Distribution and diversification of Adelphobates, emblematic poison frogs from Brazilian Amazonia

Adelphobates contains three species, and the inaccurate identification of A. quinquevittatus and the scarcity of records of A. castaneoticus complicate inference of their distributions; the latter species occurs in sympatry with A. galactonotus. Our objective was to revise the distributions of Adelphobates by compiling data and modeling habitat suitability, as range limits may be shaped by landscape features and biotic interactions. We initially analyzed the existence of operational taxonomic units within the nominal species and subsequently inferred the observed and potential distributions, taking into account the possible independent lineages for the three species, and we also generated a molecular timetree to understand the chronology of interspecific diversification events. Adelphobates quinquevittatus was found to have a more easterly distribution than previously described, and specimens with phenotypic variation were found to occur in areas inconsistent with the modeling, and A. castaneoticus was concentrated in the Tapajós-Xingu interfluve, surrounded by A. galactonotus. Models indicated that the right bank of the Xingu River is suitable for both species, indeed, both were found there. Despite Adelphobates species having their distributions delimited by major Amazonian rivers, estimated divergence times predate the formation of the modern river network, suggesting that other mechanisms were involved in their diversification.

A new nurse frog of the Allobates tapajos species complex (Anura: Aromobatidae) from the upper Madeira River, Brazilian Amazonia

Cryptic diversity is extremely common in widespread Amazonian anurans, but especially in nurse frogs of the genus Allobates. There is an urgent need to formally describe the many distinct but unnamed species, both to enable studies of their basic biology but especially to facilitate conservation of threatened environments in which many are found. Here, we describe through integrative taxonomy a new species of the Allobates tapajos species complex from the upper Madeira River, southwestern Amazonia. Species delimitation analyses based on molecular data are congruent and delimit five candidate species in addition to A. tapajos sensu stricto. The new species is recovered as sister to A. tapajos clade F, a candidate species from Teles-Pires River, southeastern Amazonia. The new species differs from nominal congeners in adult and larval morphology and in male advertisement call. Egg deposition sites differ between east and west banks of the upper Madeira River, but there is no evidence of corresponding morphologic or bioacoustic differentiation. The new species appears to be restricted to riparian forests; its known geographic range falls entirely within the influence zone of reservoirs of two large dams, which underscores the urgent need of a conservation assessment through long-term monitoring. This region harbors the richest assemblage of Allobates reported for Brazilian Amazonia, with six nominal species and four additional candidate species awaiting formal description.

A new Amazonian species of Allobates Zimmermann & Zimmermann, 1988 (Aromobatidae) with a trilled advertisement call

Background

Currently, 58 species are assigned to the genus Allobates, with 70% of its diversity described just in the last two decades, with many additional species likely unnamed. The continuous description of these new species represents a fundamental step for resolving the taxonomy and ensuring the future conservation of the genus.

Methods

Using molecular, acoustic, and morphological evidences, we describe a new species of Allobates from Teles Pires River region, southern Amazonia, and provide accounts on the population of A. tapajos found sympatrically with the new species.

Results

The new species is distinguished from its congeners by the coloration of thighs, venter, dorsum, and dark lateral stripe. It has four types of calls, with advertisement calls formed by relatively long trills with a mean duration of 2.29 s ± 0.65, mean of 39.93 notes ± 11.18 emitted at a mean rate of 17.49 ± 0.68 notes per second, and mean dominant frequency of 5,717 Hz ± 220.81. The genetic distance between the new species and its congeners in a fragment of the 16S mitochondrial fragment ranged between 13.2% (A. carajas) to 21.3% (A. niputidea). The sympatric Allobates population fits its morphology and acoustic with the nominal A. tapajos, but presents a relatively high genetic distance of nearly 6.5%, raising questions on the current taxonomy of this species.

A new nurse frog (Anura: Allobates) from Brazilian Amazonia with a remarkably fast multi-noted advertisement call

Nurse frogs (Aromobatidae: Allobates) are probably the most extensively studied genus by taxonomists in Brazilian Amazonia. The southwestern portion of Amazonia is the most species-rich: as many as seven species may occur in sympatry at a single locality. In this study, we describe a new species of nurse frog from this region. The description integrates data from larval and adult morphology, advertisement calls and DNA sequences. Allobates velocicantus sp. nov. is distinguished from other Allobates mainly by the absence of hourglass-shaped dark marks on the dorsum and dark transverse bars on the thigh; a throat that is white centrally and yellow marginally; basal webbing on toes II and III; finger I longer than finger II; and an advertisement call composed of 66–138 pulsed notes with a note duration of 5–13 ms, inter-note intervals of 10–18 ms and a dominant frequency of 5,512–6,158 Hz. Tadpoles of the new species have 3–4 short, rounded papillae on the anterior labium, 16–23 papillae on the posterior labium, and a labial keratodont row formula 2(2)/3(1). This is the fifth species of Allobates described from the state of Acre, southwestern Brazilian Amazonia.

