Cryptic diversity and phylogeography of the Rhabdophis nuchalis group (Squamata: Colubridae)

Previous studies, have found that the rapid uplift of the Tibetan plateau accelerated the diversification of species. However, there are few relevant biogeographic data for the Colubridae in this region. We conducted a comprehensive study of the Rhabdophis nuchalis Group, which presently contains four nominal species, R. nuchalis, R. pentasupralabialis, R. leonardi, and R. chiwen. Building upon previous studies with specimens we have recently examined, greater interspecific and intraspecific diversity has been revealed. Here we address three questions: (1) Do the intraspecific differences represent only geographic variation within lineages, or are there cryptic species? (2) What are the interspecific relationships among members of the R. nuchalis Group? (3) What has been the biogeographic history of this species group? To resolve these questions we used four mitochondrial gene sequences and one nuclear sequence to investigate the molecular phylogenetic and geographic relationships among populations. Our molecular analysis reveals cryptic species diversity within the R. nuchalis Group, and seven clades were identified in the analysis. Ancestral area estimation suggests that the R. nuchalis Group originated in the Hengduan Mountains approximately 6.24 Mya and expanded its range northward to the Qinling-Daba Mountains. The Sichuan Basin appears to have been a barrier to migration. Species divergence seems to have been related to the rapid uplift of the Qinghai-Tibet Plateau.

Taxonomic revision of the genus Xenopholis Peters, 1869 (Serpentes: Dipsadidae): Integrating morphology with ecological niche

A reliable identification and delimitation of species is an essential pre-requisite for many fields of science and conservation. The Neotropical herpetofauna is the world's most diverse, including many taxa of uncertain or debated taxonomy. Here we tackle one such species complex, by evaluating the taxonomic status of species currently allocated in the snake genus Xenopholis (X. scalaris, X. undulatus, and X. werdingorum). We base our conclusions on concordance between quantitative (meristic and morphometric) and qualitative (color pattern, hemipenes and skull features) analyses of morphological characters, in combination with ecological niche modeling. We recognize all three taxa as valid species and improve their respective diagnosis, including new data on color in life, pholidosis, bony morphology, and male genitalia. We find low overlap among the niches of each species, corroborating the independent source of phenotypic evidence. Even though all three species occur in the leaf litter of distinct forested habitats, Xenopholis undulatus is found in the elevated areas of the Brazilian Shield (Caatinga, Cerrado and Chaco), whereas X. scalaris occurs in the Amazon and Atlantic rainforests, and X. werdingorum in the Chiquitanos forest and Pantanal wetlands. We discuss the disjunct distribution between Amazonian and Atlantic Forest snake species in the light of available natural history and ecological aspects. This study shows the advantages of combining multiple data sources for reliable identification and circumscription of ecologically similar species.

Philodryas (Serpentes: Dipsadidae) Envenomation, a Neglected Issue in Chile

Snakebite envenomation is considered a neglected tropical disease, although it also occurs outside the tropics. In this work, we analyzed the literature on Philodryas species in Chile (Philodryaschamissonis, P.simonsii, and P.tachymenoides) from 1834 to 2019, searching for epidemiological, clinical, and molecular aspects of envenomation. Ninety-one percent of the studies found regarded taxonomy, ecology, and natural history, suggesting that snakebites and venom toxins are a neglected issue in Chile. All snakebite cases reported and toxicological studies concerned the species Philodryaschamissonis. Using 185 distributional records from the literature and museum collections for this species, we show for the first time that the reported snakebite cases correlate with human population density, occurring in the Valparaiso and Metropolitan regions in Central Chile. The reduced number of snakebite cases, which were previously considered as having a low incidence in Chile, may be a consequence of under-reported cases, probably due to the inadequate publication or scarce research on this issue. Absence of information about official pharmacological treatment, post-envenoming sequels, clinical management of particular patient groups (e.g., with non-communicable diseases, pregnant women, and the elderly) was also detected. In conclusion, despite having over 185 years of literature on Chilean snakes, knowledge on the envenomation of Philodryas genus remains scarce, seriously affecting adequate medical handling during an ophidic accident. This review highlights the need to develop deep research in this area and urgent improvements to the management of this disease in Chile.

