The DNA of historic and current population reveals at least 12 species of rocket frogs, three of which are already extinguished

A group led by researchers from the University of São Paulo (USP) in Brazil has described a new kind of frogs, the Dryadobates, also known as rocket frogs, which was previously considered one species. The study was published in the Bulletin of the American Museum of Natural History.

The researchers used techniques that allow degraded DNA analysis obtained from samples preserved in alcohol or formalus and deposited in natural history collections. Adapted from the techniques initially developed for old DNA studies, such as those of extinguished hominids, the historical techniques of DNA analysis (HDNA) have a significant impact on the discovery of species and the detection of recent extinctions.

By comparing the sections of the genome of museum animals with those of animals living in different parts of the Atlantic forest, the authors concluded that the largely distributed species considered as one species are in fact a much larger group of at least 12 species, perhaps 16 years.

The frogs kept in museums actually belong to four species, three of which are probably extinguished. The remaining eight species live in various regions of the Atlantic forest in the states of Espírito Santo and Bahia.

“It is a study that reveals both hidden diversity and hidden extinctions. It is wonderful that we can know more about the species at this level of detail, but very sad to know that others have already been lost and that we do not even know them,” explains Taran Grant, professor at the Institute of Biosciences (IB-USP) which coordinated the study.

The work is part of the second phase of the project “A multidisciplinary approach to the study of the diversification of amphibians”.

Measuring less than two centimeters, Allobats Olfersioides was described for the first time a century ago by Adolpho Lutz (1855-1940), a public health doctor who also conducted natural history studies based on specimens of the Côte de Rio de Janeiro.

In 1967, the zoologist Werner Bokermann (1929-1995) described three new species which were very similar but lived in different places. These species AlloBatent Alagoanus in the state of Alagoas, Allobate Capixaba in Espírito Santo and Allobe Carioca in another place in Rio de Janeiro.

However, in 2007, as part of a project, Vanessa Verdade, who was a master’s degree at the time and was now a professor at the Federal University of ABC (UFABC), and Professor Miguel Trefaut Rodrigues of IB-USP analyzed 880 specimens of 29 places in the Atlantic forest. They concluded that there were not enough morphological differences to classify the species as distinct. They were then grouped into a single species, Allobes the Olfersioides, which were first described by Lutz.

However, there was a problem. It was no longer possible to find samples in the places where he and Bokermann had originally collected animals.

The recently published study, also signed by Verdade and Rodrigues, stresses that they are not populations of the same species, as it thought before, but rather, different species that are probably extinguished. For example, no individual from A. Olfersioides has not been found since 1981. This species was probably endemic to the region of Angra Dos Reis 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 genre, Dryadobates, for the latter. The three species originally described by Bokermann were reclassified under the new genre. Two of the eight new species have been appointed in honor of the two pioneers who studied the group: Dryadobates Lutzi and Dryadobates Bokermanni. The two species are found in southern Bahia.

The group is looking for more samples and evidence that will allow a robust differentiation of the other six species of a genetic, bioacoustic (its animal) and morphological perspective.

Conservation

“The fact that there are several species rather than a largely distributed species changes everything. Since the Atlantic forest is very fragmented and very sensitive to the loss of habitat, each species can be confronted with different problems, which require specific actions for each,” warns Grant.

Due to its alleged large distribution, Olfersioides’ allobats are still classified as “less worrying” on the red list of endangered species of the International Union for Nature Conservation (IUCN), the main reference for the status of conservation of species in the world.

However, in its latest version of 2018, the Brazilian list of endangered species classifies species as “vulnerable” while recognizing A. Alagoanus and A. Capixaba as valid, although with the “data deficient” status. There is no mention of a. Carioca and classifications vary to the other from state lists.

The recently published study underlines that D. Capixaba, D. Carioca and D. Olfersioides seem to be extinguished. On the other hand, D. Alagoanus, D. Bokermanni and D. Lutzi are abundant in several places without a sign of decline. According to IUCN’s criteria, this classification places the last three species as “the least worrying” for extinction. These species thrive not only in the forests but also in the Cabrocas, which are woods used to shade cocoa plantations.

“However, the fact that 25% of known species of this genus have turned off in the past 50 years is alarming and suggests that even species that could be classified as the slightest concern should be carefully monitored,” warns Grant.

Of the six non -classified species, four are locally abundant but are only known in one place each. The other two species are known from a few samples, also from a single location each.

“The field work is 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 places to ensure a robust classification”, explains the researcher.

Grant also says that it is necessary to determine whether the populations that seem to die out in Santa Teresa (Espírito Santo) and the Tijuca National Park (Rio de Janeiro) are species that have already been described or other species. If the latter is true, six species would be considered extinguished, representing 40% of the genus Dryadobates.

There is hope because large areas of the Atlantic forest in Rio de Janeiro, Espírito Santo and Bahia have not yet been sampled by researchers. This opens up the possibility that new species of the genre can still be discovered.