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New toads named from a Sumatran biodiversity trove that’s under threat

The Gayo Lues puppet toad (S. gayoluesensis), Image by Eric N. Smith.

  • Researchers have recently described three new species of toads belonging to the Sigalegalephrynus genus of puppet toads living in the highlands of Indonesia’s Sumatra Island.
  • The genus was first proposed in 2017 with the description of two species. Researchers believe there may be even more puppet toads left to discover.
  • The discovery highlights the vast diversity of Sumatra’s herpetofauna, but also the immense threats the island’s wildlife faces, primarily from loss of habitat to deforestation and agriculture.
  • The researchers say all of the newly described species should be listed as endangered on the IUCN Red List.

In 2017, a group of researchers working in Indonesia announced they had identified a new genus of tree-dwelling toads living in forests and caves on the mountaintops of Indonesia’s Sumatra Island.

Their paper at the time identified two species belonging to what they described as the genus Sigalegalephrynus, or puppet toads, named after the Sigale-gale puppets used in local funerary traditions. Now, in a new paper published in October 2019, the team has described three additional species belonging to the genus, highlighting the stunning and largely underexplored diversity of reptiles and amphibians in Sumatra.

“Sumatra is one of the islands of the world that harbor highest level of biodiversity and we are convinced that we barely scratched the surface of it,” said lead author Goutam Sarker, a herpetologist at the University of Texas at Arlington, in an email to Mongabay. “Very confidently, we can say there are many more new taxa awaiting discovery.”

The research team conducted surveys between 2013 and 2016, funded by a grant from the U.S. National Science Foundation. The team, which includes scientists from research institutes in Indonesia, the United States and Germany, spent 178 days in the field collecting samples. Conditions were often grueling; Sarker recalls falling backward off a “3.5-4 meter high” cliff, about 12 feet, during a nighttime survey in Aceh province. A backpack full of air-filled specimen bags cushioned his fall. “Otherwise, I would be dead,” Sarker recalls.

But the work paid off.

The five species identified as belonging to the genus Sigalegalephrynus were each found in a single habitat in Indonesia’s Sumatra Island. Image courtesy of Goutam Sarker.

The team’s first batch of analyses, based on samples collected in 2013 and 2014, led to the proposal of the new genus and the description of two species in 2017: the Mandailing puppet toad (Sigalegalephrynus mandailinguensis) and Minangkabau puppet toad (S. minangkabauensi).

Analysis of a second batch of samples, collected in 2015, resulted in the description of three new species: the Burning Mountain puppet toad (S. burnitelongensis), Gayo Lues puppet toad (S. gayoluesensis), and Harvey’s puppet toad (S. harveyi).

The newly described toads are small (adults measure less than 40 millimeters, or 1.6 inches), have distinctly shaped finger pads and foot webbing, have unique mating calls, and live in trees and caves, setting them apart from other toad genera found in Sumatra. The known species within the genus exhibit clear genetic lineages, with the newly described Gayo Lues and Burning Mountain puppet toads forming a northern branch of the genus, and Harvey’s puppet toad joining the two previously described species in a southern branch.

One of the distinguishing features of the proposed genus Sigalegalephrynus is its distinctive metacarpal tubercle, highlighted here. Image courtesy of Goutam Sarker.

And the researchers believe there are more species yet to be identified.

 “I am very positive that new species of this genus will be discovered by other research groups soon,” Sarker says. In fact, he notes that based on a recent analysis, his team believes they may already have a sample of yet another species in their own collection.

The newly-described Harvey’s puppet toad (S. harveyi). Its only known habitat is the montane cloudforest on the southeastern slopes of Mount Dempo in South Sumatra. Image by Eric N. Smith.

Diversity under threat

Sarker says the researchers were “astonished” at the micro-endemic nature of the species they observed, meaning that each species appears to be restricted to a tiny, specific location.

Historical geological events likely played a major role. Many studies have shown that when sea levels were higher, Sumatra’s lowland forests were underwater, transforming upland areas into isolated islands, Sarker says. “Also, maybe, since these are highland species they did not came down and interbreed when sea level dropped.”

The extremely small range of each species means that they are highly vulnerable to any changes in their home environment. And today, that vulnerability is increasing as pressure rises on the ecosystem due to deforestation, agriculture — notably oil palm and coffee cultivation — and expanding human settlement.

The Burning Mountain puppet toad (S. burnitelongensis), has been found only in forest patches near small streams and surrounded by coffee plantations at Mount Burni Telong, near the village of Rambune in Aceh province. Image by Eric N. Smith.

In addition to describing the three new species, the team’s October paper also calls for all five member of the Sigalegalephrynus genus to be listed as endangered species by the IUCN. “I have no reservation to say that all these toads should be placed, at least,into the Endangered category if not Critically Endangered of the IUCN Red List,” Sarker says.

“Sadly, almost 80-90% of Sumatra’s rainforests have been replaced with palm oil plantations,” says Michael Harvey, a herpetologist at Broward College in the U.S, and one of the recipients of the grant that funded the Sumatra survey work (and the namesake of Harvey’s puppet toad). “Discovery of these toads suggests that many more new reptiles and amphibians occur on Sumatra than previously thought. With current rates of deforestation, many of these animals will likely go extinct before they are discovered.”

Banner image: The Gayo Lues puppet toad (S. gayoluesensis),  only known to live above Kenyaran Pantan Cuaca village in Aceh province’s Gayo Lues regency, by Eric N. Smith.

Citation:

Sarker, G. C., Wostl, E., Thammachoti, P., Sidik, I., Hamidy, A., Kurniawan, N., & Smith, E. N. (2019). New species, diversity, systematics, and conservation assessment of the puppet toads of Sumatra (Anura: Bufonidae: Sigalegalephrynus). Zootaxa4679(2), 365-391. doi:10.11646/zootaxa.4679.2.9

This article was updated to correct the height of the cliff researcher Goutam Sarker fell from.

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