Discovery of a deeply divergent new lineage of vine snake (Colubridae: Ahaetuliinae: Proahaetulla gen. nov.) from the southern Western Ghats of Peninsular India with a revised key for Ahaetuliinae

The Western Ghats are well known as a biodiversity hotspot, but the full extent of its snake diversity is yet to be uncovered. Here, we describe a new genus and species of vine snake Proahaetulla antiqua gen. et sp. nov., from the Agasthyamalai hills in the southern Western Ghats. It was found to be a member of the Ahaetuliinae clade, which currently comprises the arboreal snake genera Ahaetulla, Dryophiops, Dendrelaphis and Chrysopelea, distributed in South and Southeast Asia. Proahaetulla shows a sister relationship with all currently known taxa belonging to the genus Ahaetulla, and shares ancestry with Dryophiops. In addition to its phylogenetic position and significant genetic divergence, this new taxon is also different in morphology from members of Ahaetuliinae in a combination of characters, having 12-13 partially serrated keels on the dorsal scale rows, 20 maxillary teeth and 3 postocular scales. Divergence dating reveals that the new genus is ancient, dating back to the Mid-Oligocene, and is one of the oldest persisting monotypic lineages of snakes in the Western Ghats. This discovery adds to the growing list of ancient lineages endemic to the Agasthyamalai hills and underscores the biogeographic significance of this isolated massif in the southern Western Ghats.

Independent Demographic Responses to Climate Change among Temperate and Tropical Milksnakes (Colubridae: Genus Lampropeltis)

The effects of Late Quaternary climate change have been examined for many temperate New World taxa, but the impact of Pleistocene glacial cycles on Neotropical taxa is less well understood, specifically with respect to changes in population demography. Here, we examine historical demographic trends for six species of milksnake with representatives in both the temperate and tropical Americas to determine if species share responses to climate change as a taxon or by area (i.e., temperate versus tropical environments). Using a multilocus dataset, we test for the demographic signature of population expansion and decline using non-genealogical summary statistics, as well as coalescent-based methods. In addition, we determine whether range sizes are correlated with effective population sizes for milksnakes. Results indicate that there are no identifiable trends with respect to demographic response based on location, and that species responded to changing climates independently, with tropical taxa showing greater instability. There is also no correlation between range size and effective population size, with the largest population size belonging to the species with the smallest geographic distribution. Our study highlights the importance of not generalizing the demographic histories of taxa by region and further illustrates that the New World tropics may not have been a stable refuge during the Pleistocene.

New Record of Lycodon liuchengchaoi in Anhui

One juvenile and one adult female wolf snake (Colubridae: Lycodon) were sampled at Yixian and Fuxi, Huangshan, Anhui, China in the summer of 2011 and 2012, respectively. The two specimens were identified as Lycodon liuchengchaoi based on external morphology and molecular data. This is a new reptile record in Anhui Province. In our laboratory, four eggs were laid and three neonates were hatched successfully. This is the first record of the laying and incubation of L. liuchengchaoi eggs. The five specimens were deposited at the Museum of Huangshan University (HUM20140001) and Guangdong Entomological Institute (HB-lcfsp12613, HB-lcfsp-ch1~3).

Phylogeny of courtship and male-male combat behavior in snakes

Background

Behaviors 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 Findings

From 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/Significance

The 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.

