Snake Families Research Articles

Behavioral Plasticity and the Origins of Novelty: The Evolution of the Rattlesnake Rattle.

Environmentally induced behavior (behavioral plasticity) has long been hypothesized to promote the origins of novel morphological traits, but this idea remains controversial. One context in which this hypothesis can be evaluated is animal communication, where behavior and morphology are often linked. Here, we examined the evolution of one of nature's most spectacular communication signals: the rattlesnake rattle. We specifically evaluated whether rattlesnake rattling behavior-and, hence, the rattle-originated from a simple behavior: vibrating the tail when threatened. By reconstructing the ancestral state of defensive tail vibration, we show that this behavior is nearly ubiquitous in the Viperidae (the family that includes rattlesnakes) and widespread in the Colubridae (the largest snake family, nearly all of which are nonvenomous), suggesting a shared origin for the behavior between these families. After measuring tail vibration in 56 species of Viperidae and Colubridae, we show that the more closely related a species was to rattlesnakes, the more similar it was to rattlesnakes in duration and rate of tail vibration. Thus, the rattlesnake rattle might have evolved via elaboration of a simple behavior. These data thereby support the long-standing hypothesis that behavioral plasticity often precedes-and possibly instigates-the evolution of morphological novelty.

Trends in the Evolution of Snake Toxins Underscored by an Integrative Omics Approach to Profile the Venom of the Colubrid Phalotris mertensi.

Only few studies on snake venoms were dedicated to deeply characterize the toxin secretion of animals from the Colubridae family, despite the fact that they represent the majority of snake diversity. As a consequence, some evolutionary trends observed in venom proteins that underpinned the evolutionary histories of snake toxins were based on data from a minor parcel of the clade. Here, we investigated the proteins of the totally unknown venom from Phalotris mertensi (Dipsadinae subfamily), in order to obtain a detailed profile of its toxins and to appreciate evolutionary tendencies occurring in colubrid venoms. By means of integrated omics and functional approaches, including RNAseq, Sanger sequencing, high-resolution proteomics, recombinant protein production, and enzymatic tests, we verified an active toxic secretion containing up to 21 types of proteins. A high content of Kunitz-type proteins and C-type lectins were observed, although several enzymatic components such as metalloproteinases and an L-amino acid oxidase were also present in the venom. Interestingly, an arguable venom component of other species was demonstrated as a true venom protein and named svLIPA (snake venom acid lipase). This finding indicates the importance of checking the actual protein occurrence across species before rejecting genes suggested to code for toxins, which are relevant for the discussion about the early evolution of reptile venoms. Moreover, trends in the evolution of some toxin classes, such as simplification of metalloproteinases and rearrangements of Kunitz and Wap domains, parallel similar phenomena observed in other venomous snake families and provide a broader picture of toxin evolution.

Full-Length Venom Protein cDNA Sequences from Venom-Derived mRNA: Exploring Compositional Variation and Adaptive Multigene Evolution.

Envenomation of humans by snakes is a complex and continuously evolving medical emergency, and treatment is made that much more difficult by the diverse biochemical composition of many venoms. Venomous snakes and their venoms also provide models for the study of molecular evolutionary processes leading to adaptation and genotype-phenotype relationships. To compare venom complexity and protein sequences, venom gland transcriptomes are assembled, which usually requires the sacrifice of snakes for tissue. However, toxin transcripts are also present in venoms, offering the possibility of obtaining cDNA sequences directly from venom. This study provides evidence that unknown full-length venom protein transcripts can be obtained from the venoms of multiple species from all major venomous snake families. These unknown venom protein cDNAs are obtained by the use of primers designed from conserved signal peptide sequences within each venom protein superfamily. This technique was used to assemble a partial venom gland transcriptome for the Middle American Rattlesnake (Crotalus simus tzabcan) by amplifying sequences for phospholipases A2, serine proteases, C-lectins, and metalloproteinases from within venom. Phospholipase A2 sequences were also recovered from the venoms of several rattlesnakes and an elapid snake (Pseudechis porphyriacus), and three-finger toxin sequences were recovered from multiple rear-fanged snake species, demonstrating that the three major clades of advanced snakes (Elapidae, Viperidae, Colubridae) have stable mRNA present in their venoms. These cDNA sequences from venom were then used to explore potential activities derived from protein sequence similarities and evolutionary histories within these large multigene superfamilies. Venom-derived sequences can also be used to aid in characterizing venoms that lack proteomic profiles and identify sequence characteristics indicating specific envenomation profiles. This approach, requiring only venom, provides access to cDNA sequences in the absence of living specimens, even from commercial venom sources, to evaluate important regional differences in venom composition and to study snake venom protein evolution.

