New Kenyan volcano toad species reveals hidden evolution of African amphibians

• Toad found living on volcano is new species and genus

• The new species’ presence suggests we may need to rethink the evolution of Kenya’s amphibians

• Natural History Museum collections essential in identifying the toad as a new species

A remarkable discovery in the high forests of Mount Kenya has unveiled a new species of toad, known as the Kenyan volcano toad (Kenyaphrynoides vulcani). This finding is shedding light on the mysterious evolutionary history of amphibians in East Africa and challenging previous notions about the biogeographical history of the region.

The discovery of the new toad species has puzzled scientists due to its unique appearance and unexpected presence in Kenya. Contrary to the prevailing belief that most of Kenya's amphibian species originated after volcanic activity subsided millions of years ago, the Kenyan volcano toad may date back as far as 20 million years, making it significantly older than the volcanic formation of Mount Kenya itself. With only one male toad found thus far, researchers are eager to discover more individuals to piece together its extraordinary evolutionary story.

Dr. Simon Loader, Principal Curator in charge of Vertebrates at the Natural History Museum, expressed his amazement, saying, ‘Many of Kenya’s mountains are volcanic or geologically comparatively new, so to find an ancient lineage that has persisted for millions of years is mind-blowing. It’s a real conundrum to figure out how it got here.’

‘While we’re not certain, it seems like it might once have had a wider distribution and as the climate changed over the past 10’s of millions of years, it tracked the tropical forest as it moved, with the toad’s final destination being the top of Mount Kenya.’ 

The discovery of the Kenyan volcano toad challenges the notion of the "Kenyan Interval," a term used to describe the stark contrast in amphibian diversity between Kenya and its neighbouring countries. While Ethiopia and Tanzania have long been biodiversity hotspots for amphibians, Kenya's geological history, and the frequency of tectonic activity, has made it a challenging place for these creatures to thrive. The unique characteristics of K. vulcani suggest that the Kenyan Interval may not be as straightforward as previously believed.

When the toad was first discovered in a pitfall on Mount Kenya back in 2015, it already appeared to be very different from the species that are normally found in the region. Drs Patrick Malonza and Victor Wasonga, curators at the National Museums of Kenya, who were co-authors on the paper, were the first to realize that this is something new, ‘We were really surprised to see this animal – it didn’t look like anything we had seen before but resembled something we knew from Tanzania called Churamiti maridadi, a forest tree toad from the rainforests of the Ukaguru mountains.

‘When my colleagues in Kenya sent me this picture of an unidentified toad they thought it was unusual and I instantly agreed it was really interesting.’

To confirm if this was a new species the toad needed to be compared to other species that live in the region. London’s Natural History Museum was chosen as it has a world-leading collection of toads from East Africa, which have been built up by successive curators over the years. The toad was loaned to Dr Loader so that characteristics such as its shape, colour and DNA could be compared to the other specimens. They revealed that not only was the toad a new species, but in fact an even more distinct branch of the tree of life known as a genus.

The new toad's distinct features include a smaller size, a more frog-like body, and distinctive green and brown markings. Its genetic and morphological differences from other known toad species have led to its recognition at the genus level. Despite being formally described as a new species, much remains unknown about the toad. Clues from its physical characteristics, such as enlarged fingertips suggest it may be a climber. Its thumbs also have sharp points known as nuptial spines which are found in many male frogs and toads, as they help the male grab onto a female and stimulate them into breeding.

Dr Hendrik Müller, curator at the Natural Sciences Collections and expert on developmental biology in amphibians at the Martin-Luther-University Halle-Wittenberg who is also a co-author on the paper said, ‘These forest toads found in mountains in East Africa are unusual and don’t look like a typical toad. More interestingly, several are known have an unusual breeding strategy called ovo-vivipary. In ovo-viviparity the eggs hatch inside the female. This means that the young emerge from the mother as small toads, rather than as tadpoles.’

The discovery of the Kenyan volcano toad has raised questions about the possible existence of additional undiscovered amphibian lineages in East Africa, emphasizing the need for further research and exploration in the region.

‘We don’t know everything about the main groups of amphibians, and probably only understand a small proportion of their true diversity,’ says Dr Christoph Liedtke, postdoctoral researcher at the Estación Biológica de Doñana, in Seville, Spain, and first author on the paper, ‘While this new genus doesn’t change our whole view of the Kenyan Interval, it suggests that the reality is much more complex than has been suggested. We can’t presume on geology alone that other amphibian lineages don’t exist, suggesting there could be more forest toads to find in East Africa.’

As researchers continue the quest to uncover the secrets of the Kenyan volcano toad, the single known specimen will be returned to the National Museums of Kenya for further study. This unique find underscores the richness of East Africa's biodiversity and the ever-evolving understanding of the region's natural history.

The paper, A new genus and species of toad from Mount Kenya illuminates East African montane biogeography, is published in the Zoological Journal of the Linnean Society. Access the paper here. 

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