Fuzzy boundaries: color and gene flow patterns among parapatric lineages of the western shovel-nosed snake and taxonomic implication

Accurate delineation of lineage diversity is increasingly important, as species distributions are becoming more reduced and threatened. During the last century, the subspecies category was often used to denote phenotypic variation within a species range and to provide a framework for understanding lineage differentiation, often considered incipient speciation. While this category has largely fallen into disuse, previously recognized subspecies often serve as important units for conservation policy and management when other information is lacking. In this study, we evaluated phenotypic subspecies hypotheses within shovel-nosed snakes on the basis of genetic data and considered how evolutionary processes such as gene flow influenced possible incongruence between phenotypic and genetic patterns. We used both traditional phylogenetic and Bayesian clustering analyses to infer range-wide genetic structure and spatially explicit analyses to detect possible boundary locations of lineage contact. Multilocus analyses supported three historically isolated groups with low to moderate levels of contemporary gene exchange. Genetic data did not support phenotypic subspecies as exclusive groups, and we detected patterns of discordance in areas where three subspecies are presumed to be in contact. Based on genetic and phenotypic evidence, we suggested that species-level diversity is underestimated in this group and we proposed that two species be recognized, Chionactis occipitalis and C. annulata. In addition, we recommend retention of two subspecific designations within C. annulata (C. a. annulata and C. a. klauberi) that reflect regional shifts in both genetic and phenotypic variation within the species. Our results highlight the difficultly in validating taxonomic boundaries within lineages that are evolving under a time-dependent, continuous process.

Consuming viscous prey: a novel protein-secreting delivery system in neotropical snail-eating snakes

BACKGROUND

Efficient venom delivery systems are known to occur only in varanoid lizards and advanced colubroidean snakes among squamate reptiles. Although components of these venomous systems might have been present in a common ancestor, the two lineages independently evolved strikingly different venom gland systems. In snakes, venom is produced exclusively by serous glands in the upper jaw. Within the colubroidean radiation, lower jaw seromucous infralabial glands are known only in two distinct lineages-the basal pareatids and the more advanced Neotropical dipsadines known as "goo-eating snakes". Goo-eaters are a highly diversified, ecologically specialized clade that feeds exclusively on invertebrates (e.g., gastropod molluscs and annelids). Their evolutionary success has been attributed to their peculiar feeding strategies, which remain surprisingly poorly understood. More specifically, it has long been thought that the more derived Dipsadini genera Dipsas and Sibynomorphus use glandular toxins secreted by their infralabial glands to extract snails from their shells.

RESULTS

Here, we report the presence in the tribe Dipsadini of a novel lower jaw protein-secreting delivery system effected by a gland that is not functionally related to adjacent teeth, but rather opens loosely on the oral epithelium near the tip of the mandible, suggesting that its secretion is not injected into the prey as a form of envenomation but rather helps control the mucus and assists in the ingestion of their highly viscous preys. A similar protein-secreting system is also present in the goo-eating genus Geophis and may share the same adaptive purpose as that hypothesized for Dipsadini. Our phylogenetic hypothesis suggests that the acquisition of a seromucous infralabial gland represents a uniquely derived trait of the goo-eating clade that evolved independently twice within the group as a functionally complex protein-secreting delivery system.

CONCLUSIONS

The acquisition by snail-eating snakes of such a complex protein-secreting system suggests that the secretion from the hypertrophied infralabial glands of goo-eating snakes may have a fundamental role in mucus control and prey transport rather than envenomation of prey. Evolution of a functional secretory system that combines a solution for mucus control and transport of viscous preys is here thought to underlie the successful radiation of goo-eating snakes.

Identification and characterization of a taxon-specific three-finger toxin from the venom of the Green Vinesnake (Oxybelis fulgidus; family Colubridae)

