A group supported by FAPESP and led by University of São Paulo (USP) researchers in Brazil has described a new genus of frogs, Dryadobates , also known as rocket frogs, which was previously considered a single species. The study was published in the Bulletin of the American Museum of Natural History.
The researchers used techniques that allow the analysis of degraded DNA obtained from specimens preserved in alcohol or formalin and deposited in natural history collections. Adapted from techniques initially developed for ancient DNA studies, such as those of extinct hominids, historical DNA analysis (hDNA) techniques are having a significant impact on species discovery and the detection of recent extinctions (read more at agencia.fapesp.br/55064 ).
By comparing sections of the genome of museum animals with those of animals living in different parts of the Atlantic Forest, the authors concluded that the widely distributed species considered a single species is actually a much larger group of at least 12, possibly 16, species.
The preserved frogs in museums actually belong to four species, three of which are likely extinct. The remaining eight species inhabit various regions of the Atlantic Forest in the states of Espírito Santo and Bahia.
"It's a study that reveals both hidden diversity and hidden extinctions. It's wonderful that we can learn more about species at this level of detail, but very sad to know that others have already been lost and we didn't even know about them," says Taran Grant , a professor at the Institute of Biosciences (IB-USP) who coordinated the study.
The work is part of the second phase of the project "A Multidisciplinary Approach to the Study of Amphibian Diversification" , which is supported by FAPESP. This funding enabled the researcher to establish the Historical DNA (hDNA) Laboratory at USP.
Measuring less than two centimeters in length, Allobates olfersioides was first described a century ago by Adolpho Lutz (1855-1940), a public health physician who also conducted natural history studies based on specimens from the coast of Rio de Janeiro.
In 1967, zoologist Werner Bokermann (1929-1995) described three new species that were very similar but lived in different locations. These species were Allobates alagoanus in the state of Alagoas, Allobates capixaba in Espírito Santo, and Allobates carioca in another location in Rio de Janeiro.
However, in 2007, as part of a project supported by FAPESP , Vanessa Verdade , who was a master's student at the time and is now a professor at the Federal University of ABC (UFABC), and Professor Miguel Trefaut Rodrigues from IB-USP analyzed 880 specimens from 29 locations in the Atlantic Forest. They concluded that there were not enough morphological differences to classify the species as distinct. They were all then grouped into a single species, Allobates olfersioides, which was first described by Lutz.
However, there was one problem. It was no longer possible to find specimens in the locations where he and Bokermann had initially collected the animals.
The recently published study, also signed by Verdade and Rodrigues, points out that these were not populations of the same species, as was previously thought, but rather, different species that are likely extinct. For example, no individuals of A. olfersioides have been found since 1981. This species was probably endemic to the Angra dos Reis region in Rio de Janeiro.
The differences between the Allobates of the Amazon and the frogs of the Atlantic Forest justified the creation of a new genus, Dryadobates, for the latter. The three species originally described by Bokermann were reclassified under the new genus. Two of the eight new species were named in honor of the two pioneers who studied the group: Dryadobates lutzi and Dryadobates bokermanni. Both species are found in southern Bahia.
The group is still searching for more specimens and evidence that will allow for robust differentiation of the other six species from a genetic, bioacoustics (animal sound), and morphological perspective.
Conservation
"The fact that there are several species rather than one widely distributed species changes everything. Since the Atlantic Forest is highly fragmented and very susceptible to habitat loss, each species may be facing different problems, which require specific actions for each one," Grant warns.
Due to its presumed wide distribution, Allobates olfersioides is still classified as "least concern" on the Red List of Endangered Species of the International Union for Conservation of Nature (IUCN), the leading reference for the conservation status of species worldwide.
However, in its latest version from 2018, the Brazilian list of endangered species classifies the species as "vulnerable" while recognizing A. alagoanus and A. capixaba as valid, albeit with "data deficient" status. There is no mention of A. carioca, and classifications vary across state lists.
The recently published study points out that D. capixaba, D. carioca, and D. olfersioides appear to be extinct. In contrast, D. alagoanus, D. bokermanni, and D. lutzi are abundant in multiple locations with no evidence of decline. According to the IUCN criteria, this classification places the latter three species as "least concern" for extinction. These species thrive not only in forests but also in cabrucas, which are woods used to shade cocoa plantations.
"However, the fact that 25% of the known species of this genus have become extinct in the last 50 years is alarming and suggests that even those species that could be classified as of least concern should be carefully monitored," Grant cautions.
Of the six unclassified species, four are locally abundant but are only known from one location each. The other two species are known from only a few specimens, also from a single location each.
"Fieldwork is being done to collect and classify these species, but we need specimens of different sexes and stages [adults, juveniles, tadpoles], as well as to search in new locations to ensure a robust classification," says the researcher.
Grant also says that it is necessary to determine whether the populations that appear to be extinct in Santa Teresa (Espírito Santo) and Tijuca National Park (Rio de Janeiro) are of species that have already been described or of other species. If the latter is true, six species would be considered extinct, accounting for 40% of the Dryadobates genus.
There is hope because large areas of the Atlantic Forest in Rio de Janeiro, Espírito Santo, and Bahia have not yet been sampled by the researchers. This opens up the possibility that new species of the genus may still be discovered.
The work was also supported by FAPESP as part of a project under the FAPESP Research Program on the Characterization, Conservation, Restoration, and Sustainable Use of Biodiversity ( BIOTA-FAPESP ).
About São Paulo Research Foundation (FAPESP)
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