Amphibians
Caucasian toad status is under review - what the new genomic study shows
A genomic study in Molecular Phylogenetics and Evolution questions the separate-species status of the Caucasian toad, but the taxonomic change is not a settled decision yet.
The Caucasian toad is treated as a separate species in Georgia, but a new 2026 genomic study reopens that status. According to the authors, the Caucasian lineage appears in the nuclear genome as a relatively shallow lineage within Bufo bufo and shows broad genetic mixing with the Balkan lineage in Anatolia. That is important evidence, but it does not mean Bufo verrucosissimus has already been officially 'cancelled'.
Status under review, not closed
Is the Caucasian toad really an independent species? The new study makes the question more complicated than a yes-or-no answer. Genomic data suggest that the Caucasian population may not be as deeply separated from Bufo bufo as expected under a clear separate-species interpretation.
This is not a story that the Caucasian toad no longer exists. Taxonomic changes do not happen in one day. A paper can be important while accepted names, checklists, and international databases change only after broader scientific uptake.
What the scientists studied
The paper was published on 10 September 2026 in Molecular Phylogenetics and Evolution. It studies the Western Palearctic common toads, the Bufo bufo complex, using genome-wide ddRAD-seq nuclear data together with a broad mitochondrial dataset.
The analysis clearly recovered three recognized species: Bufo eichwaldi, Bufo spinosus, and Bufo bufo. Within Bufo bufo, the authors discuss Apennine, Balkan, Caucasian, and northern European lineages.
Who is Bufo verrucosissimus
The Caucasian toad, Bufo verrucosissimus, is a forest amphibian directly relevant to Georgia's fauna. On Reptiles.ge it is currently shown as a separate species, while its profile already notes that the 2026 Georgian checklist leaves species rank as a candidate issue relative to Bufo bufo.
Amphibian Species of the World's current record still displays it as a separate species entry and gives a distribution including the western Caucasus, Georgia, northern Azerbaijan, northeastern Turkey, and related areas. The same page's historical comments show that this taxon's status has long been debated.
What the genomic result shows
The key point is that nuclear DNA and mitochondrial DNA do not always tell the same story. In this study, the nuclear ddRAD-seq data place the Caucasian lineage as a relatively shallow lineage within Bufo bufo, while mitochondrial signals can preserve older geographic patterns.
The authors also report broad intergradation between Caucasian and Balkan lineages in Anatolia. Gene flow does not automatically make two lineages one species, but in this case the authors combine several lines of evidence and treat the Caucasian lineage's position as an argument against separate-species status.
Why the name has not simply disappeared
A proposed taxonomic interpretation in a paper and a changed accepted name in databases are not the same thing. On 16 September 2026, Amphibian Species of the World added comments on the Dufresnes et al. paper to Bufo, Bufo bufo, Bufo verrucosissimus, Bufo spinosus, and Bufo eichwaldi.
At the time this article was prepared, the Amphibian Species of the World page for Bufo verrucosissimus still reads as a separate species entry. The precise conclusion is therefore not 'removed', but 'status needs review'.
What it means for Georgia
For Georgia, this is first a taxonomy and database question. If the new interpretation becomes widely accepted, names in Georgian amphibian lists, atlases, and conservation datasets may need updating later.
It does not mean that Georgia's fauna has already 'lost' a species today. Reptiles.ge should not change the species page on the basis of one paper alone; the site should follow taxonomic developments through international sources and regional checklists.
Sources
Recurrent hybridization shapes the diversification of Western Palearctic common toads (Bufo bufo complex). Christophe Dufresnes et al. Molecular Phylogenetics and Evolution, 226:108738, published online 10 September 2026. DOI: 10.1016/j.ympev.2026.108738.
ScienceDirect record, PubMed record, and Amphibian Species of the World 2026 updates.