Snake venoms contain a variety of protein and peptide toxins, and the three-finger toxins (3FTxs) are among the best characterized family of venom proteins. The compact nature and highly conserved molecular fold of 3FTxs, together with their abundance in many venoms, has contributed to their utility in structure-function studies. Although many target the nicotinic acetylcholine receptor of vertebrate skeletal muscle, often binding with nanomolar Kds, several non-conventional 3FTxs show pronounced taxon-specific neurotoxic effects. Here we describe the purification and characterization of fulgimotoxin, a monomeric 3FTx from the venom of Oxybelis fulgidus, a neotropical rear-fanged snake. Fulgimotoxin retains the canonical 5 disulfides of the non-conventional 3FTxs and is highly neurotoxic to lizards; however, mice are unaffected, demonstrating that this toxin is taxon-specific in its effects. Analysis of structural features of fulgimotoxin and other colubrid venom 3FTxs indicate the presence of a "colubrid toxin motif" (CYTLY) and a second conserved segment (WAVK) found in Boiga and Oxybelis taxon-specific 3FTxs, both in loop II. Because specific residues in loop II conventional α-neurotoxic 3FTxs are intimately associated with receptor binding, we hypothesize that this loop, with its highly conserved substitutions, confers taxon-specific neurotoxicity. These findings underscore the importance of rear-fanged snake venoms for understanding the evolution of toxin molecules and demonstrate that even among well-characterized toxin families, novel structural and functional motifs may be found.

Lycodon and Dinodon: one genus or two? Evidence from molecular phylogenetics and morphological comparisons

Based on a molecular phylogeny and a comparison of maxillary dentition and morphology, the relationship between the genera Lycodon and Dinodon was investigated. Bayesian Inference and Maximum Likelihood analysis of two mitochondrial genes (cyt b and ND4) and two nuclear genes (c-mos and Rag1) suggested that the two genera shared a most recent common ancestor. However, Dinodon was paraphyletic and Lycodon was polyphyletic, each with respect to the other. The results from counts of maxillary teeth indicated that the diagnostic characters used by previous authors to separate Dinodon and Lycodon were not reliable. Taking the molecular and morphological evidence together, we synonymized Dinodon with Lycodon. In addition, the validity of the species L. futsingensis was confirmed to be distinctly different from the other species of Dinodon and Lycodon.

Non-front-fanged colubroid snakes: a current evidence-based analysis of medical significance

Non-front-fanged colubroid snakes (NFFC; formerly and artificially taxonomically assembled as "colubrids") comprise about 70% of extant snake species and include several taxa now known to cause lethal or life threatening envenoming in humans. Although the medical risks of bites by only a handful of species have been documented, a growing number of NFFC are implicated in medically significant bites. The majority of these snakes have oral products (Duvernoy's secretions, or venoms) with unknown biomedical properties and their potential for causing harm in humans is unknown. Increasingly, multiple NFFC species are entering the commercial snake trade posing an uncertain risk. Published case reports describing NFFC bites were assessed for evidence-based value, clinical detail and verified species identification. These data were subjected to meta-analysis and a hazard index was generated for select taxa. Cases on which we consulted or personally treated were included and subjected to the same assessment criteria. Cases involving approximately 120 species met the selection criteria, and a small subset designated Hazard Level 1 (most hazardous), contained 5 species with lethal potential. Recommended management of these cases included antivenom for 3 species, Dispholidus typus, Rhabdophis tiginis, Rhabdophis subminiatus, whereas others in this subset without commercially available antivenoms (Thelotornis spp.) were treated with plasma/erythrocyte replacement therapy and supportive care. Heparin, antifibrinolytics and/or plasmapheresis/exchange transfusion have been used in the management of some Hazard Level 1 envenomings, but evidence-based analysis positively contraindicates the use of any of these interventions. Hazard Level 2/3 species were involved in cases containing mixed quality data that implicated these taxa (e.g. Boiga irregularis, Philodryas olfersii, Malpolon monspessulanus) with bites that caused rare systemic effects. Recommended management may include use of acetylcholinesterase inhibitors (e.g. neostigmine) and wound care on a case-by-case basis. Hazard level 3 species comprised a larger group capable of producing significant local effects only, often associated with a protracted bite (eg Heterodon nasicus, Borikenophis (Alsophis) portoricensis, Platyceps (Coluber) rhodorachis). Management is restricted to wound care. Bites by Hazard level 4 species comprised the majority of surveyed taxa and these showed only minor effects of no clinical importance. This study has produced a comprehensive evidence-based listing of NFFC snakes tabulated against medical significance of bites, together with best-practice management recommendations. This analysis assumes increasing importance, as there is growing exposure to lesser-known NFFC snakes, particularly in captive collections that may uncover further species of significance in the future. Careful and accurate documentation of bites by verified species of NFFC snakes is required to increase the evidence base and establish the best medical management approach for each species.

