Bolivian Beaked Toad Belongs to New Species, 20-Year DNA Sequence Corrects Decades of Misidentification

After being mistakenly labeled for decades, the Bolivian beaked toad with red warts has been discovered as a new species thanks to 20 years of DNA sequencing.

Misidentified Bolivian Beaked Toad

A South American toad with red warts and green eyes was wrongly classified for years. Recently, researchers analyzed old frozen samples, unveiling a new, endangered species in Bolivia. Jörn Köhler, the study's lead author, emphasized two decades of museum specimen review and DNA sequencing to identify the populations. Köhler highlighted the astonishing long-term misidentification of the species.

20 years of DNA Sequencing

The researchers found that previous classifications placed the populations under different nominal taxa: Rhinella fissipes and R. leptoscelis. Through thorough morphological comparisons and a phylogenetic analysis using the mitochondrial 16S rRNA gene, they identified these populations as a distinct lineage within the Rhinella veraguensis species group.

They are closely related to R. rumbolli in northern Argentina but distantly related to R. leptoscelis, sharing several morphological traits with the latter. Specimens were euthanized with chlorobutanol solution, and tissue samples were stored in 99% ethanol. Fixed specimens were stored in 70% ethanol and deposited at the Zoologisches Forschungsmuseum Alexander Koenig Bonn (ZFMK), Germany, after sexing through gonad examination.

New Species: Rhinella Kuka

The newly discovered species, named Rhinella kuka, belongs to the Rhinella genus of beaked toads found in the Americas' tropical regions. Its name derives from the indigenous term for the coca plant, found near where specimens were located. Some female toads were found carrying eggs. These reddish toads are approximately 2.5 inches long and are believed to inhabit the Bolivian Yungas, a tropical forest in the country's center.

Unfortunately, this habitat is shrinking, as Bolivia's forests have been steadily decreasing over decades. Bolivia has the 7th largest tropical rainforest area globally, but deforestation rates have risen in recent decades, losing about 430,000 hectares of forest annually from 2000 to 2010, primarily due to agricultural expansion.

Land use changes in Bolivia often follow patterns similar to those in land-abundant tropical regions, resembling variations of slash-and-burn agriculture with four main phases: land clearing and large-scale forest burning, agro-pastoral land use, soil depletion or weed infestation, land abandonment, and secondary vegetation regrowth. Some areas undergo long fallow periods before returning to agriculture once soil recovers, while others are entirely abandoned.

In locations with high land values, near urban areas, intensification can bypass phase 3 by using fertilizers, pesticides, and innovative farming methods, enabling continuous agricultural use. In certain cases, forests are cleared primarily for property rights, as observed in Brazil, or accidentally due to fires, more common in Bolivia.

Industrial-scale activities, like soybean cultivation, make regeneration difficult, even if the land is eventually abandoned. The new vegetation may have a different species composition than the original forest. Partial forest degradation occurs through selective logging or accidental fires. Researchers encounter forests in various states, each with distinct carbon storage levels. This study is the first to consider this diversity in land use outcomes in carbon accounting.

Consequently, Rhinella kuka's habitat is becoming smaller along with Bolivia's forests.

As a result, scientists suggested that the toad be classified as "vulnerable" by the International Union for the Conservation of Nature (IUCN).

According to Köhler, the discovery of the species is all the more significant given the loss of habitat in Bolivia.