Rising habitat loss is one of the main drivers of the global amphibian decline. Nevertheless, knowledge of amphibian diversity needed for effective habitat protection is still highly inadequate in remote tropical regions, the greater part of the Amazonia. In this study we integrated molecular, morphological and bioacoustic evidence to evaluate the species richness of the treefrogs genus Scinax over a 1000 km transect across rainforest of the Purus-Madeira interfluve, and along the east bank of the upper Madeira river, Brazilian Amazonia. Analysis revealed that 82% of the regional species richness of Scinax is still undescribed; two nominal species, seven confirmed candidate species, two unconfirmed candidate species, and one deep conspecific lineage were detected in the study area. DNA barcoding based analysis of the 16s rRNA gene indicates possible existence of three discrete species groups within the genus Scinax, in addition to the already-known S. rostratus species Group. Quantifying and characterizing the number of undescribed Scinax taxa on a regional scale, we provide a framework for future taxonomic study in Amazonia. These findings indicate that the level to which Amazonian anura species richness has been underestimated is far greater than expected. Consequently, special attention should be paid both to taxonomic studies and protection of the still-neglected Amazonian Scinax treefrogs.

Osteocephalus vilarsi (Melin, 1941) is an Amazonian treefrog species known for over 75 years from its holotype only. Due to a lack of published data on its morphological diagnostic characters and their variations, as well as the absence of molecular, acoustic and ecological data supporting its identity, a highly dynamic taxonomic history has led this species to be confused and even synonymised with other Osteocephalus species from distinct species groups. The molecular phylogenetic relationships of O. vilarsi were investigated based on recently collected specimens from eight Northwestern Brazilian localities in the state of Amazonas, leading to its removal from the Osteocephalus taurinus species group and placement in the Osteocephalus planiceps species group. Furthermore, detailed data on morphology and colour variation are provided, as well as advertisement call and tadpole descriptions. Finally, the currently known geographic range of O. vilarsi is considerably extended, first data on the natural history of the species are provided, and the possible ecological preference of O. vilarsi for Amazonian white-sand forests is discussed.

Knowledge of genetic structure, geographic distance and environmental heterogeneity can be used to identify environmental features and natural history traits that influence dispersal and gene flow. Foraging mode is a trait that might predict dispersal capacity in snakes, because actively foragers typically have greater movement rates than ambush predators. Here, we test the hypothesis that 2 actively foraging snakes have higher levels of gene flow than 2 ambush predators. We evaluated these 4 co-distributed species of snakes in the Brazilian Amazon. Snakes were sampled along an 880 km transect from the central to the southwest of the Amazon basin, which covered a mosaic of vegetation types and seasonal differences in climate. We analyzed thousands of single nucleotide polymorphisms to compare patterns of neutral gene flow based on isolation by geographic distance (IBD) and environmental resistance (IBR). We show that IBD and IBR were only evident in ambush predators, implying lower levels of dispersal than the active foragers. Therefore, gene flow was high enough in the active foragers analyzed here to prevent any build-up of spatial genotypic structure with respect to geographic distance and environmental heterogeneity.

We used integrative taxonomy to describe a new species of Atelopus from the lowlands of Central Amazonia in the region of Manaus, Amazonas, Brazil. The new species is geographically isolated from the southernmost species of Atelopus of the Guiana Shield. Atelopus manauensis species nova (sp. nov.) is characterized by the combination of the following characteristics: male snout-vent length range (SVL = 19.1–26.4 mm; n = 11); dorsal and lateral skin smooth; ventral surface entirely white or white with cream-colored gular region; fingers and toes lacking subarticular tubercles and fringes. The advertisement call of the new species has a call duration of 689–840 ms, contains 15–26 pulses, is emitted at an average pulse rate of 25.5 pulses per second, and has a dominant frequency ranging 3088–3610 Hz. The genetic divergence between the new species and its morphologically most similar congeners (A. spumarius and A. pulcher) is greater than 4%. Atelopus manauensis sp. nov. is closely related to species of the A. hoogmoedi complex inhabiting the Guiana Shield. The new species has a small geographic distribution (approximately 4500 km²) in a landscape that is strongly threatened by the growth of Manaus, the largest city in Brazilian Amazonia. The new species is considered critically endangered and in need of urgent conservation measures.

Pristimantis is already the most speciose genus among vertebrates, yet the current number of species remains largely underestimated. A member of the P. unistrigatus species group from the Guiana Shield has been historically misidentified as P. ockendeni, a species described from southern Peru. We combined mitochondrial (16S and COI) and nuclear (RAG1) loci, external morphology, skull osteology (μ-CT scan), vocalization (advertisement and courtship calls), geographic distribution and natural history data to differentiate the Guiana Shield populations from P. ockendeni, and describe them as a new species. The new species is crepuscular and nocturnal and inhabits the understory of unflooded (terra firme) forests in Brazil, Guyana and Suriname. It is phylogenetically related to P. arda­lonychus, P. martiae and undescribed species from Brazilian Amazonia. The new species notably differs from P. ockendeni and its congeners in the P. unistrigatus species group occurring in the Guiana Shield by the combination of the following characters: absence of dentigerous processes of vomers, presence of vocal slits in males, body size (SVL 16.2–20.7 mm in males and 21.4–25.7 mm in females), advertisement call (call with 4–6 notes, call duration of 158–371 ms and dominant frequency of 3,466–4,521 Hz) and translucent groin coloration in life. To facilitate the recognition and description of cryptic species previously hidden under the name P. ockendeni, we provide an amended diagnosis of this taxon based on external morphology and advertisement call of specimens recently collected nearby the type locality and additional localities in southwestern Amazonia.