A phylogeny of the Lampropeltis mexicana complex (Serpentes: Colubridae) based on mitochondrial DNA sequences suggests evidence for species-level polyphyly within Lampropeltis

The systematic relationships of snakes in the Lampropeltis mexicana complex (L. mexicana, L. alterna, and L. ruthveni) are poorly known despite several taxonomic studies over the last 80 years. Mitochondrial DNA sequences were used to infer the phylogeny of the L. mexicana complex. At least one representative sample from the nine currently recognized species of Lampropeltis was sequenced. Our results suggest that a deep basal split resulted in the divergence of two groups of Lampropeltis, with one group occupying the upland areas of western United States and most of western and central Mexico, and the other northeastern Mexico and the lowland areas of the southern United States. Results also revealed that the L. mexicana complex and Lampropeltis triangulum are polyphyletic, with taxa from both groups nested together in deeply divergent northern and southern clades. These results are incongruent with previous hypotheses of phylogenetic relationships based on morphology, and suggest that morphological characters shared among the various tri-colored Lampropeltis (e.g., hemipenal structure and tri-colored pattern) may be difficult to interpret phylogenetically.

A new species of Dipsas (Squamata: Colubridae) from Guyana

A new species of Dipsas is described from the Pakaraima Mountains of Guyana. The new species is characterised by 15 dorsal scale rows with the middorsal row slightly enlarged. four pairs of chinshields with the first pair elongate, elongate loreal entering orbit, one preocular, six upper labials, and head narrow anteriorly, increasing in width posteriorly. It could not be determined to which of Peters' (1960) species groups the new species belongs. The new species is known only from 1490 m elevation on Mount Ayanganna. a tepui in the Guiana Shield, where it was found in high-tepui low-canopy habitat, in bromeliads or branches. This is the first record of Dipsas as a member of the Guiana Shield high-tepui herpetofauna.

Hybridization between mtDNA-defined phylogeographic lineages of black ratsnakes (Pantherophis sp.)

Phylogeographic analyses using mitochondrial DNA (mtDNA) have revealed many examples of apparently deep historical subdivisions ('phylogroups') within many vertebrates. It remains unclear whether these phylogroups represent independently evolving, adaptively differentiated lineages or groups that show little functional differentiation and, hence, will merge on contact. Here, we use mtDNA sequence data to evaluate the phylogeographic relationships between two of the northernmost populations of black ratsnakes (Pantherophis obsoletus complex) in Ontario, Canada and previously analysed populations in the United States. We then use population-level analyses to evaluate the level of adaptive divergence between previously established mtDNA phylogroups. Phylogenetic analyses show that southern Ontario snakes have mtDNA haplotypes that fall within the Central mtDNA phylogroup, as designated by Burbrink et al. (2000). In contrast, snakes in eastern Ontario carry either Central or Eastern-specific haplotypes. Within the hybrid region, we found highly variable frequencies of mtDNA haplotypes among isolated sub-populations, no association between variation in cytonuclear (mtDNA) and nuclear (microsatellite DNA) markers, no difference in survival or reproductive success among snakes with different mtDNA haplotypes, and no effect of mate similarity in mtDNA on female clutch size. These results argue that the Eastern and Central phylogroups have merged in this region, likely due to a lack of adaptive differentiation between individuals in each lineage. Hence, in these snakes, phylogeographic structure in mtDNA is more a reflection of historical isolation rather than adaptive divergence. The observed reticulation between lineages and lack of evidence for hybrid disgenesis also bears on the classification of these lineages as distinct species.

