1 INTRODUCTION
Species diversity is central to biodiversity. Exploration of species
diversity and identification of species distribution boundaries are
pivotal to the preservation and management of biodiversity. The
accumulation of multi-locus data and development of related analytical
technologies have greatly advanced our understanding of cryptic species
diversity. In recent decades, considerable progress has been made in the
phylogeny of Asian snakes. Notably, various systematic issues have been
addressed (Guo, Zhu, Liu, Wang, & Nguyen, 2020; Hou et al., 2021; Liu
et al., 2021; Poyarkov et al., 2022) and an increasing number of new
taxa have been described (Hou et al., 2021; Liu, Zhong, Wang, Liu, &
Guo, 2018; Ren, Jiang, Huang, David, & Li, 2022). However, in
comparison to well-studied common snake groups, such as Hebiusand Lycodon (Guo et al., 2013; Guo et al., 2014; Hou et al.,
2021; Ren et al., 2022), little attention has been paid to rare snake
species, such as those in the genus Sibynophis .
The family Sibynophiidae is comprised of only two genera, including the
non-venomous genus Sibynophis . These snakes are characterized by
their small body size, loose attachment of their dentary to the
articular bone, and the presence of numerous small maxillary teeth of
uniform size (Pope, 1935). Currently, nine species are recognized withinSibynophis , with primary distribution in South and Southeast Asia
(Uetz, Freed, Aguilar, & Hošek, 2022; Wallach, Williams, & Boundy,
2014). Two species, S. collaris and S. chinensis , are
known to occur in China (Wang et al., 2020; Zhao, 2006).Sibynophis chinensis was initially described based on a
sole specimen from Yichang, Hubei, China (Günther, 1889), but is now
known to occur in China, Korea, and Vietnam (Wallach et al., 2014). In
China, the species exhibits broad distribution, ranging from southern
Xizang in the west to Jiangsu in the east (Zhao, 2006). Three subspecies
are currently recognized (Zhao, 2006; Zhao, Huang, & Zong, 1998),
including S. c. chinensis , S. c. grahami , and S. c.
miyiensis . In addition to the nominal species, which broadly occurs in
Southwest, Central, and East China, S. c. miyiensis is endemic to
Southwest Sichuan and Northwest Yunnan, while S. c. grahami is
endemic to northeastern Yunnan and Guizhou (Zhao et al., 1998; Zhao &
Yang, 1997). This taxonomical arrangement is followed by most authors
(Uetz et al., 2022; Wallach et al., 2014; Wang et al., 2020). The type
locality of S. collaris is in Assam, India (Gray, 1853), but the
species is restricted to Xizang and Yunnan in China (Zhao, 2006; Zhao et
al., 1998). Morphologically, the two species differ from one another by
number of supralabials and anterior temporal scales only (Zhao, 2006;
Zhao et al., 1998).
Due to their rare occurrence and elusive nature, few Sibynophisspecimens have been collected since their initial description and few
studies have been conducted on their biology, particularly their
systematics (Li et al., 2020; Pyron, Burbrink, & Wiens, 2013; Zaher et
al., 2019). Although Sibynophis species have been included in
certain phylogenetic studies (Chen et al., 2013; Li et al., 2020; Pyron
et al., 2013; Zaher et al., 2019), only a limited number of samples have
been examined. For example, Zaher et al. (2019) conducted a large-scale
molecular phylogenetic study of advanced caenophidian snakes, which
included five Sibynophis species, each with only one individual.
Thus, given the small number of species and specimens studied, the
diversity and evolution of the genus remain poorly understood.
Here, based on more extensive sampling, we explored species diversity of
the genus Sibynophis and revised the taxonomy and distribution
boundaries of each taxon within China.