A taxonomic integrative approach of the anuran species from a Cerrado-Amazonian transitional area in western Tocantins state, Brazil.

Due to their complexity environments, ecotonal areas harbor high levels of biodiversity. The Cerrado is geographically situated among other Brazilian biomes and exhibits extensive transitional areas with neighboring biomes. The state of Tocantins, in northern Brazil, has a vast transitional area between the Cerrado and Amazonia in the North and West. Despite the remarkable richness revealed in recent studies, the anuran fauna of Tocantins is likely underestimated, as several municipalities have knowledge gaps, particularly those located in these Cerrado-Amazonia transitional areas. Here, we improve the knowledge of amphibians' diversity in a Cerrado-Amazonia transitional area in western Tocantins state using integrative taxonomy. We conducted four field expeditions in the Caseara municipality, totaling 50 days of fieldwork. We performed diurnal and nocturnal active surveys and installed pitfall traps along an environmental gradient, ranging from typical Cerrado habitats to typical Amazon habitats. We combined morphology, bioacoustic, and mtDNA to improve the identification of the collected specimens. In total, we collected 738 vouchers assigned to 42 species belonging to seven families. We also present morphometric data for 38 of the recorded species (n = 609), acoustic data for 19 species, and 21 new 16S mtDNA sequences for seven species. These new data were essential to identify 38 of the 42 recorded species at the species level, including interesting new records for species like Allobates crombiei and Scinax similis. Four recorded species remained with an undefined status: Boana sp. (gr. semilineata), Adenomera sp. (aff. hylaedactyla), Physalaemus sp. (gr. cuvieri), and Proceratophrys sp. (cf. ararype). We encourage the use of similar approaches in species inventories to ensure taxonomic accuracy and to provide reliable data for conservation policies.