Some aspects of the venom proteome of the Colubridae snakePhilodryas olfersiirevealed from a Duvernoy's (venom) gland transcriptome

We investigated the putative toxins of Philodryas olfersii (Colubridae), a representative of a family of snakes neglected in venom studies despite their growing medical importance. Transcriptomic data of the venom gland complemented by proteomic analysis of the gland secretion revealed the presence of major toxin classes from the Viperidae family, including serine proteases, metalloproteases, C-type lectins, Crisps, and a C-type natriuretic peptide (CNP). Interestingly, the phylogenetic analysis of the CNP precursor showed it as a linker between two related precursors found in Viperidae and Elapidae snakes. We suggest that these precursors constitute a monophyletic group derived from the vertebrate CNPs.

Influence of body size on swimming performance of four species of neonatal natricine snakes acutely exposed to a cholinesterase-inhibiting pesticide

Locomotor performance is an important fitness-related trait in reptiles because of its potential influence on prey capture and predator avoidance. Because cholinesterase-inhibiting pesticides disrupt neuromuscular signaling, reduction in performance seems to be a logical translation of this biochemical disruption to the organism level. In the present study, we compared the swimming performance of four species of natricine snakes acutely exposed to a formulation of carbaryl to determine whether neonatal body size or skin permeability influences responsiveness. Exposure to high concentrations of carbaryl (2.5-5.0 mg/L) resulted in reduced swimming performance in all four species of snakes, and species responded similarly to the pesticide once body size was accounted for allometrically. Using traditional methods in physiological ecology to estimate skin permeability (a parameter that influences the dose of contaminant absorbed), we found that water flux across the integument also scaled allometrically with body surface area and, therefore, was similar among species after controlling for this relationship. We suggest that future studies examining the effects of repeated low-dose exposure to cholinesterase inhibitors on performance parameters will be useful in assessing the ecological significance of our findings.

Relict snakes of North America and their relationships within Caenophidia, using likelihood-based Bayesian methods on mitochondrial sequences

This paper focuses on the phylogenetic relationships of eight North American caenophidian snake species (Carphophis amoena, Contia tenuis, Diadophis punctatus, Farancia abacura, Farancia erytrogramma, Heterodon nasicus, Heterodon platyrhinos, and Heterodon simus) whose phylogenetic relationships remain controversial. Past studies have referred to these "relict" North American snakes either as colubrid, or as Neotropical dipsadids and/or xenodontids. Based on mitochondrial DNA ribosomal gene sequences and a likelihood-based Bayesian analysis, our study suggests that these North American snakes are not monophyletic and are nested within a group (Dipsadoidea) that contains the Dipsadidae, Xenodontidae, and Natricidae. In addition, we use the relationships proposed here to highlight putative examples of parallel evolution of hemipenial morphology among snake clades.

Phylogeographic analysis of the cornsnake (Elaphe guttata) complex as inferred from maximum likelihood and Bayesian analyses

Most phylogeographic studies have used maximum likelihood or maximum parsimony to infer phylogeny and bootstrap analysis to evaluate support for trees. Recently, Bayesian methods using Marlov chain Monte Carlo to search tree space and simultaneously estimate tree support have become popular due to its fast search speed and ability to create a posterior distribution of parameters of interest. Here, I present a study that utilizes Bayesian methods to infer phylogenetic relationships of the cornsnake (Elaphe guttata) complex using cytochrome b sequences. Examination of the posterior probability distributions confirms the existence of three geographic lineages. Additionally, there is no support for the monophyly of the subspecies of E. guttata. Results suggest the three geographic lineages partially conform to the ranges of previously defined subspecies, although Shimodaira-Hasegawa tests suggest that subspecies-constrained trees produce significantly poorer likelihood estimates than the most likely trees reflecting the evolution of three geographic assemblages. Based on molecular support, these three geographic assemblages are recognized as species using evolutionary species criteria: E. guttata, Elaphe slowinskii, and Elaphe emoryi [phylogeographic, maximum likelihood, maximum parsimony, bootstrap, Bayesian, Markov chain Monte Carlo, cornsnake, Cytochrome b, geographic lineages, E. guttta, E. slowinskii, and E. emoryi].

