Sampling design may obscure species–area relationships in landscape-scale field studies

We investigated 1) the role of area per se in explaining anuran species richness on reservoir forest islands, after controlling for several confounding factors. We also assessed 2) how sampling design affects the inferential power of island species–area relationships (ISARs) aiming to 3) provide guidelines to yield reliable estimates of area-induced species losses in patchy systems. We surveyed anurans with autonomous recording units at 151 plots located on 74 islands and four continuous forest sites at the Balbina Hydroelectric Reservoir landscape, central Brazilian Amazonia. We applied semi-log ISAR models to assess the effect of sampling design on the fit and slope of species–area curves. To do so, we subsampled our surveyed islands following both a 1) stratified and 2) non-stratified random selection of 5, 10, 15, 20 and 25 islands covering 1) the full range in island size (0.45–1699 ha) and 2) only islands smaller than 100 ha, respectively. We also compiled 25 datasets from the literature to assess the generality of our findings. Island size explained ca half of the variation in species richness. The fit and slope of species–area curves were affected mainly by the range in island size considered, and to a very small extent by the number of islands surveyed. In our literature review, all datasets covering a range of patch sizes larger than 300 ha yielded a positive ISAR, whereas the number of patches alone did not affect the detection of ISARs. We conclude that 1) area per se plays a major role in explaining anuran species richness on forest islands within an Amazonian anthropogenic archipelago; 2) the inferential power of island species–area relationships is severely degraded by sub-optimal sampling designs; 3) at least 10 habitat patches spanning three orders of magnitude in size should be surveyed to yield reliable species–area estimates in patchy systems

The peculiar breeding biology of the Amazonian frog Allobates subfolionidificans (Aromobatidae)

Allobates subfolionidificans is a vulnerable and endemic leaf-litter frog from the state of Acre, Brazilian Amazonia. We monitored a population of A. subfolionidificans through regular censuses and mark-recapture of 181 individuals during an entire breeding season to characterize its reproductive behavior. The space use of A. subfolionidificans individuals differed between sexes, with males using smaller and more segregated spaces. Males defended territories and were aggressive against same-sex individuals, which was not the case in females. The daily cycle of calling activity showed peaks in the morning and in the afternoon, and the occurrence of reproductive events was positively correlated with monthly rainfall. The breeding behavior comprised vocal and tactile interactions, although the species lacked reproductive amplexus. Egg and larvae attendance, as well as tadpole transport to water environments was performed mostly by males but occasionally by females, probably in cases of desertion by the father. This species is characterized by performing courtship, mating, oviposition, as well as egg and larvae attendance exclusively on the under surface of leaves, a unique behavior among members of the superfamily Dendrobatoidea

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 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

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

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