ECR Feature: Felipe Camurugi on gladiator treefrog biogeograhy

Felip Camurugi is a postdoc at Universidade Federal do Mato Grosso do Sul. He is a biogeographer with an interest in anurans and their diversity. Felipe shares his recent work on gladiator treefrogs from South American and his tests for the presence (or absence) of cryptic lineages in this species.

Felipe Camurugi in the field, collecting herps. Photo credit: Sandro Paulino.

Personal links. ResearchGate

Institute. Universidade Federal do Mato Grosso do Sul

Academic life stage. Postdoc

Current study system. My main research focus is to explore the roles of landscape heterogeneity on the genetic divergence of anurans from open and dry environments of South America. The gladiator treefrog, Boana raniceps, is distributed at a continental scale, occurring in lowlands of the South American open and dry formations. Therefore, it is an interesting organism to study how past and current landscape changes can affect species’ distributions and gene flow across these environments. In addition, Boana raniceps is a generalist species associated with lentic water bodies of almost all major river basins, which enables the testing of several hypotheses on diversification in the Neotropics.

Recent paper in JBI. Camurugi, F., Gehara, M., Fonseca, E.M., Zamudio, K.R., Haddad, C.F., Colli, G.R., Thomé, M.T.C., Prado, C.P., Napoli, M.F. and Garda, A.A., 2021. Isolation by environment and recurrent gene flow shaped the evolutionary history of a continentally distributed Neotropical treefrog. Journal of Biogeography. 48: 760-772

Motivation behind this paper. The seasonally dry tropical forest Caatinga, the Cerrado savanna, and the Chaco have a complex geomorphological and climatic history. Only in the past few years have we begun testing the main promoters of genetic divergence and testing new hypotheses about diversification processes for the region. Given the wide distribution of Boana raniceps, which occurs across a broad environmental gradient, we were curious as to whether this “species” actually exhibited cryptic diversification (undescribed species forming a species complex), or, conversely, was an uncommon case of an anuran species with a broad, continental-level distribution. Additionally, this species provided a good system to test classical biogeographic hypotheses of how landscape features have shaped historical and contemporary patterns of genetic variation. 

Gladiator treefrog (Boana raniceps) in northeast Brazil.

Key methodologies. The combination of phylogeographic and landscape genetics tools has increased in the past few years, providing new opportunities to disentangle the relative roles of historical and contemporary processes of landscape changes on connectivity and genetic diversity among populations, and divergence among species. Using several complementary approaches, such as population assignment tests, species distribution models, approximate Bayesian computation, and niche comparisons, we could identify the geographical break of lineages and infer the main mechanisms involved in the processes of population/species diversification.

Major results. Our study suggests that the evolutionary history of the gladiator treefrog, Boana raniceps, was mediated by climatic shifts during the Pleistocene and topographic complexity in central Brazil. We identified two lineages that occupied different environmental niches. These lineages diverged during the mid-Pleistocene (~340,000 years ago) and kept gene flow until Last Glacial Maximum (LGM: ~21,000 years ago). During the dry and cold periods, such as the LGM, areas facilitating connectivity between populations probably shrank, reducing historical gene flow. In addition, Boana raniceps lives in lowland areas, which means that areas with a very complex topography may have hindered the migration of individuals over thousands of years, and together with the contraction of open and dry biomes during LGM, have reinforced the genetic differences within this species. Areas with this profile are located, for example, in the Brazilian Central Plateau region, which coincides with the geographical division between the two lineages. However, the environmental factors that restricted gene flow over years were clearly semipermeable, as the overall genetic divergence among populations was shallow.

Landscapes of open and dry environments of South America: Caatinga.

Challenges and unexpected outcomes. To evaluate divergence among populations of Boana raniceps, we of course needed to obtain specimens from across most of the South American continent! This involved collaborations across many institutes to obtain samples covering most of the species’ distribution. In the end, we obtained a collection of approximately 300 individuals at 115 localities encompassing four countries. Anurans typically have high phylogeographic structure due to their life history strategies, such as a tendency towards philopatry and expected low dispersal ability. Consequently, species of frogs widely distributed are frequently expected to potentially show high levels of cryptic diversity. We were surprised to find that in South American, B. raniceps is a single species that is widely distributed across the continent. Despite evidence of unique, spatially structured lineages, the amount of divergence was weak and shallow. Therefore, this pattern of intense and recurrent gene flow in a highly complex landscape was unexpected.  

Landscapes of open and dry environments of South America: Chaco.

Next steps of this research. The acoustic communication in anurans is an important component in the evolution of these organisms. Thus, the next step in this research is to investigate whether does trait divergence correlates with genetic divergence and whether sexual selection can have reinforced the geographic structure in Boana raniceps. Testing whether B. raniceps females prefer calls from males of their own lineage, or if they can mate indiscriminately, can give us a clue if behavioral isolation is a possible driver of genetic differentiation, in addition to landscape features.

If you could study any organism on Earth, what would it be? I would continue to study amphibians! I am very curious about salamanders. In South America, they are relatively less diverse but still little studied. Since I saw my first Bolitoglossa salamander in the Brazilian Amazon, I’ve wondered about the ecological and historical factors that have shaped the evolutionary history of the genus in the continent. However, my curiosity about salamanders is not regionalized and it would be really cool to study them in any part of the globe.

Water bodies where Boana raniceps can typically be found.

Anything else to add? This research is part of my thesis on the biogeography and evolution of acoustic signals of Neotropical anurans, particularly the gladiator frogs of the Boana albopunctata group. Besides biogeography of amphibians at different scales (from taxa, lineages, and genealogies, for example), the frog calling behavior and its consequences on the evolutionary histories of species is a thrilling theme for me, and having water up to my waist whilst recording and collecting frogs always makes for a great time in the field. Currently, I am combining my interests in the natural history of amphibians with genetic data to explore the roles of landscape features and biotic interactions as drivers of genetic divergence at a community level.

Published by jbiogeography

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