A new tiny toad species of Amazophrynella (Anura: Bufonidae) from east of the Guiana Shield in Amazonia, Brazil

The combination of different approaches has successfully delimited new species within many Neotropical species complexes traditionally classified as a single nominal organism. Recent studies have shown that the Amazonian endemic genus Amazophrynella, currently composed of 12 small-sized species, could harbor several additional species. Based on morphology and molecular data, we describe a new species of Amazophrynella from east of the Guiana Shield, in Pará state, Brazil. The new species is characterized by having one of the biggest size of the genus (SVL of males 16.0–17.8 mm and females 22.9–24.4 mm), presence of a large palmar tubercle (occupying 2/4 of the palmar surface), 5.6–8.1% uncorrected p-distance from its sister clade (including A. teko, A. sp.1, and A. manaos) for the 16S mitochondrial gene, and 8.8% for the COI. The new species described here represents a newly discovered lineage. Of the 12 Amazophrynella species currently recognized, two were describe in the last century (A. bokermanni and A. minuta) and the remaining species were recently discovered and described (in the last six years), which underscores the degree to which species richness of Amazophrynella is underestimated.

Systematics and historical biogeography of Neotropical foam-nesting frogs of the Adenomera heyeri clade (Leptodactylidae), with the description of six new Amazonian species

A large proportion of the biodiversity of Amazonia, one of the most diverse rainforest areas in the world, is yet to be formally described. One such case is the Neotropical frog genus Adenomera. We here evaluate the species richness and historical biogeography of the Adenomera heyeri clade by integrating molecular phylogenetic and species delimitation analyses with morphological and acoustic data. Our results uncovered ten new candidate species with interfluve-associated distributions across Amazonia. In this study, six of these are formally named and described. The new species partly correspond to previously identified candidate lineages ‘sp. F’ and ‘sp. G’ and also to previously unreported lineages. Because of their rarity and unequal sampling effort of the A. heyeri clade across Amazonia, conservation assessments for the six newly described species are still premature. Regarding the biogeography of the A. heyeri clade, our data support a northern Amazonian origin with two independent dispersals into the South American Dry Diagonal. Although riverine barriers have a relevant role as environmental filters by isolating lineages in interfluves, dispersal rather than vicariance must have played a central role in the diversification of this frog clade.

Variability in anuran advertisement call: a multi-level study with 15 species of monkey tree frogs (Anura, Phyllomedusidae)

Understanding the variability of acoustic signals is a first important step for the comprehension of the evolutionary processes that led to current diversity. Herein, we evaluate the variability of the advertisement call of the phyllomedusid species from the genera Phyllomedusa Wagler, 1830 and Pithecopus Cope, 1866 at different levels: intra-individual, intra-population, inter-population, intra-species, and inter-specific. An analysis of coefficients of variation showed a continuum of variability between the acoustic parameters analyzed, from static to highly dynamic. The majority of the variation was attributed to the inter-specific level, while call parameters at the intra-individual level varied the least. However, each parameter behaved differently with call interval being the most variable across all levels. Most temporal acoustic parameters were affected by environmental temperature, while pulse rate and dominant frequency were strongly influenced by body size. Only pulse rate was correlated to the geographic distance between populations, while all parameters presented a significant phylogenetic signal. Based on these results, we discuss the possible importance of different evolutionary forces and the usage of vocalizations for taxonomic purposes.

Araújo M, Kaefer IL, Lima AP. 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.

Dwarf geckos and giant rivers: the role of the São Francisco River in the evolution of Lygodactylus klugei (Squamata: Gekkonidae) in the semi-arid Caatinga of north-eastern Brazil

Species diversification can be strongly influenced by geomorphological features, such as mountains, valleys and rivers. Rivers can act as hard or soft barriers to gene flow depending on their size, speed of flow, historical dynamics and regional topographical characteristics. The São Francisco River (SFR) is the largest perennial river in the Caatinga biome in north-eastern Brazil and has been considered a barrier to gene flow and dispersal. Herein, we evaluated the role of the SFR on the evolution of Lygodactylus klugei, a small gecko from the Caatinga. Using a single-locus species delimitation method (generalized mixed Yule coalescent), we defined lineages (haploclades). Subsequently, we evaluated the role of the SFR in structuring genetic diversity in this species using a multilocus approach to quantify migration across margins. We also evaluated genetic structure based on nuclear markers, testing the number of populations found through an assignment test (STRUCTURE) across the species distribution. We recovered two mitochondrial lineages structured with respect to the SFR, but only a single population was inferred from nuclear markers. Given that we detected an influence of the SFR only on mitochondrial markers, we suggest that the current river course has acted as a relatively recent geographical barrier for L. klugei, for ~450 000 years.

Tangled banks: A landscape genomic evaluation of Wallace's Riverine barrier hypothesis for three Amazon plant species

Wallace's Riverine Barrier hypothesis is one of the earliest biogeographic explanations for Amazon speciation, but it has rarely been tested in plants. In this study, we used three woody Amazonian plant species to evaluate Wallace's Hypothesis using tools of landscape genomics. We generated unlinked single-nucleotide polymorphism (SNP) data from the nuclear genomes of 234 individuals (78 for each plant species) across 13 sampling sites along the Rio Branco, Brazil, for Amphirrhox longifolia (8,075 SNPs), Psychotria lupulina (9,501 SNPs) and Passiflora spinosa (14,536 SNPs). Although significantly different migration rates were estimated between species, the population structure data do not support the hypothesis that the Rio Branco-an allopatric barrier for primates and birds-is a significant genetic barrier for Amphirrhox longifolia, Passiflora spinosa or Psychotria lupulina. Overall, we demonstrated that medium-sized rivers in the Amazon Basin, such as the Rio Branco, are permeable barriers to gene flow for animal-dispersed and animal-pollinated plant species.