Comparative skull osteology of Amphisbaena arda and Amphisbaena vermicularis (Squamata: Amphisbaenidae).

The skull anatomy of amphisbaenians directly influences their capacity to burrow and is crucial for the study of their systematics, which ultimately contributes to our comprehension of their evolution and ecology. In this study, we employed three-dimensional X-ray computed tomography to provide a detailed description and comprehensive comparison of the skull anatomy of two amphisbaenian species with similar external morphology, Amphisbaena arda and Amphisbaena vermicularis. Our findings revealed some differences between the species, especially in the sagittal crest of the parietal bone, the ascendant process, and the transverse occipital crest of the occipital complex. We also found intraspecific variation within A. vermicularis, with some specimens displaying morphology that differed from their conspecifics but not from A. arda. The observed intraspecific variation within A. vermicularis cannot be attributed to soil features because all specimens came from the same locality. Specimen size and soil type may play a role in the observed differences between A. arda and A. vermicularis, as the single A. arda specimen is the largest of our sample and soil type and texture differ between the collection sites of the two species.

Molecular phylogeny and biogeography of the dwarf boas of the family Tropidophiidae (Serpentes: Alethinophidia)

Although present in the South American continent, dwarf boas (Tropidophiidae) show their greatest extant diversification in the Caribbean region, reaching their highest diversity in Cuba. Despite their remarkable species richness, phylogenetic affinities among species of Tropidophis and Trachyboa are still poorly known. Here, we provide a multi-locus phylogenetic hypothesis of the family that includes 25 of the 37 known continental and insular species, including most of its highly diverse Cuban endemic radiation (16 out of 17 species sampled). We also provide a time-calibrated tree derived from our molecular data. Our phylogenetic results indicate that the genus Tropidophis and its mainland and Cuban radiations are paraphyletic, while the Caribbean radiation forms a well-supported clade. We therefore synonymize Trachyboa with Tropidophis and provide new definitions for the species groups. Our time-calibrated tree suggests that tropidophiids originated along the northwestern Andean region of continental South America, diverging from its known sister-group genus Anilius during the late Cretaceous. The Atlantic Rainforest radiation diverged from the Andean radiation during the late Eocene. A mainland tropidophiid ancestor subsequently dispersed from northern South America to the Caribbean region in the latest Eocene. Dispersal likely took place through a near-continuous terrestrial land bridge that connected South America to the Greater Antilles during the late Eocene to early Oligocene (35–33 Ma). The existence of this land bridge, whether formed by the Aves Ridge (GAARlandia Hypothesis) or by a more southernly positioned landmass connecting the Greater Antilles and the northern Lesser Antilles Ridge (GRANoLA hypothesis), remains a topic of debate, which we address in this paper. After that main dispersal event, West Indian tropidophiids underwent over ten speciation events, rapidly colonizing the Caribbean islands. We also address the vertebral morphology of fossil and extant Tropidophiidae, with our observations challenging the current classification of several fossil taxa within crown-Tropidophiidae.

Comparing morphological and secretory aspects of cephalic glands among the New World coral snakes brings novel insights on their biological roles.

Oral and other cephalic glands have been surveyed by several studies with distinct purposes. Despite the wide diversity and medical relevance of the New World coral snakes, studies focusing on understanding the biological roles of the glands within this group are still scarce. Specifically, the venom glands of some coral snakes were previously investigated but all other cephalic glands remain uncharacterized. In this sense, performing morphological and molecular analysis of these glands may help better understand their biological role. Here, we studied the morphology of the venom, infralabial, rictal, and harderian glands of thirteen species of Micrurus and Micruroides euryxanthus. We also performed a molecular characterization of these glands from selected species of Micrurus using transcriptomic and proteomic approaches. We described substantial morphological variation in the cephalic glands of New World coral snakes and structural evidence for protein-secreting cells in the inferior rictal glands. Our molecular analysis revealed that the venom glands, as expected, are majorly devoted to toxin production, however, the infralabial and inferior rictal glands also expressed some toxin genes at low to medium levels, despite the marked morphological differences. On the other hand, the harderian glands were dominated by the expression of lipocalins, but do not produce toxins. Our integrative analysis, including the prediction of biological processes and pathways, helped decipher some important traits of cephalic glands and better understand their biology.

Genomic evidence reveals intraspecific divergence of the hot-spring snake (Thermophis baileyi), an endangered reptile endemic to the Qinghai-Tibet plateau.

Understanding how and why species evolve requires knowledge on intraspecific divergence. In this study, we examined intraspecific divergence in the endangered hot-spring snake (Thermophis baileyi), an endemic species on the Qinghai-Tibet Plateau (QTP). Whole-genome resequencing of 58 sampled individuals from 15 populations was performed to identify the drivers of intraspecific divergence and explore the potential roles of genes under selection. Our analyses resolved three groups, with major intergroup admixture occurring in regions of group contact. Divergence probably occurred during the Pleistocene as a result of glacial climatic oscillations, Yadong-Gulu rift, and geothermal fields differentiation, while complex gene flow between group pairs reflected a unique intraspecific divergence pattern on the QTP. Intergroup fixed loci involved selected genes functionally related to divergence and local adaptation, especially adaptation to hot spring microenvironments in different geothermal fields. Analysis of structural variants, genetic diversity, inbreeding, and genetic load indicated that the hot-spring snake population has declined to a low level with decreased diversity, which is important for the conservation management of this endangered species. Our study demonstrated that the integration of demographic history, gene flow, genomic divergence genes, and other information is necessary to distinguish the evolutionary processes involved in speciation.

Comparing morphological and secretory aspects of cephalic glands among the New World coral snakes brings novel insights on their biological roles

Oral and other cephalic glands have been surveyed by several studies with distinct purposes. Despite the wide diversity and medical relevance of the New World coral snakes, studies focusing on understanding the biological roles of the glands within this group are still scarce. Specifically, the venom glands of some coral snakes were previously investigated but all other cephalic glands remain uncharacterized. In this sense, performing morphological and molecular analysis of these glands may help better understand their biological role. Here, we studied the morphology of the venom, infralabial, rictal, and harderian glands of thirteen species of Micrurus and Micruroides euryxanthus. We also performed a molecular characterization of these glands from selected species of Micrurus using transcriptomic and proteomic approaches. We described substantial morphological variation in the cephalic glands of New World coral snakes and structural evidence for protein-secreting cells in the inferior rictal glands. Our molecular analysis revealed that the venom glands, as expected, are majorly devoted to toxin production, however, the infralabial and inferior rictal glands also expressed some toxin genes at low to medium levels, despite the marked morphological differences. On the other hand, the harderian glands were dominated by the expression of lipocalins, but do not produce toxins. Our integrative analysis, including the prediction of biological processes and pathways, helped decipher some important traits of cephalic glands and better understand their biology.

Phylogenetic and morphological evidence reveals the association between diet and the evolution of the venom delivery system in Neotropical goo-eating snakes

Advanced endoglyptodont snakes share a complex but homologous venom delivery system associated with the upperjaw and its dentition. Recently, a remarkable novel lower jaw venom delivery system was described for the Neotropicaldipsadine radiation of goo-eating snakes. While most dipsadines are opistoglyphous and exhibit large, mainly serousvenom glands associated with the upper jaw and supralabial glands, goo-eating dipsadine snakes are aglyphous and lackserous upper labial venom glands. Here, we provide new morphological and histological information on the oral glandsand maxillary dentition of representatives of the major lineages of dipsadines that help trace the evolutionary steps thatshaped the venom delivery system of dipsadines. We performed a maximum likelihood analysis on a molecular datasetthat includes 443 terminals and seven loci. Our results show that goo-eating dipsadines form a monophyletic assemblagethat includes the genusAdelphicosfor the first time, along withGeophis,Atractus,Ninia,Chersodromus,Tropidodipsas,Sibon, andDipsas. We also provide the first evidence of a complete shift from an upper jaw to a lower jaw venomdelivery system associated with their specialized feeding behaviour. Unlike other dipsadines who exhibit typicalendoglyptodont anteroposteriorly ridged posterior maxillary teeth, goo-eating dipsadines have uniform lateromediallyridged teeth throughout their maxilla. Our results indicate that the loss of the endoglyptodont venom delivery systemoccurred in the most recent common ancestor of goo-eating dipsadines, probably resulting from the loss of theembryonic posterior maxillary lamina responsible for the development of the venom delivery system.

Revealing the cryptic diversity of the widespread and poorly known South American blind snake genus Amerotyphlops (Typhlopidae: Scolecophidia) through integrative taxonomy

Morphological stasis is generally associated with relative constancy in ecological pressures throughout time, producing strong stabilizing selection that retains similar shared morphology. Although climate and vegetation are commonly the main key factors driving diversity and phenotypic diversification in terrestrial vertebrates, fossorial organisms have their morphology mostly defined by their fossorial lifestyle. Among these secretive fossorial organisms, blind snakes of the South American genus Amerotyphlops are considered poorly studied when compared to other taxa. Here, we evaluate the cryptic diversity of Amerotyphlops using phylogenetic and multivariate approaches. We based our phylogenetic analysis on a molecular dataset composed of 12 gene fragments (eight nuclear and four mitochondrial) for 109 species of Typhlopidae. The multivariate analysis was implemented using 36 morphological variables for 377 specimens of Amerotyphlops. Additionally, we contrast our phylogenetic result with the morphological variation found in cranial, external and hemipenial traits. Our phylogenetic results recovered with strong support the following monophyletic groups within Amerotyphlops: (1) a clade formed by A. tasymicris and A. minuisquamus; (2) a clade composed of A. reticulatus; (3) a north-eastern Brazilian clade including A. yonenagae, A. arenensis, A. paucisquamus and A. amoipira; and (4) a clade composed of A. brongersmianus and a complex of cryptic species. Based on these results we describe four new species of Amerotyphlops from north-eastern and south-eastern Brazil, which can be distinguished from the morphologically similar species, A. brongersmianus and A. arenensis.

The systematics of Tachymenini (Serpentes, Dipsadidae): an updated classification based on molecular and morphological evidence

Despite the recent advances in the systematics of snakes, the diversity of several Neotropical groups of species remains poorly understood. The lack of studies focused on the phylogenetic relationship within most of the 20 tribes of Dipsadidae precludes a better understanding of the evolution of this diverse family. Here, we present a comprehensive phylogenetic analysis of Tachymenini, a heterogeneous tribe that comprises 36 viviparous species of dipsadids, grouped in seven genera based on morphological similarities. The tribe is widely distributed throughout South America presenting very distinctive phenotypes, habitats, and behaviours. The phylogenetic relationship among tachymenins is a well-recognized challenge regarding the systematics of the South American dipsadids. The similar morphotype of some generalist species, combined with the very derived morphology of some strict specialists, creates a complexity of traits that has prevented the comprehension of the systematics of the group. To address such a challenge, we combine molecular (six loci) and morphological (70 characters) datasets in an integrative phylogenetic approach. The resultant phylogenetic trees indicate, with strong support, that three of the seven current recognized genera (Tachymenis, Tomodon, and Thamnodynastes) are non-monophyletic and, consequently, we propose a new systematic arrangement for Tachymenini. We revalidate two genera, Dryophylax and Mesotes, and we describe three additional monotypic genera, Apographon gen. n., Tachymenoides gen. n., and Zonateres gen. n. to accommodate Tomodon orestes, Tachymenis affinis, and Thamnodynastes lanei, respectively. We also include Tomodon ocellatus and Pseudotomodon trigonatus in Tachymenis and describe a new genus, Galvarinus gen. n., to accommodate the Tachymenis chilensis species group. Furthermore, we also provide an evolutionary scenario for the speciation events based on a time-calibrated tree, commenting on the diversification and origin of the tribe, and on the probable existence of undescribed species of Mesotes and Dryophylax.

The skull of Sanajeh indicus, a Cretaceous snake with an upper temporal bar, and the origin of ophidian wide-gaped feeding

Recent phylogenetic analyses differ in their interpretations of the origin and interrelationships of snakes, resulting in polarized views of snake ecology, habit and acquisition of features associated with wide-gaped feeding (macrostomy). Here, we report a new specimen of the Late Cretaceous nest predator Sanajeh indicus that helps to resolve the origin of macrostomy. The new specimen preserves an ossified upper temporal bar and a posteriorly expanded otooccipital region that lacks a free-ending supratemporal bone and retains a lizard-like palatomaxillary arch that allows limited movements during swallowing. Phylogenetic analyses of a large-scale total evidence dataset resolve Sanajeh near the base of Pan-Serpentes, as the sister group of Najash, Dinilysia and crown-group Serpentes. The Cretaceous Tetrapodophis and Coniophis represent the earliest-diverging members of Pan-Serpentes. The Cretaceous hindlimbed pachyophiids and Cenozoic Australian ‘madtsoiids’ are inside crown Alethinophidia, whereas mosasaurs are recovered invariably within anguimorphs. Our results suggest that the wide-gape condition in mosasaurs and snakes might have evolved independently, as functionally distinct mechanisms of prey ingestion. The intermediate morphology preserved in Sanajeh indicates that ingestion of large prey items (macrophagy) preceded wide-gaped, unilateral feeding (macrostomy), which appeared 35 Myr later, in the common ancestor of pachyophiids, Cenozoic Australian ‘madtsoiids’ and alethinophidians.

Reassessing the systematics of Leptodeira (Serpentes, Dipsadidae) with emphasis in the South American species

Within the diverse subfamily Dipsadinae, Imantodini represents one of the few groups distributed in North, Central and South America. The tribe comprises the genera Leptodeira and Imantodes, from which Leptodeira is the most diverse, including 15 species and 11 subspecies, distributed from southern USA to central Argentina. Taxonomy and affinities among these taxa are poorly resolved, and the phylogenetic relationships among the South American diversity were never properly assessed before. Here, we investigate the phylogenetic relationships and the taxonomic status of Leptodeira spp. based on a comprehensive multilocus dataset with emphasis in the South American radiation. Besides assessing the phylogenetic relationship and species cohesion, we also evaluate the morphological variation among the South American diversity of Leptodeira. Our results support the monophyly of Imatodini and Leptodeira, while indicating that several individuals classified as Leptodeira annulata and L. septentrionalis do not cluster together within their respective species. Moreover, specimens identified as belonging to the subspecies L. a. annulata, L. a. cussiliris, L. s. ornata and L. s. polysticta do not group together suggesting the current classification includes non-natural groups. The analysis of morphological evidence also supports the phylogenetics results, indicating that several clades can be recognized as evolutionary units presenting distinct phenotypes. To equate the taxonomy to our results, we propose a new taxonomic arrangement for Leptodeira in which we are: (1) redefining the composition of L. annulata and L. septentrionalis; (2) elevating five subspecies to species level; (3) revalidating one species; (4) recognizing four species complexes; and (5) indicating the presence of hidden diversity (probably four undescribed species). Finally, we describe a new species (Leptodeira tarairiu sp. nov.) from the open formations of South America (Cerrado and Caatinga), and we provide detailed redescriptions for all South American species of Leptodeira.

Contributions to ophiology in Zootaxa 20012020: patterns and trends.

There are currently 3,900 recognized, extant snake species belonging to 529 genera globally (Uetz et al. 2021; this study), making snakes one of the most diverse major groups of squamates. Of the 665 currently recognized species that were described between 2001 and 2020 (a ~17% increase in total species), ~34% of these (226 species) were described in Zootaxa. This number does not include species resurrected from synonymy. The other ~66% (439) species were described in 105 other journals, bulletins or books (Fig.1a). Overall, the number of new snake species described every year is gradually increasing, and 40% of the new species described since 2011 were published in Zootaxa. Following Zootaxa, the second ranked journal, with 37 described species since 2001, is Herpetologica (Fig. 2). Anecdotally, the choice of Zootaxa as a publication outlet for new species descriptions by most authors is based on speed of publication post-acceptance, publication free of charge, relatively unconstrained number of papers published per year, relatively unconstrained manuscript length, expert section editors and reviewers, and consolidated scientometric parameters.

A new species of emThamnodynastes/em Wagler, 1830 from western Amazonia, with notes on morphology for members of the emThamnodynastes/em empallidus/em group (Serpentes, Dipsadidae, Tachymenini).

The genus Thamnodynastes is the most diverse within the tribe Tachymenini, with an extensive and complex taxonomic history. The brief descriptions and lack of robust diagnostic characters are the main sources for identification errors and for the difficulty to assess the diversity estimates of the genus. The Thamnodynastes pallidus group was briefly designated to encompass the most arboreal species of the genus, with thinner bodies and longer tails: T. pallidus, T. longicaudus, T. sertanejo, and a fourth undescribed species. After its designation, no other paper addressed this group and its morphological variation, especially for the hemipenis, is still undetermined. After the analysis of all species of Thamnodynastes we were able to corroborate the distinctiveness of the T. pallidus group and to accurately diagnose its fourth species from the western portion of the Amazonia lowlands. The new species is distinguishable from all congeners, except T. sertanejo, by the absence of ventral longitudinal stripes, 17/17/11 dorsal scale rows, and dorsal dark brown blotches on the anterior third of the body. The new species is distinguished from T. sertanejo by the higher number of subcaudals, lower number of ventrals, and smaller body and head sizes. We also provide additional diagnostic features for the Thamnodynastes pallidus group, including new data on hemipenial variation. Finally, we briefly discuss the defensive behavior and morphological characters associated with arboreality in members of the T. pallidus species group.

A new species of Thamnodynastes Wagler, 1830 from western Amazonia, with notes on morphology for members of the Thamnodynastes pallidus group (Serpentes, Dipsadidae, Tachymenini)

The genus Thamnodynastes is the most diverse within the tribe Tachymenini, with an extensive and complex taxonomic history. The brief descriptions and lack of robust diagnostic characters are the main sources for identification errors and for the difficulty to assess the diversity estimates of the genus. The Thamnodynastes pallidus group was briefly designated to encompass the most arboreal species of the genus, with thinner bodies and longer tails: T. pallidus, T. longicaudus, T. sertanejo, and a fourth undescribed species. After its designation, no other paper addressed this group and its morphological variation, especially for the hemipenis, is still undetermined. After the analysis of all species of Thamnodynastes we were able to corroborate the distinctiveness of the T. pallidus group and to accurately diagnose its fourth species from the western portion of the Amazonia lowlands. The new species is distinguishable from all congeners, except T. sertanejo, by the absence of ventral longitudinal stripes, 17/17/11 dorsal scale rows, and dorsal dark brown blotches on the anterior third of the body. The new species is distinguished from T. sertanejo by the higher number of subcaudals, lower number of ventrals, and smaller body and head sizes. We also provide additional diagnostic features for the Thamnodynastes pallidus group, including new data on hemipenial variation. Finally, we briefly discuss the defensive behavior and morphological characters associated with arboreality in members of the T. pallidus species group.

A morphological and molecular study of Hydrodynastes gigas (Serpentes, Dipsadidae), a widespread species from South America.

BACKGROUND: Studies with integrative approaches (based on different lines of evidence) are fundamental for understanding the diversity of organisms. Different data sources can improve the understanding of the taxonomy and evolution of snakes. We used this integrative approach to verify the taxonomic status of Hydrodynastes gigas (Duméril, Bibron & Duméril, 1854), given its wide distribution throughout South America, including the validity of the recently described Hydrodynastes melanogigas Franco, Fernandes & Bentim, 2007. METHODS: We performed a phylogenetic analysis of Bayesian Inference with mtDNA 16S and Cytb, and nuDNA Cmos and NT3 concatenated (1,902 bp). In addition, we performed traditional morphometric analyses, meristic, hemipenis morphology and coloration pattern of H. gigas and H. melanogigas. RESULTS: According to molecular and morphological characters, H. gigas is widely distributed throughout South America. We found no evidence to support that H. gigas and H. melanogigas species are distinct lineages, therefore, H. melanogigas is a junior synonym of H. gigas. Thus, the melanic pattern of H. melanogigas is the result of a polymorphism of H. gigas. Melanic populations of H. gigas can be found in the Tocantins-Araguaia basin.

Pythons in the Eocene of Europe reveal a much older divergence of the group in sympatry with boas.

Extant large constrictors, pythons and boas, have a wholly allopatric distribution that has been interpreted largely in terms of vicariance in Gondwana. Here, we describe a stem pythonid based on complete skeletons from the early-middle Eocene of Messel, Germany. The new species is close in age to the divergence of Pythonidae from North American Loxocemus and corroborates a Laurasian origin and dispersal of pythons. Remarkably, it existed in sympatry with the stem boid Eoconstrictor. These occurrences demonstrate that neither dispersal limitation nor strong competitive interactions were decisive in structuring biogeographic patterns early in the history of large, hyper-macrostomatan constrictors and exemplify the synergy between phylogenomic and palaeontological approaches in reconstructing past distributions.

Multilocus phylogeny of Paratelmatobiinae (Anura: Leptodactylidae) reveals strong spatial structure and previously unknown diversity in the Atlantic Forest hotspot.

The Brazilian Atlantic Forest harbors high levels of anuran diversity and endemism, including several taxa restricted to small geographic ranges. Here, we provide a multilocus phylogeny for Paratelmatobiinae, a leptodactylid subfamily composed of small-ranged species distributed in the Brazilian Atlantic Forest and in the campo rupestre ecosystem. We performed Bayesian inference and maximum likelihood analyses using three mitochondrial and five nuclear markers, and a matrix comprising a broad taxonomic sampling. We then delimitated independently evolving lineages within the group. We recovered Paratelmatobiinae and each of its four genera as monophyletic and robustly supported. Five putatively new species included in our analyses were unambiguously supported in the phylogenetic trees and delimitation analyses. We also recovered other deeply divergent and geographically structured lineages within the four genera of Paratelmatobiinae. Our estimation of divergence times indicates that diversification in the subfamily began in the Eocene and continued until the Pleistocene. We discuss possible scenarios of diversification for the four genera of Paratelmatobiinae, and outline the implications of our findings for taxonomy and conservation.

Phylogenomics, Biogeography, and Morphometrics Reveal Rapid Phenotypic Evolution in Pythons After Crossing Wallace's Line.

Ecological opportunities can be provided to organisms that cross stringent biogeographic barriers towards environments with new ecological niches. Wallace's and Lyddeker's lines are arguably the most famous biogeographic barriers, separating the Asian and Australo-Papuan biotas. One of the most ecomorphologically diverse groups of reptiles, the pythons, is distributed across these lines, and are remarkably more diverse in phenotype and ecology east of Lydekker's line in Australo-Papua. We used an anchored hybrid enrichment approach, with near complete taxon sampling, to extract mitochondrial genomes and 376 nuclear loci to resolve and date their phylogenetic history. Biogeographic reconstruction demonstrates that they originated in Asia around 38-45 Ma and then invaded Australo-Papua around 23 Ma. Australo-Papuan pythons display a sizeable expansion in morphological space, with shifts towards numerous new adaptive optima in head and body shape, coupled with the evolution of new micro-habitat preferences. We provide an updated taxonomy of pythons and our study also demonstrates how ecological opportunity following colonization of novel environments can promote morphological diversification in a formerly ecomorphologically conservative group. [Adaptive radiation; anchored hybrid enrichment; biogeography; morphometrics; snakes.].

Interrogating Genomic-Scale Data for Squamata (Lizards, Snakes, and Amphisbaenians) Shows no Support for Key Traditional Morphological Relationships.

Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups. For one of the most diverse and species-rich groups, the squamate reptiles (lizards, snakes, and amphisbaenians), an inverse correlation between the number of taxa and loci sampled still persists across all publications using DNA sequence data and reaching a consensus on the relationships among them has been highly problematic. In this study, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome-scale data. Importantly, we address genomic support for the traditional taxonomic groupings Scleroglossa and Macrostomata using novel machine-learning techniques. We interrogate genes using various metrics inherent to these loci, including parsimony-informative sites (PIS), phylogenetic informativeness, length, gaps, number of substitutions, and site concordance to understand why certain loci fail to find previously well-supported molecular clades and how they fail to support species-tree estimates. We show that both incomplete lineage sorting and poor gene-tree estimation (due to a few undesirable gene properties, such as an insufficient number of PIS), may account for most gene and species-tree discordance. We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata. We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; among the three toxicoferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).

Rain forest shifts through time and riverine barriers shaped the diversification of South American terrestrial pit vipers (Bothrops jararacussu species group)

Aim To investigate (a) historical biogeographical connections and species interchange among rain forest habitats and (b) the role of riverine barriers on population divergence and speciation in the Neotropical region. Location Amazonia and Atlantic Forest in South America. Taxon Bothrops jararacussu species group (Serpentes: Viperidae). Methods We inferred phylogenetic relationships within Bothrops with an emphasis on the jararacussu species group under a Bayesian framework based on six molecular loci. We also used genetic coalescent simulations and approximate Bayesian computation to infer historical demography within the jararacussu group based on tests of alternative scenarios. Results We found the jararacussu species group to be monophyletic. The Atlantic Forest species B. pirajai and B. muriciensis were inferred nested within this group, closely related to B. jararacussu, confirming that Atlantic Forest species form a clade. The historical demographic analyses support vicariant separation between populations of B. brazili north and south of the Amazon River during the Miocene–Pliocene border, as well as colonization of the Atlantic Forest by a northern Amazonian ancestor in the Pleistocene. Main Conclusion The evolutionary history of the jararacussu species group sheds light on the dynamism of Neotropical rain forests over time, with at least one event of forest expansion leading to faunal interchange between Amazonian and Atlantic forests in the Pleistocene. Moreover, tests of alternative demographic scenarios suggest that the populations of B. brazili from north and south of the Amazon River originated from a vicariant event during the Miocene–Pliocene border, in agreement with the proposed age of establishment of the modern Amazon River drainage. Our results also have taxonomic implications for these medically important venomous snakes, supporting unrecognized diversity at the species level.