Molecular phylogeography of common garter snakes (Thamnophis sirtalis) in western North America: implications for regional historical forces

Complete ND2 and partial ND4 and cytochrome b mitochondrial DNA (mtDNA) sequences were analysed to evaluate the phylogeographic patterns of common garter snakes (Thamnophis sirtalis) in western North America. This species is widely distributed throughout North America, and exhibits extensive phenotypic variation in the westernmost part of its range. The overall phylogeographic pattern based on mtDNA sequences is concordant with results from studies of other species in this region, implicating historical vicariant processes during the Pleistocene and indicating bottleneck effects of recent dispersal into postglacial habitat. Indeed, the topology is statistically consistent with the hypothesis of both southern (Great Basin and California) and northern (Haida Gwaii) refugia. Specifically, we identified genetic breaks among three major clades: Northwest Coastal populations, Intermountain populations, and all California populations. The California clade contained the only other well-supported branching patterns detected; relationships among populations within the two northern clades were indistinguishable. These molecular splits contrast sharply with all prior geographical analyses of phenotypic variation in T. sirtalis in this region. Our results suggest that the extensive phenotypic variation in western T. sirtalis has been shaped more by local evolutionary forces than by shared common ancestry. Consequently, we consider all morphologically based subspecies designations of T. sirtalis in this region invalid because they do not reflect reciprocal monophyly of the mtDNA sequences.

[The snakes of Senegal: an annotated species list]

Between 1990 and 2001, the laboratory of Paludologie of IRD at Dakar collected over 5,500 snakes from all over Senegal. By studying this collection, an entirely new species was discovered for science and eight new species for Senegal. The presence of many specimens of rare species and the great number of localities from which snakes were collected also allowed us to solve several delicate taxonomic problems and better to specify the biogeography of Senegalese snakes. Currently, the presence in Senegal of at least 55 different species has been established with certainty. The data collected simultaneously on the burden of snakebites for public health shows considerable differences according to geographic area, with populations from south-eastern Senegal being more exposed to the risk of death by snakebite.

[A new species of snake of the genus Sibon (Serpentes: Colubridae) of the Caribbean slope of Costa Rica]

Sibon lamari, a new species of colubrid snake from northeastern Costa Rica is described on the basis of six specimens. The new form differs from the closely allied S. annulatus in color pattern, head size, subcaudal count, and number of labials bordering eye-orbit. This is the third species of Sibon, together with S. argus and S. longifrenis, possessing a green dorsal ground color in Costa Rica. Sibon lamari coexists sympatrically with S. annulatus, S. argus. S. longifrenis and S. nebulatus at the locality of Guayacán de Siquirres (Limón Province).

Phylogenetic relationships of xenodontine snakes inferred from 12S and 16S ribosomal RNA sequences

The phylogenetic relationships of xenodontine snakes are inferred from sequence analyses of portions of two mitochondrial genes (12S and 16S ribosomal RNA) in 85 species. Although support values for most of the basal nodes are low, the general pattern of cladogenesis observed is congruent with many independent molecular, morphological, and geographical data. The monophyly of xenodontines and the basal position of North American xenodontines in comparison with Neotropical xenodontines are favored, suggesting an Asian-North American origin of xenodontines. West Indian xenodontines (including endemic genera and members of the genus Alsophis) appear to form a monophyletic group belonging to the South American clade. Their mid-Cenozoic origin by dispersal using ocean currents is supported. Within South American mainland xenodontines, the tribes Hydropsini, Pseudoboini, and Xenodontini are monophyletic. Finally, our results suggest that some morphological and ecological traits concerning maxillary dentition, macrohabitat use, and foraging strategy have appeared multiple times during the evolution of xenodontine snakes.

