Guibemantis rianasoa.Credit: Hugh Gabriel
Seven new frog species discovered in Madagascar over the past year mark the latest additions to a growing inventory of frogs and other amphibian species that have evolved over the past 66 million years in relative isolation on the world’s fourth largest island, confirming its role as a major hotspot for amphibian biodiversity.
Scientists have described three greenish-brown Guibemantis and four mottled-brown Gephyromantis moseri frog species in papers published in Zootaxa and Spixiana. The researchers used genetic studies and a comparison of specific calls to confirm the new species.
Although the frogs may not be Madagascar’s most colourful, eye-catching or even smallest, the identification points to the importance of the island in the study of amphibians.
“Madagascar is a real natural laboratory to understand evolution and biogeography,” says Miguel Vences of the Division of Evolutionary Biology at Braunschweig University of Technology, Germany, the lead author of the Spixiana paper.
The State of the World’s Amphibians: The Second Global Amphibian Assessment (GAA2), released in 2023, lists more than 400 amphibian species for Madagascar alone. The report, however, points to the Afrotropical area receiving considerably less research effort than other areas in the world, although it is “a treasure trove of amphibians.” The report indicates that most new species emerged from the forests of West and Central Africa and Madagascar, with more than 175 species described in the island since 2006.
Gephyromantis fuscus.Credit: Miguel Vences
Vences attributes the additions to Madagascar’s herpetofauna count over the past two decades to increased field exploration, especially to remote areas, and consistent and well-organized large-scale application of modern methods such as DNA barcoding and bioacoustic analysis.
“There is also the personal commitment of a series of Malagasy, European, and American experts who really devote a lot of effort and time to the exploration of this unique ‘microcontinent’,” he adds.
In terms of total diversity of amphibians, Madagascar is number 12 in the world, but 49% of amphibians in the island are threatened. It also ranks sixth in the GAA2 report’s list of threatened species hotspots. This threat means it is essential for researchers to devote efforts to better identifying and understanding the amphibian population in the area.
A co-author on both papers, herpetologist, Andolalao Rakotoarison of the University of Antananarivo at Soavinandriana, Itasy, and the School for International Training in Madagascar says various groups from different countries are involved in frog research. While each has their own specific focus and objectives, there is strong collaboration between groups, often informally, and sharing of data, resources, and expertise.
Guibemantis are frogs that live in water puddles collected in the leaf of the spiky pandan screwpine. Hugh Gabriel, a science educator from the USA, noticed the newly identified one during a visit in 2022 to the humid rainforests around the village of Andasibe, a known amphibian hotspot. He was busy with a student assignment on three other Guibemantis species already known in the area. These often live side by side on the same tree, along with spiders, crabs, snakes and even ants.
“I photographed and measured two frogs that I afterwards could not identify using my guidebook,” Gabriel recalls.
His curiosity led him to Vences who has helped describe many more Malagasy frog species over the past two decades. Vences and other researchers collaborating with Gabriel on the subsequent Zootaxa paper described the finds as unexpected for a well-surveyed forest such as Andasibe.
Experts anticipate that there are more of these ‘unexpected’ findings, highlighting the need for more research efforts in that area in specific, as well as in the field of biodiversity in general.
“An accurate and complete species inventory remains crucial for understanding ecological and evolutionary dynamics and for effective conservation management. The ethical responsibility to document and conserve Earth's biodiversity is as pertinent as ever, especially given the ongoing threats posed by habitat destruction, climate change, and other anthropogenic pressures,” Rakotoarison adds
