Potential mammals to investigate historical connections between Amazonian and Atlantic forests
28th January 2021 | Duration of reading: 8 min
By Arielli Fabrício Machado
Amazonian and Atlantic forests are currently separated by a wide area of dry and seasonally dry environments known as the dry diagonal. However, inside the dry diagonal there is a mosaic of forests (for example mountain forests and riparian forests). These forests are considered fragments of historical bridges that once connected the Amazonian and Atlantic forests.
There is evidence, from fossil-, climatic-, species distribution-, and genetic data that at least three routes connected the Amazonian and Atlantic forests in the past. One of the first to describe these routes was Francis Por in 1992 in the book Sooretama (a word that means “refuge for forest animals” in Tupi-Guarani).
Tropical humid forests in South America in green highlighting Amazonia and the Atlantic Forest and their past connections through 1) the Northeastern route, 2) the Central route and 3) the Southwestern route. Modified from Machado et al. 2020.
Currently, according to a review published by Ledo & Colli (2017), we know that at least 50 animal species reveal these connections. However, the current data availability, including geographic distribution data and genetic data for several species from different taxonomic groups, would certainly allow us to reevaluate the past use of these connections based on a much larger set of species.
Assessing the connections between Amazonia and the Atlantic Forest will give us insights about the past changes in forest cover and the processes behind the current complexity of these forests. Such insights can be useful in forecasts about future changes in forest cover and may thus provide an important tool for forest biodiversity conservation and maintenance.
To assist future studies on historical connections between Amazonian and Atlantic forests, we conducted a study that compiled data on potential mammal species for investigating the historical connections between Amazonia and the Atlantic Forest and which may serve as a basis for future studies. We compiled geographic distribution data from the International Union for Conservation of Nature (IUCN) Red List of Threatened Species database, which provides various data for species worldwide. We also compiled all the genetic data that was available for these species in the Genbankdatabase, one of the largest public databases of genetic sequences.
Our study revealed over one hundred mammal species with high availability of genetic data (about 176 thousand sequences). This highlights their potential for phylogeographic studies to investigate the past connections between Amazonia and the Atlantic Forest. In our publication we provide a full list of the compiled data and an access link to the database containing the filtered genetic information for each species. Hence, we hope to facilitate and promote future studies on these connections based on mammal species.
Among the different mammalian groups, armadillos and bats showed the greatest availability of data as they are of public health interest. However, also the other mammalian groups showed a high availability of genetic data and consequently a high potential for further studies focusing on the past connections between Amazonia and the Atlantic Forest. This result reveals the extreme importance of making scientific data available for the development of new studies that go beyond the focus areas of the projects that generated the data.
Availability of genetic data for groups of mammals in the Amazon and the Atlantic Forest. Reprinted from Machado et al. 2020.
To test for the past existence and use of the connection routes that previous studies had proposed, we evaluated the species distribution patterns and found a different pattern in past use compared to the previous studies (we will detail our results in an upcoming science communication here on the website of Conexões Amazônicas). This result showcases the potential of mammals for investigating and bringing new knowledge about the past connections between Amazonia and the Atlantic Forest.
Some mammal species with high availability of genetic data and a potential for investigating the past connections between Amazonia and the Atlantic Forest, including endangered species. A) Pecari tajacu, catetu; B) Bradypus variegatus, sloth; C) Alouatta caraya, black-and-gold howler monkey; D) Panthera onca, jaguar; E) Leopardus tigrinus, oncilla; F) Tapirus terrestres, tapir; G) Tamandua tetradactyla, anteater. Authorship of images: A) Gabriel P. Ibáñez, B) Atlas of Living Australia, C) Juan C. Munoz, D) Erica W., E) Escola Educação, F) Charles J. Sharp, G) Sinara Conessa.
We emphasize that just like mammals, several other groups of animal and plant species have the potential to bring new information about the historic connections and past changes in forest cover through already available data. Crucially, our study can thus serve as a basis for studies that aim to understand both past and future environmental change and their influence on biodiversity.
Science is done collaboratively
This research was part of Arielli F. Machado’s Ph.D. thesis in Ecology at UFRGS. The work was completed under the guidance of Professor Leandro Duarte, and was done in collaboration with Dr. Maria João R. Pereira from UFRGS Cleuton L. Miranda from the PPG in Zoology at Museu Paraense Emílio Goeldi at Universidade Federal do Pará (UFPA), Dr Camila D. Ritter from the University of Duisburg-Essen inGermany and PhD candidate Yennie K. Bredin at the Norwegian University of Life Sciences inNorway. This research had the financial support of the Brazilian government through CNPq.
Want to know more? Access the links below!
Laboratório de Evolução Sistemática e Ecologia de Aves e Mamíferos (BiMa-Lab)
Batalha-Filho, H., Fjeldså, J., Fabre, P. H., Miyaki, C. Y. (2013). Connections between the Atlantic and the Amazonian forest avifaunas represent distinct historical events. Journal of Ornithology, 154(1): 41-50. (Link)
Costa, L. P. (2003). The historical bridge between the Amazonia and the Atlantic Forest of Brazil: a study of molecular phylogeography with small mammals. Journal of Biogeography, 30: 71-86. (Link)
Ledo, R. M. D. &, Colli, G. R. (2017). The historical connections between the Amazonia and the Atlantic Forest revisited. Journal of Biogeography, 44(11): 2551-2563. (Link)
Machado, A. F., Ritter, C. D., Miranda, C. L., Pereira, M. R., Duarte, L. (2020). Potential mammalian species for investigating the past connections between Amazonia and the Atlantic Forest. (Link)
Arielli Fabrício Machado is a biologist from the Federal University of Santa Maria (UFSM) and holds a master's degree in Ecology from the National Institute for Research in the Amazon (INPA) and a PhD in Ecology from the Federal University of Rio Grande do Sul (UFRGS). More information on Lattes, ResearchGate and Google Scholar.