatus and S. bistrigatus ) (Table 2). In addition, network analyses revealed that the two clades did not share any nDNA haplotype. These findings suggest that both clades represent two distinct species, i.e., clade A representsS. grahami and clade D represents S. chinensis .
Given the taxonomic revision of S. chinensis (sensu lato ), the distribution of S. grahami should be redefined accordingly. Thus, based on previous records (Zhao, 2006; Zhao et al., 1998) and our data, we conclude that S. grahami is present in southwestern Sichuan, Yunnan, and Guizhou in China.