Not just the river: Genes, shapes, and sounds reveal population-structured diversification in the Amazonian frog Allobates tapajos (Dendrobatoidea)

In the Amazon basin, the distribution of many vertebrate species is delimited by large rivers, which are frequently considered as biogeographical barriers strongly related to the origin and maintenance of the elevated biodiversity found in the region. In this study, we conducted a phylogeographical investigation of the effect of the Tapajós River on multiple classes of genotypic and phenotypic characters in a species of frog, Allobates tapajos. We sampled populations throughout the known distributional range of the species on both margins of the middle and lower sections of the river. We obtained fragments of mitochondrial (16S) and nuclear (RAG1) genes, as well as external morphometric measurements and advertisement call acoustic parameters of 48 individuals from six localities (populations). While the nuclear marker was monomorphic across the geographic distribution of A. tapajos, the mitochondrial fragment revealed low genetic distances accompanied by high spatial structuring, with restricted and absent haplotype sharing between populations and opposite river margins, respectively. Cladogenetic events were concentrated in the Pleistocene epoch, the time period corresponding to the establishment of the Tapajós River drainage. Acoustic parameters diverged between river margins, a pattern not observed in relation to the morphological markers analysed. There was no correlation in the variability pattern of the different classes of characters between them or in relation to linear geographic distance among populations. In addition, discriminant function analyses correctly assigned most of the individuals to their populations based on phenotypic characters. Our results show that the distribution of the variability within A. tapajos is affected not only by the transposition of a historical riverine barrier but also mostly by an elevated genotypic and phenotypic structure at the population level. © 2017 The Linnean Society of London

The tadpole of Osteocephalus cabrerai (Anura: Hylidae) from central Amazonia, Brazil

Herein we describe the tadpoles of Osteocephalus cabrerai based on 37 individuals of eight different development stages. We provide comments on spawning sites and breeding period, and compare these tadpoles with those of congeners. The tadpole of O. cabrerai (Stage 39) is characterized by an ovoid body, elongated in lateral view and oval in dorsal view. The snout is rounded, the nostrils oval and the eyes lateral. The tail length is 67% of total length. The larva has a single, sinistral spiracle that is ventrolateral in position. The short vent tube is dextral and attached to the ventral fin. The anteroventral oral disc has marginal and submarginal papillae and a labial tooth row formula 2(2)/6(1). Tadpoles inhabit streams in terra firme forest. © 2011 Departamento de Ciências Biológicas - ESALQ - USP

The lizards along the road BR-319 in the Purus-Madeira interfluve, Brazilian Amazonia (Squamata, Lacertilia)

Here we present data on the identity and geographic distribution of lizard taxa in the Purus-Madeira interfluve, along the road BR-319 in Brazilian Amazonia. We sampled 10 modules located at least 40 kilometres from each other. Data collection was performed through active search on vegetation and leaf-litter along 250 m-long transects, and by occasional encounters. Twenty-five taxa from 16 genera and eight families were recorded. The present assessment reinforces the importance of this area to the conservation of Amazonian lizards and should be considered as basis for studies of ecology and environmental impact regarding lizard communities in this threatened region. © 2019, Societas Europaea Herpetologica. All rights reserved

Acoustic interference and recognition space within a complex assemblage of dendrobatid frogs

In species-rich assemblages of acoustically communicating animals, heterospecific sounds may constrain not only the evolution of signal traits but also the much less-studied signal-processing mechanisms that define the recognition space of a signal. To test the hypothesis that the recognition space is optimally designed, i.e., that it is narrower toward the species that represent the higher potential for acoustic interference, we studied an acoustic assemblage of 10 diurnally active frog species. We characterized their calls, estimated pairwise correlations in calling activity, and, to model the recognition spaces of five species, conducted playback experiments with 577 synthetic signals on 531 males. Acoustic co-occurrence was not related to multivariate distance in call parameters, suggesting a minor role for spectral or temporal segregation among species uttering similar calls. In most cases, the recognition space overlapped but was greater than the signal space, indicating that signal-processing traits do not act as strictly matched filters against sounds other than homospecific calls. Indeed, the range of the recognition space was strongly predicted by the acoustic distance to neighboring species in the signal space. Thus, our data provide compelling evidence of a role of heterospecific calls in evolutionarily shaping the frogs' recognition space within a complex acoustic assemblage without obvious concomitant effects on the signal

The costs of evaluating species densities and composition of snakes to assess development impacts in Amazonia

