Phylogeographic study of theBufo gargarizansspecies complex, with emphasis on Northeast Asia

Abstract

We conduct a phylogeographic and population genetic study of the Asiatic toad ( Bufo gargarizans ) to understand its evolutionary history, and the influence of geology and climate. A total of 292 individuals from 94 locations were genotyped for two mitochondrial loci ( cytb , ND2 ) and five nuclear introns ( Sox9-2 , Rho-3 , CCNB2-3 , UCH-2 , and DBI-2 ), and we performed a suite of phylogenetic, population genetic, and divergence dating analyses. The phylogenetic trees constructed using mitochondrial loci inferred B. gargarizans being divided into two major groups: China mainland and Northeast Asia (Northeast China, Russia, and Korean Peninsula). As with previous studies of this species, we recover population genetic structure not tied to geographic region. Additionally, we discover a new genetic clade restricted to Northeast Asia that points towards the Korean Peninsula being a glacial refugium during the Pleistocene. The weak phylogeographic pattern of B. gargarizans is likely the result of multiple biological, anthropogenic, and historical factors – robust dispersal abilities as a consequence of physiological adaptations, human translocation, geologic activity, and glacial cycles of the Pleistocene. We highlight the complex geologic and climatic history of Northeast Asia and encourage further research to understand its impact on the biodiversity in the region.

From Gondwana to the Yellow Sea, evolutionary diversifications of true toads Bufo sp. in the Eastern Palearctic and a revisit of species boundaries for Asian lineages

“…Previous studies estimated the isolation of Bufo populations on the Korean Peninsula to date from the Pleistocene (Borzée et al, 2017;Lee et al, 2021), and our results confirm this pattern. However, additional samples from further east demonstrated the presence of a deeper segregation between the clades around the Yellow Sea, with B. gargarizans to the southwest and B. sachalinensis in septentrional Eastern Asia (Figure 6).…”

“…Instead, our results provided support to the combination of the three elements: vicariance of the western mainland clade, followed by long dispersal, and possible refugia in northeastern Asia during the last ice age. We detected a loss of genetic structure within B. gargarizans clades , possibly due to introgression resulting from the trade of the species over a millennium ( Lee et al, 2021 ). The recent segregation around the Yellow Sea, as shown by the species distribution models and migration pattern, also provides support to the delineation of a septentrional Asian Bufo clade associated with range shift toward northern latitudes.…”

“…Following multiple calls for a taxonomic revision and the various species descriptions and synonimization ( Matsui, 1986 ; Igawa et al, 2006 ; Borzée et al, 2017 ; Lee et al, 2021 ), we suggest the following updates to the taxonomy. It is to be noted that we do not describe any new species as a long list of valid former names is available ( Supplementary file 1I , Figure 1—figure supplement 1 ).…”

“…The presence of two individuals within the range of B. gargarizans showing 95% and 87% admixtures with the B. sachalinensis clade ( Supplementary file 1F , Figure 4D ) is likely the result of human-led translocations. Bufo toads have been used for traditional Chinese medicine for more than a millennium ( Zhan et al, 2020 ; Lee et al, 2021 ) and gene flow toward the regions relying on the genus for medicine may actually reveal the directionality of the trade, and escape of individuals at markets, rather than natural dispersal.…”

“…The distribution of B. gargarizans has similarly been strongly influenced by human activities, particularly through the traditional medicine trade ( Zhan et al, 2020 ). As a result, contemporary genetic patterns in the species complex show muddled genetic signals ( Lee et al, 2021 ). From this, it can be inferred that the past and ongoing trade may lead to the reduction in local diversity within the B. gargarizans complex.…”