Molecular systematics of new world gopher, bull, and pinesnakes (Pituophis: Colubridae), a transcontinental species complex

Pituophis melanoleucus (gopher, bull, and pinesnakes) is among the most widely distributed polytypic species complexes in North America, with most authors recognizing from a single transcontinental species (the melanoleucus complex, composed of 15 subspecies) to four (monotypic and polytypic) species. We used mitochondrial gene sequences from the two middle American species, P. deppei and P. lineaticollis, and from 13 subspecies from most of the range of the melanoleucus complex to test various phylogenetic hypotheses for Pituophis. Maximum parsimony and maximum likelihood methods identified the same major clades within Pituophis and indicated that two segments of the melanoleucus complex, the lodingi-melanoleucus-mugitus eastern pinesnake clade and the affinis-annectens-bimaris-catenifer-deserticola- sayi-ruthveni-vertebr alis clade from central and western United States and northern Mexico, represent divergent, allopatric lineages with no known intergradation zone. We recognize each of these two groupings as a different species. Our data also indicate that some ruthveni are more closely related to sayi than to other ruthveni. Nonetheless, ruthveni is an allopatric taxon diagnosable from its closest relatives by a combination of morphometric characters, and because it is likely that at least some of these traits are independent and genetically inherited, we interpret this as evidence that ruthveni has attained the status of independent evolutionary lineage, despite the fact that it retains strong genetic affinities with sayi. The endemic Baja Californian gopher snakes (bimaris and vertebralis) are considered by some taxonomists as a different species, P. vertebralis, but we discovered that these serpents belong to two different clades and hence we do not agree with the recognition of P. vertebralis as presently defined. In summary, we believe that three distinct species are included in the melanoleucus complex, Pituophis melanoleucus (sensu stricto), P. catenifer, and P. ruthveni, and that their recognition better represents the evolutionary diversity within this species complex.

Phylogeography of the California mountain kingsnake, Lampropeltis zonata (Colubridae)

The phylogeography of the California mountain kingsnake, Lampropeltis zonata, was studied using mitochondrial DNA sequences from specimens belonging to the seven recognized subspecies and collected throughout the range of the species. Maximum parsimony and maximum likelihood methods identified a basal split within L. zonata that corresponds to southern and northern segments of its distribution. The southern clade is composed of populations from southern California (USA) and northern Baja California, Mexico. The northern clade is divided into two subclades, a 'coastal' subclade, consisting of populations from the central coast of California and the southern Sierra Nevada Mountains of eastern California, and a 'northeastern' subclade, mainly comprised of populations north of the San Francisco Bay and from the majority of the Sierra Nevada. We suggest that past inland seaways in southwestern California and the embayment of central California constituted barriers to gene flow that resulted in the two deepest divergences within L. zonata. Throughout its evolutionary history, the northern clade apparently has undergone instances of range contraction, isolation, differentiation, and then expansion and secondary contact. Examination of colour pattern variation in 321 living and preserved specimens indicated that the two main colour pattern characters used to define the subspecies of L. zonata are so variable that they cannot be reliably used to differentiate taxonomic units within this complex, which calls into question the recognition of seven geographical races of this snake.

[Poisonous snakes of Europe]

Characteristics of poisonous snakes and their toxines are described. The appearance and biology of all European poisonous snakes, eight vipers (family Viperidae) and one opisthoglyph colubride snake (family Colubridae) are given in detail.

Protamines of reptiles

We have characterized for the first time the complete primary structure of the main protamine components of the sperm from four reptiles: Chrysemys picta (turtle), Elaphe obsoleta (snake), Anolis carolinensis (lizard), and Alligator mississipiensis (crocodilian). These species were chosen to represent one of each of the main phylogenetic branches of this taxonomic group. Comparison of these protamine sequences with those already available from other vertebrate groups allows us to define properly the chemical consensus composition of protamines and provides a unique insight into their molecular evolution and classification.