- DNA testing of two new-to-science frog species has shown they share a common ancestor — a species that lived 55 million years ago in the mountains of what is today Brazil’s Amazonas state.
- The multidisciplinary study drew together biologists and geologists to map how geological changes in the mountain range shaped not just its geography but also the diversity of species in the region.
- The two endemic species were collected on two separate peaks — Neblina and Imeri — and their discovery has led to further understanding of the origins and evolution of biodiversity in the Amazon.
- Another expedition to the Tulu-Tuloi Range, located 200 kilometers (120 miles) from Imeri, is scheduled for 2025.
The frog’s loud croaking turned out to be a call to its own demise. The researchers walking along the steep muddy bank on a rainy November day in 2022 in the Imeri Range on the Brazil-Venezuela border were alerted by the unfamiliar sound. They found the frog sitting outside the opening to a tarantula’s burrow and captured it. They later named the frog Neblinaphryne imeri.
“That was the most difficult expedition I’ve ever been on in my entire life,” says Miguel Trefaut Rodrigues, a herpetologist at the University of São Paulo (USP). Rodrigues has been doing fieldwork for more than 40 years, and this time he was leading a team of 14 researchers on a 12-day camping expedition at the top of a nearly 1,900-meter (6,200-foot) peak.
Even the region’s Indigenous Yanomami don’t climb to the Imeri peak because of the treacherous route and the fact that there are no large mammals to be hunted at that altitude. Rodrigues’s team only managed to reach the spot with a Brazilian military helicopter.
This was the second time Rodrigues had led an expedition of researchers, with the help of the military, in this part of Brazil’s Amazonas state. The first was to the Neblina peak in 2017, some 80 kilometers (50 miles) from Imeri. Both mountains are located inside protected areas: Pico da Neblina National Park and the Yanomami Indigenous Territory, respectively.
The Neblina expedition also resulted in the discovery of a previously undescribed frog species, which they named Neblinaphryne mayeri after Sinclair Mayer, the military general who helped organize that expedition.
After much study, the scientists have concluded that the two frog species — the one from Neblina and the one from Imeri — are closely related, diverging from a common ancestor that last roamed this region 55 million years ago, before a series of significant geological changes.
A common ancestor
“These animals are helping us rediscover a very important part of Earth’s history and South American history that was unknown to us,” Rodrigues says.
Climatic conditions at the top of these mountains are very different than in the hot regions at lower elevations in the Amazon. This results in a host of species that have adapted to the climate, including those that seldom descend to the lower elevations of the rainforest.
DNA testing carried out on the two new frog species dated their common ancestor back to a time when the peaks of Neblina and Imeri were probably connected. In the millions of years since then, steady erosion by wind and water ate away at the mountains, creating the lower regions of the forest pierced by the isolated peaks we have today.
As a result of this geological transformation, the frogs on the two peaks evolved separately, in isolation.
“Essentially, the age of the divergence tells us how long the barrier that separates the two species has existed,” says André Sawakuchi, a geologist at USP. “Migration barriers can be large rivers, areas with different vegetation than the species in question’s habitat, or mountains, among other features. The species’ age gives us an idea of the ages of the valley and of the mountains
Learning about the future from the past
Biologists and geologists often work together to gain a better understanding of the biodiversity and landscapes of tropical rainforests. It’s a field of study called geogenomics, a term coined by geologist Paul Baker at Duke University in the U.S., who showed how hypotheses can evolve through collaboration between specialists.
Lúcia Lohmann, a researcher at USP’s Institute of Biosciences and the University of California, Berkeley, coordinates projects in the Amazon with scientists from other areas of study.
“Holistic studies combining information from different fields of knowledge like biology, geology and climatology are essential for our understanding of biodiversity’s origins and the adaptations that have occurred over millions of years,” Lohmann says. “Understanding the past and our origins is extremely important for us to be able to predict the future more accurately, to establish public policy and strategies so biodiversity can be protected.”
Lohmann took part in the Imeri expedition, which collected more than 1,200 plant samples representing around 220 species, most of them endemic to the region.
“We collected material from all the botanical families that we found, everything from bryophytes, ferns, carnivorous plants and giant bromeliads to palm trees, orchids and conifers,” Lohmann says. “A good share of the material we collected represents new records and at least a dozen are new species to science.”
Documenting the biodiversity of unknown regions at a time when a large number of species are at threat of extinct is an urgent scientific task.
“The material we collected is adding new pieces to the large puzzle describing the origin and evolution of Amazonian biodiversity,” Lohmann says. “We believe that many plant lineages emerged in the parts of the forest at higher elevations and later migrated to the lower regions. The data collected will allow us to understand the routes they took, past connections with other biomes and processes that led to the formation of the elaborate diversity of the species found throughout Latin America as a whole.”
Describing new findings
By the age of 8, Rodrigues was already familiar with the coastal Jureia range in his home state of São Paulo, where he walked frequently with a fisherman he knew near the hills. Back then, he collected butterflies, beetles and other insects. Today, he can be found in Room 102 at the USP Institute of Biosciences, surrounded by reptile and amphibian specimens that are among the nearly 200 new-to-science species that he’s helped describe.
Rodrigues’s expedition found N. imeri in 2022, but their description of it as a new-to-science frog species was published in September this year in the journal Zootaxa. Rodrigues says the scientists in the expedition also teach classes, orient students, carry out their own research, and conduct extensive analyses of each species collected.
There are many steps involved in describing a new species, including analysis of photos and the call that each animal makes in its habitat; study of its physical form under a magnifying glass; measurement of all individuals collected; determination of sex; and extraction of tissue for DNA analysis and sequencing. This latter process in the case of N. imeri was carried out in South Korea. They also scan and study the skeletal structure and joints. Only after all of these processes have been completed can the new species be described.
Some species collected during the 2017 expedition are still waiting to be described.
“We should release many studies over the next two or three years, so we can at least finish the part of describing the new species from Neblina Peak,” Rodrigues says.
“We are discovering new fauna and flora from a completely unknown part of Brazil,” he says of the work. “I mean, we are filling out an unknown branch of the tree of life that could hold extremely important information.”
Rodrigues says he already has another expedition planned for 2025, to the Tulu-Tuloi Range, about 200 km (120 mi) from Imeri, also in the state of Amazonas. The Brazilian military will also provide logistical support for this expedition.
Banner image: The frog Neblinaphryne imeri, which was discovered in 2022. Image courtesy of Taran Grant.
This story was first published here in Portuguese on Dec. 5, 2024.
Citations:
Fouquet, A., Kok, P. J., Recoder, R. S., Prates, I., Camacho, A., Marques-Souza, S., … Rodrigues, M. T. (2024). Relicts in the mist: Two new frog families, genera and species highlight the role of Pantepui as a biodiversity museum throughout the Cenozoic. Molecular Phylogenetics and Evolution, 191, 107971. doi:10.1016/j.ympev.2023.107971
Baker, P. A., Fritz, S. C., Dick, C. W., Eckert, A. J., Horton, B. K., Manzoni, S., … Battisti, D. S. (2014). The emerging field of geogenomics: Constraining geological problems with genetic data. Earth-Science Reviews, 135, 38-47. doi:10.1016/j.earscirev.2014.04.001
Fouquet, A., Moraes, L. J., Grant, T., Recoder, R., Camacho, A., Ghellere, J. M., … Rodrigues, M. T. (2024). A new species of Neblinaphryne (Anura: Brachycephaloidea: Neblinaphrynidae) from Serra do Imeri, Amazonas state, Brazil. Zootaxa, 5514(1), 73-90. doi:10.11646/zootaxa.5514.1.5
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