Introduction
I. Bufo gargarizansspecies complex
The Asiatic toad, Bufo
gargarizans , (Cantor, 1842), is distributed in China, Russia, North
Korea, South Korea, and Japan (Miyako and Ryukyu Islands). Bufo
gargarizans is currently classified as Least Concern in the IUCN Red
List because of its large habitat range, but it is likely to be
classified as a risk category if a threat occurs (IUCN, 2019). This
species has had a complicated taxonomic history (Hu, Jiang & Tian,
1984; Huang, Jin & Cai, 1990; Macey et al., 1998; Liang, Changyuan &
Jianping, 2010), with several species being recognized as distinct or
the same species as B. gargarizans (Fu et al., 2005). Some
molecular studies considered B. andrewsi , B. minshanicus ,
and B. tibetanus to be synonyms of B. gargarizans , whileB. bankorensis is treated as a distinct species (Chen et al.,
2013; Yu, Lin & Weng, 2014; Tong & Wo, 2017; Frost, 2020).
Genetic studies of B. gargarizans have provided insight into its
evolutionary history. An allozyme-based study of B. gargarizanscomparing individuals from Korea and China confirmed a clear genetic
difference between the two regions (Yang et al., 2000). Zhan and Fu
(2011) performed a multilocus molecular study using both mitochondrial
DNA (mtDNA) and nuclear DNA (nuDNA), and sampled B. gargarizansthroughout China covering four major geographic regions (West [W],
Central [C], Southeast [SE], Northeast [NE]); they recovered
seven clades not differentiated based on geography (e.g., Clade A
included samples from the W, C, and NE). The most recent study (Borzée
et al., 2017) used two mtDNA markers (control region, NADH dehydrogenase
2 [ND2 ]) to study the phylogeography of B. gargarizansin China and South Korea, and found a clade of individuals from South
Korea and across China. Zhan and Fu (2011) and Borzée et al. (2017) have
contributed to our understanding of the evolutionary history of B.
gargarizans , but both had reasonable limitations in their study design.
To clarify the genetic status of the B. gargarizans species
complex, we combine the strengths of previous studies by including
comprehensive geographic sampling and multiple molecular loci.