Venomic Analysis of the Poorly Studied Desert Coral Snake, Micrurus tschudii tschudii, Supports the 3FTx/PLA₂ Dichotomy across Micrurus Venoms.

The venom proteome of the poorly studied desert coral snake Micrurus tschudii tschudii was unveiled using a venomic approach, which identified ≥38 proteins belonging to only four snake venom protein families. The three-finger toxins (3FTxs) constitute, both in number of isoforms (~30) and total abundance (93.6% of the venom proteome), the major protein family of the desert coral snake venom. Phospholipases A2 (PLA2s; seven isoforms, 4.1% of the venom proteome), 1–3 Kunitz-type proteins (1.6%), and 1–2 l-amino acid oxidases (LAO, 0.7%) complete the toxin arsenal of M. t. tschudii. Our results add to the growing evidence that the occurrence of two divergent venom phenotypes, i.e., 3FTx- and PLA2-predominant venom proteomes, may constitute a general trend across the cladogenesis of Micrurus. The occurrence of a similar pattern of venom phenotypic variability among true sea snake (Hydrophiinae) venoms suggests that the 3FTx/PLA2 dichotomy may be widely distributed among Elapidae venoms.

Phylogenomic analyses reveal novel relationships among snake families

Snakes are a diverse and important group of vertebrates. However, relationships among the major groups of snakes have remained highly uncertain, with recent studies hypothesizing very different (and typically weakly supported) relationships. Here, we address family-level snake relationships with new phylogenomic data from 3776 nuclear loci from ultraconserved elements (1.40million aligned base pairs, 52% missing data overall) sampled from 29 snake species that together represent almost all families, a dataset ∼100 times larger than used in previous studies. We found relatively strong support from species-tree analyses (NJst) for most relationships, including three largely novel clades: (1) a clade uniting the boas, pythons and their relatives, (2) a clade placing cylindrophiids and uropeltids with this clade, and (3) a clade uniting bolyeriids (Round Island boas) with pythonids and their relatives (xenopeltids and loxocemids). Relationships among families of advanced snakes (caenophidians) were also strongly supported. The results show the potential for phylogenomic analyses to resolve difficult groups, but also show a surprising sensitivity of the analyses to the inclusion or exclusion of outgroups.

A Novel Anti-tumor Protein from Calloselasma Rhodostoma Venom in Vietnam

Aim: Vietnam is a tropical and agricultural country. Annually, there are 30,000 cases of snake bite. Two venomous snake families cause the big medical problem. In this, Calloselasma Rhodostoma (CR) is the most dangerous snake. Therefore, since 2001, the scientific research collaborations between Vietnam (VN) and University of Southern California (USC) were established. Since 2014 this project has been approved by VN government. The aims of the 1st project are to establish the technological process for purification of dsintegrin from CR venom of VN (CRd.VN), to determine the molecular weight, structure and its biological antitumor activities. Methods: The process of collection, lyophilisation of CR venom from VN. Protein concentration of CR venom was determined by BCA assay. High Performance Liquid Chromatography (HPLC), SDS-PAGE, Mass spectrometry (MS) analysis and sequencing by tryptic digestion were used for purification of CRd.VN and its molecular weight (MW) and structure. Standard cell biology methods were employed to characterize CRd’s abilities (in vitro) to inhibit platelet aggregation, adhesion, migration and invasion of tumor cells. Its anti-cancer activity in a breast cancer (BC) murine model (in vivo) was tested. Results: Peak 7 of HPLC (CRd.VN), showed a single ~10 kDa band on SDS-PAGE gel. CRd.VN’s MW, structure and the sequence are 7.33 kDa, a monomer containing 68 amino acids with an RGD motif (position 49-51) and 6 disulfide bonds. The anticancer activities of CRd.VN are very strong. Conclusion: We have shown that CRd.VN is a possible anti-tumor agent with clinical potential. However, further research is required on CRd recombinant production, preliminary pharmacokinetics/ toxicology properties and antitumor activities.