Studies leading to decision-making for environmental licensing often fail to provide accurate estimates of diversity. Measures of snake diversity are regularly obtained to assess development impacts in the rainforests of the Amazon Basin, but this taxonomic group may be subject to poor detection probabilities. Recently, the Brazilian government tried to standardize sampling designs by the implementation of a system (RAPELD) to quantify biological diversity using spatiallystandardized sampling units. Consistency in sampling design allows the detection probabilities to be compared among taxa, and sampling effort and associated cost to be evaluated. The cost effectiveness of detecting snakes has received no attention in Amazonia. Here we tested the effects of reducing sampling effort on estimates of species densities and assemblage composition. We identified snakes in seven plot systems, each standardised with 14 plots. The 250 m long centre line of each plot followed an altitudinal contour. Surveys were repeated four times in each plot and detection probabilities were estimated for the 41 species encountered. Reducing the number of observations, or the size of the sampling modules, caused significant loss of information on species densities and local patterns of variation in assemblage composition. We estimated the cost to find a snake as $ 120 U.S., but general linear models indicated the possibility of identifying differences in assemblage composition for half the overall survey costs. Decisions to reduce sampling effort depend on the importance of lost information to target-issues, and may not be the preferred option if there is the potential for identifying individual snake species requiring specific conservation actions. However, in most studies of human disturbance on species assemblages, it is likely to be more cost-effective to focus on other groups of organisms with higher detection probabilities. © 2014 Fraga et al

Distribution extension of Hyalinobatrachium cappellei (van Lidth de Jeude, 1904) (Anura: Centrolenidae) across Central Amazonia

We report the occurrence of the centrolenid frog Hyalinobatrachium cappellei in Careiro, Amazonas, Brazil (Central Amazonia). Our records reduce a gap of approximately 1,500 km between the closest known records for this glassfrog, and confirm H. cappellei as geographically widespread in the Amazon Basin. © 2012 Check List and Authors

Contrasting Patterns of Gene Flow for Amazonian Snakes That Actively Forage and Those That Wait in Ambush

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. © The American Genetic Association 2017. All rights reserved

A new species of Amazonian snouted treefrog (Hylidae: Scinax) with description of a novel species-habitat association for an aquatic breeding frog

The genus Scinax is one of the most specious genera of treefrogs of the family Hylidae. Despite the high number of potential new species of Scinax revealed in recent studies, the rate of species descriptions for Amazonia has been low in the last decade. A potential cause of this low rate may be the existence of morphologically cryptic species. Describing new species may not only impact the taxonomy and systematics of a group of organisms but also benefit other fields of biology. Ecological studies conducted in megadiverse regions, such as Amazonia, often meet challenging questions concerning insufficient knowledge of organismal alpha taxonomy. Due to that, detecting specieshabitat associations is dependent on our ability to properly identify species. In this study, we first provide a description of a new species (including its tadpoles) of the genus Scinax distributed along heterogeneous landscapes in southern Amazonia; and secondly assess the influence of environmental heterogeneity on the new species' abundance and distribution. Scinax ruberoculatus sp. nov. differs from all nominal congeners by its small size (SVL 22.6-25.9mmin males and 25.4-27.5mmin females), by having a dark brown spot on the head and scapular region shaped mainly like the moth Copiopteryx semiramis (or a human molar in lateral view, or a triangle), bicolored reddish and grey iris, snout truncate in dorsal view, bilobate vocal sac in males, by its advertisement call consisting of a single pulsed note with duration of 0.134-0.331 s, 10-23 pulses per note, and dominant frequency 1,809-1,895 Hz. Both occurrence and abundance of the new species are significantly influenced by silt content in the soil. This finding brings the first evidence that edaphic factors influence species-habitat association in Amazonian aquatic breeding frogs. © 2018 Ferrão et al

Hierarchical effects of historical and environmental factors on lizard assemblages in the upper Madeira River, Brazilian Amazonia

Investigating the role of historical and ecological factors structuring assemblages is relevant to understand mechanisms and processes affecting biodiversity across heterogeneous habitats. Considering that community assembly often involves scale-dependent processes, different spatial scales may reveal distinct factors structuring assemblages. In this study we use arboreal and leaf-litter lizard abundance data from 83 plots to investigate assemblage spatial structure at two distinct scales in southwestern Brazilian Amazonia. At a regional scale, we test the general hypothesis that the Madeira River acts as a barrier to dispersal of some lizard species, which results in distinct assemblages between river banks. At a local scale, we test the hypothesis that assemblages are not evenly distributed across heterogeneous habitats but respond to a continuum of inadequate-to-optimal portions of environmental predictors. Our results show that regional lizard assemblages are structured by the upper Madeira River acting as a regional barrier to 29.62% of the species sampled. This finding suggests species have been historically isolated at one of the river banks, or that distinct geomorphological features influence species occurrence at each river bank. At a local scale, different sets of environmental predictors affected assemblage composition between river banks or even along a river bank. These findings indicate that environmental filtering is a major cause of lizard assemblage spatial structure in the upper Madeira River, but predictor variables cannot be generalized over the extensive (nearly 500 km) study area. Based on a single study system we demonstrate that lizard assemblages along the forests near the banks of the upper Madeira River are not randomly structured but respond to multiple factors acting at different and hierarchical spatial scales. © 2020 Marques Peixoto et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited