4.2. Distribution of S. triangularis and S.
collaris in China
Sibynophis triangularis was originally described based on a
single specimen from Thailand (Taylor & Elbel, 1958). Although
initially considered a subspecies of S. collaris , it was
subsequently elevated to a separate species, i.e., S.
triangularis (Taylor, 1965). At present, this species is known to occur
in Thailand and Cambodia (Stuart, Sok, & Neang, 2006; Uetz et al.,
2022; Wallach et al., 2014). However, our molecular phylogenetic
reconstruction revealed that a particular sample (FMNH 263023,
Cambodia), previously identified as S. triangularis (Stuart et
al., 2006), formed a well-supported clade (C) with specimens from
Vietnam, Myanmar, and China (southern
and northwestern Yunnan). Hence, we confirm that clade C represents the
species S. triangularis , which is newly reported in China and
Myanmar. Currently, S. triangularis is only known to occur in
Fugong and Cangyuan in Yunnan of China.
Our results identified clade B as sister to clade C, representingS. collaris based on geographical origin. Unexpectedly, sample
CAS 240150 collected from Myanmar and originally identified as S.
collaris in Chen et al. (2013) formed a distinct mtDNA lineage from
clade B, with genetic distances of 8.3% (cyt.b -based) and 7.9%
(ND2-based), respectively (Table 2; Fig. 2). These findings suggest that
this specimen was misidentified and may represent an undescribed taxon.
Thus, further examination of this specimen is required. In addition, in
a previous large-scale systematic study of Chinese snakes, Li et al.
(2020) identified one specimen (CHS 244) from Honghe, southern Yunnan,
China, as S. collaris , and two specimens (CHS 879 and CHS 880)
from Motuo, Xizang, China, as S. chinensis . Our results showed
the first specimen was nested within the clade A and the latter two
positioned in the clade B. Thus we concluded that these samples were
misidentified, with the former being S. grahami and the latter
two being S. collaris .
Zhao and Yang (1997), Zhao et al. (1998), Zhao (2006), and Yang and Rao
(2008) proposed that S. collaris is distributed in southern
Xizang and northwestern Yunnan in China. Based on our molecular
phylogenetic analyses, however, several specimens collected from
northwestern Yunnan, which is geographically close to Motuo, Xizang,
were identified as S. grahami and S. triangularis (Fig.
2). Thus, it is most like that S. collaris is endemic to Motuo in
Xizang, with no occurrence in Yunnan.