Evolutionary stability of sex chromosomes in snakes.

Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms.

Snake venom galactoside-binding lectins: a structural and functional overview.

Snake venom galactoside-binding lectins (SVgalLs) comprise a class of toxins capable of recognizing and interacting with terminal galactoside residues of glycans. In the past 35 years, since the first report on the purification of thrombolectin from Bothrops atrox snake venom, several SVgalLs from Viperidae and Elapidae snake families have been described, as has progressive improvement in the investigation of structural/functional aspects of these lectins. Moreover, the advances of techniques applied in protein-carbohydrate recognition have provided important approaches in order to screen for possible biological targets. The present review describes the efforts over the past 35 years to elucidate SVgalLs, highlighting their structure and carbohydrate recognition function involved in envenomation pathophysiology and potential biomedical applications.

Disintegrins from snake venoms and their applications in cancer research and therapy.

Integrins regulate diverse functions in cancer pathology and in tumor cell development and contribute to important processes such as cell shape, survival, proliferation, transcription, angiogenesis, migration, and invasion. A number of snake venom proteins have the ability to interact with integrins. Among these are the disintegrins, a family of small, non-enzymatic, and cysteine-rich proteins found in the venom of numerous snake families. The venom proteins may have a potential role in terms of novel therapeutic leads for cancer treatment. Disintegrin can target specific integrins and as such it is conceivable that they could interfere in important processes involved in carcinogenesis, tumor growth, invasion and migration. Herein we present a survey of studies involving the use of snake venom disintegrins for cancer detection and treatment. The aim of this review is to highlight the relationship of integrins with cancer and to present examples as to how certain disintegrins can detect and affect biological processes related to cancer. This in turn will illustrate the great potential of these molecules for cancer research. Furthermore, we also outline several new approaches being created to address problems commonly associated with the clinical application of peptide-based drugs such as instability, immunogenicity, and availability.

The evolution of tail length in snakes associated with different gravitational environments

SummaryGravity imposes potentially important constraints on blood circulation in tall or elongate animals during upright posture or climbing. Upright postures create vertical gradients of gravitational (=hydrostatic) pressures within circulatory vessels. In terrestrial animals, this pressure potentially induces blood pooling and oedema in dependent (inferior) tissues and, secondarily, decreases blood volume reaching the head and vital organs. Arboreal snakes exhibit a suite of adaptations for countering the effects of gravity on blood circulation, including relatively non‐compliant tissue compartments in the tail. However, patterns of tail length related to arboreal habitats and gravity have not been previously studied. Here, we test the hypothesis that arboreal snakes have relatively longer tails than non‐climbing species, and we interpret the results within the context of adaptation to gravity stress.Length data were obtained for 226 snake species, 139 genera and 15 snake families assigned to three broad gravitational habitat categories (G‐habitats: stenotopically arboreal, eurytopically arboreal/terrestrial and non‐scansorial). We constructed a composite phylogenetic tree and quantified the relationships between snake morphology and G‐habitat using conventional regression analysis of species data and regressions of phylogenetically independent contrasts.Mean relative tail length (RTL) increased and mean relative snout‐vent length decreased with increasing arboreality among the three G‐habitats. However, mean total body length (TL) was not different between the two arboreal G‐habitats.Snakes with longerRTLs have a higher percentage of elongate blood vessels contained within the relatively non‐compliant integument of the tail, which mitigates postural blood pooling experienced during climbing.TLin adult female arboreal snakes is hypothesized to be an evolutionary trade‐off between demands for a longer tail to enhance cardiovascular performance and the length of body cavity to provide space for young.Our results complement previous studies correlatingRTLwith arboreal habitat use, in addition to physiological experiments quantifying the effects of gravity on blood flow in snakes. These results provide evidence that longRTLs of arboreal snakes function, at least in part, as an adaptive response to cardiovascular stresses on blood circulation imposed by gravity. Selection on tail length related to other factors seems less likely, but is in need of further investigation.

Comparative morphology of the snake spectacle using light and transmission electron microscopy.

To determine the interspecific variation in the morphology of the snake spectacle. About 43 snakes of 14 different species, belonging to three different families: Boidae, Colubridae, and Pythonidae. The spectacles were examined by light and transmission electron microscopy. The thickness of the stromal layer was measured and the location of the blood vessels was noted. The shape of the transition zone located at the rim of the spectacle and the presence of pigment herein were also recorded. The spectacles of all species examined consisted of three layers. The outer epithelium was made of basal cells with overlaying keratin layers, the stroma comprised layers of organized collagen fibrils, and the inner epithelium was a layer of squamous cells with microvilli. Blood vessels were found in the stroma of all spectacles: in boas and pythons in the middle layers of the stroma and in colubrids adjacent to the inner epithelium. Boas and pythons were endowed with the thickest stromal layers (81-132μm) compared to colubrids (9-95μm). Boas and pythons had a convex transition zone, while the transition zone of the colubrids exhibited a steady increase in spectacle thickness toward the hinge region. The transition zone contained pigment in boas and pythons. The overall morphology of the spectacle was similar among the major families of snakes. However, the location of blood vessels and appearance of transition zone differed, as did the overall thickness of the spectacle.

Why the honey badger don't care: Convergent evolution of venom-targeted nicotinic acetylcholine receptors in mammals that survive venomous snake bites.

Honey badgers (Mellivora capensis) prey upon and survive bites from venomous snakes (Family: Elapidae), but the molecular basis of their venom resistance is unknown. The muscular nicotinic cholinergic receptor (nAChR), targeted by snake α-neurotoxins, has evolved in some venom-resistant mammals to no longer bind these toxins. Through phylogenetic analysis of mammalian nAChR sequences, we show that honey badgers, hedgehogs, and pigs have independently acquired functionally equivalent amino acid replacements in the toxin-binding site of this receptor. These convergent amino acid changes impede toxin binding by introducing a positively charged amino acid in place of an uncharged aromatic residue. In venom-resistant mongooses, different replacements at these same sites are glycosylated, which is thought to disrupt binding through steric effects. Thus, it appears that resistance to snake venom α-neurotoxin has evolved at least four times among mammals through two distinct biochemical mechanisms operating at the same sites on the same receptor.

Species Diversity of Snakes in Pachmarhi Biosphere Reserve

Madhya Pradesh (MP), the central Indian state is well-renowned for reptile fauna. In particular, Pachmarhi Biosphere Reserve (PBR) regions (Districts Hoshangabad, Betul and Chindwara) of MP comprises a vast range of reptiles, especially herpetofauna yet unexplored from the conservation point of view. Earlier inventory herpetofaunal study conducted in 2005 at MP and Chhattisgarh (CG) reported 6 snake families included 39 species. After this preliminary report, no literature existing regarding snake diversity of this region. This situation incited us to update the snake diversity of PBR regions. From 2010 to 2012, we conducted a detailed field study and recorded 31 species of 6 snake families (Boidae, Colubridae, Elapidae, Typhlopidea, Uropeltidae, and Viperidae) in Hoshanagbad District (Satpura Tiger Reserve) and PBR regions. Besides, we found the occurrence of Boiga forsteni and Coelognatus helena monticollaris (Colubridae), which was not previously reported in PBR region. Among the recorded, 9 species were Lower Risk – least concerned (LR-lc), 20 were of Lower Risk – near threatened (LR-nt), 1 is Endangered (EN) and 1 is vulnerable (VU) according to International Union for Conservation of Nature (IUCN) status. Hence, there is an urgent need for strategies to conserve these rare and threatened snakes in PBR.

Inhibition of nicotinic acetylcholine receptors, a novel facet in the pleiotropic activities of snake venom phospholipases A2.

Phospholipases A2 represent the most abundant family of snake venom proteins. They manifest an array of biological activities, which is constantly expanding. We have recently shown that a protein bitanarin, isolated from the venom of the puff adder Bitis arietans and possessing high phospholipolytic activity, interacts with different types of nicotinic acetylcholine receptors and with the acetylcholine-binding protein. To check if this property is characteristic to all venom phospholipases A2, we have studied the capability of these enzymes from other snakes to block the responses of Lymnaea stagnalis neurons to acetylcholine or cytisine and to inhibit α-bungarotoxin binding to nicotinic acetylcholine receptors and acetylcholine-binding proteins. Here we present the evidence that phospholipases A2 from venoms of vipers Vipera ursinii and V. nikolskii, cobra Naja kaouthia, and krait Bungarus fasciatus from different snake families suppress the acetylcholine- or cytisine-elicited currents in L. stagnalis neurons and compete with α-bungarotoxin for binding to muscle- and neuronal α7-types of nicotinic acetylcholine receptor, as well as to acetylcholine-binding proteins. As the phospholipase A2 content in venoms is quite high, under some conditions the activity found may contribute to the deleterious venom effects. The results obtained suggest that the ability to interact with nicotinic acetylcholine receptors may be a general property of snake venom phospholipases A2, which add a new target to the numerous activities of these enzymes.

Evaluation of cytotoxic activities of snake venoms toward breast (MCF-7) and skin cancer (A-375) cell lines.

Snake venoms are mixtures of bioactive proteins and peptides that exhibit diverse biochemical activities. This wide array of pharmacologies associated with snake venoms has made them attractive sources for research into potentially novel therapeutics, and several venom-derived drugs are now in use. In the current study we performed a broad screen of a variety of venoms (61 taxa) from the major venomous snake families (Viperidae, Elapidae and "Colubridae") in order to examine cytotoxic effects toward MCF-7 breast cancer cells and A-375 melanoma cells. MTT cell viability assays of cancer cells incubated with crude venoms revealed that most venoms showed significant cytotoxicity. We further investigated venom from the Red-bellied Blacksnake (Pseudechis porphyriacus); venom was fractionated by ion exchange fast protein liquid chromatography and several cytotoxic components were isolated. SDS-PAGE and MALDI-TOF mass spectrometry were used to identify the compounds in this venom responsible for the cytotoxic effects. In general, viper venoms were potently cytotoxic, with MCF-7 cells showing greater sensitivity, while elapid and colubrid venoms were much less toxic; notable exceptions included the elapid genera Micrurus, Naja and Pseudechis, which were quite cytotoxic to both cell lines. However, venoms with the most potent cytotoxicity were often not those with low mouse LD50s, including some dangerously venomous viperids and Australian elapids. This study confirmed that many venoms contain cytotoxic compounds, including catalytic PLA2s, and several venoms also showed significant differential toxicity toward the two cancer cell lines. Our results indicate that several previously uncharacterized venoms could contain promising lead compounds for drug development.

Expression of venom gene homologs in diverse python tissues suggests a new model for the evolution of snake venom.

Snake venom gene evolution has been studied intensively over the past several decades, yet most previous studies have lacked the context of complete snake genomes and the full context of gene expression across diverse snake tissues. We took a novel approach to studying snake venom evolution by leveraging the complete genome of the Burmese python, including information from tissue-specific patterns of gene expression. We identified the orthologs of snake venom genes in the python genome, and conducted detailed analysis of gene expression of these venom homologs to identify patterns that differ between snake venom gene families and all other genes. We found that venom gene homologs in the python are expressed in many different tissues outside of oral glands, which illustrates the pitfalls of using transcriptomic data alone to define "venom toxins." We hypothesize that the python may represent an ancestral state prior to major venom development, which is supported by our finding that the expansion of venom gene families is largely restricted to highly venomous caenophidian snakes. Therefore, the python provides insight into biases in which genes were recruited for snake venom systems. Python venom homologs are generally expressed at lower levels, have higher variance among tissues, and are expressed in fewer organs compared with all other python genes. We propose a model for the evolution of snake venoms in which venom genes are recruited preferentially from genes with particular expression profile characteristics, which facilitate a nearly neutral transition toward specialized venom system expression.

Immunogold labeling shows that glycine-cysteine-rich beta-proteins are deposited in the Oberhäutchen layer of snake epidermis in preparation to shedding.

Shedding in snakes is cyclical and derives from the differentiation of an intraepidermal shedding complex made of two different layers, termed clear and Oberhäutchen that determine the separation between the outer from the inner epidermal generation that produces a molt. The present comparative immunocytochemical study on the epidermis and molts of different species of snakes shows that a glycine-cysteine-rich corneous beta-protein in a snake is prevalently accumulated in cells of the Oberhäutchen layer and decreases in those of the beta-layer. The protein is variably distributed in the mature beta-layer of species representing some snake families when the beta-layer merges with the Oberhäutchen but disappears in alpha-layers. Therefore, this protein represents an early marker of the transition between the outer and the inner epidermal generations in the epidermis of snakes in general. It is hypothesized that specific gene activation for glycine-cysteine-rich corneous beta-proteins occurs during the passage from the clear layer of the outer epidermal generation to the Oberhäutchen layer of the replacing inner epidermal generation. It is suggested that in the epidermis of most species glycine-cysteine-rich corneous beta-proteins form part of the dense corneous material that rapidly accumulates in the differentiating Oberhäutchen cells but decreases in the following beta-layer of the inner epidermal generation destined to be separated from the previous outer generation in the process of shedding. The regulation of the synthesis of these and other proteins is, therefore, crucial in timing the different stages of the shedding cycle in lepidosaurian reptiles.

Phylogeny of courtship and male-male combat behavior in snakes.

BackgroundBehaviors involved in courtship and male-male combat have been recorded in a taxonomically broad sample (76 species in five families) of snakes in the clade Boidae + Colubroidea, but before now no one has attempted to find phylogenetic patterns in such behaviors. Here, we present a study of phylogenetic patterns in such behaviors in snakes.Methodology/Principal FindingsFrom the literature on courtship and male-male combat in snakes we chose 33 behaviors to analyze. We plotted the 33 behaviors onto a phylogenetic tree to determine whether phylogenetic patterns were discernible. We found that phylogenetic patterns are discernible for some behaviors but not for others. For behaviors with discernible phylogenetic patterns, we used the fossil record to determine minimum ages for the addition of each behavior to the courtship and combat behavioral repertoire of each snake clade.Conclusions/SignificanceThe phylogenetic patterns of behavior reveal that male-male combat in the Late Cretaceous common ancestors of Boidae and Colubridae involved combatants raising the head and neck and attempting to topple each other. Poking with spurs was added in Boidae. In Lampropeltini the toppling behavior was replaced by coiling without neck-raising, and body-bridging was added. Phylogenetic patterns reveal that courtship ancestrally involved rubbing with spurs in Boidae. In Colubroidea, courtship ancestrally involved chin-rubbing and head- or body-jerking. Various colubroid clades subsequently added other behaviors, e.g. moving undulations in Natricinae and Lampropeltini, coital neck biting in the Eurasian ratsnake clade, and tail quivering in Pantherophis. The appearance of each group in the fossil record provides a minimum age of the addition of each behavior to combat and courtship repertoires. Although many gaps in the story of the evolution of courtship and combat in snakes remain, this study is an important first step in the reconstruction of the evolution of these behaviors in snakes.

A Checklist and Key to the Homalopsid Snakes (Reptilia, Squamata, Serpentes), with the Description of New Genera

Abstract The colubroid snake family Homalopsidae contained 10 genera and 34 species of rear-fanged semi-aquatic and aquatic snakes in 1970 with the publication of Gyi's monograph. In 2007 Murphy had updated Gyi's work and the family held the same 10 genera with 37 species plus two genera with uncertain status (Anoplohydrus, Brachyorrhos). Molecular studies published in the first decade of the 21st century demonstrated that while the Homalopsidae is monophyletic, the species-rich genus Enhydris is polyphyletic. Molecular analysis also found Brachyorrhos to be the most basal member of the clade, confirming an earlier hypothesis that it was a fangless homalopsid. Subsequently, two other fangless genera of homalopsids were discovered. We revalidate the genera: Homalophis Peters, Hypsiscopus Fitzinger, Miralia Reuss, Phytolopsis Gray, and Raclitia Gray. Also, we describe five new genera for species lacking available names: Gyiophis, Kualatahan, Mintonophis, Sumatranus, and Subsessor. The new arrangement for ho...

A framework for assessing the vulnerability of species to climate change: a case study of the Australian elapid snakes

Frameworks that provide a system for assessing species according to their vulnerability to climate change can offer considerable guidance to conservation managers who need to allocate limited resources among a large number of taxa. To date, climate change vulnerability assessments have largely been based on projected changes in range size derived from the output of species distribution models (SDMs). A criticism of risk assessments based solely on these models is that information on species ecological and life history traits is lacking. Accordingly, we developed a points-based framework for assessing species vulnerability to climate change that considered species traits together with the projections of SDMs. Applying this method to the Australian elapid snakes (family Elapidae), we determined which species may be particularly susceptible in the future and assessed broad-scale biogeographic patterns in species vulnerability. By offering a more comprehensive and rigorous method for assessing vulnerability than those based solely on SDMs, this framework provides greater justification for resource allocation, and can help guide decisions regarding the most appropriate adaptation strategies.