RESUMO
Although the recent advances on the relationship of its major groups, the systematics of the rich fauna of Neotropical snakes is far from being a consensus. In this sense, derived groups presenting continental distributions have represented a main challenge. The taxonomy of the snake tribe Echinantherini is one of the most contentious among the diverse family known as Dipsadidae. The tribe is poorly sampled in phylogenetic studies, resulting in conflicting hypotheses of relationships among its taxa. Moreover, several rare and micro endemic species of Echinantherini have never been evaluated within a comprehensive phylogenetic framework. Here, we assess for the first time the phylogenetic position of the rare Echinanthera amoena within Echinantherini. We based our analyses on a comprehensive multilocus dataset including 14 of the 16 species described for the tribe. Our results support the monophyly of Echinantherini and strongly indicate E. amoena as a unique lineage, phylogenetically positioned apart from all other congeners. From the three current genera (Echinanthera, Taeniophallus, and Sordellina) our results indicate that Echinanthera and Taeniophallus are paraphyletic, since the T. affinis species group is positioned as sister to Echinanthera (except E. amoena) clustering apart from the clade formed by the T. brevirostris and T. occipitalis groups. We describe new genera for the T. affinis and T. occipitalis species groups and an additional monospecific genus for E. amoena. Although we did not evaluate the phylogenetic position of T. nebularis, we described a new genus and removed it from Echinantherini since its morphology strikingly departs from all species now included in the tribe. Finally, we redefine the genera Echinanthera and Taeniophallus and we provide comments about further directions to study the biogeography and the evolution of morphological traits in Echinantherini.
RESUMO
Although the recent advances on the relationship of its major groups, the systematics of the rich fauna of Neotropical snakes is far from being a consensus. In this sense, derived groups presenting continental distributions have represented a main challenge. The taxonomy of the snake tribe Echinantherini is one of the most contentious among the diverse family known as Dipsadidae. The tribe is poorly sampled in phylogenetic studies, resulting in conflicting hypotheses of relationships among its taxa. Moreover, several rare and micro endemic species of Echinantherini have never been evaluated within a comprehensive phylogenetic framework. Here, we assess for the first time the phylogenetic position of the rare Echinanthera amoena within Echinantherini. We based our analyses on a comprehensive multilocus dataset including 14 of the 16 species described for the tribe. Our results support the monophyly of Echinantherini and strongly indicate E. amoena as a unique lineage, phylogenetically positioned apart from all other congeners. From the three current genera (Echinanthera, Taeniophallus, and Sordellina) our results indicate that Echinanthera and Taeniophallus are paraphyletic, since the T. affinis species group is positioned as sister to Echinanthera (except E. amoena) clustering apart from the clade formed by the T. brevirostris and T. occipitalis groups. We describe new genera for the T. affinis and T. occipitalis species groups and an additional monospecific genus for E. amoena. Although we did not evaluate the phylogenetic position of T. nebularis, we described a new genus and removed it from Echinantherini since its morphology strikingly departs from all species now included in the tribe. Finally, we redefine the genera Echinanthera and Taeniophallus and we provide comments about further directions to study the biogeography and the evolution of morphological traits in Echinantherini.
RESUMO
Studying species interactions in nature often requires elaborated logistics and intense fieldwork. The difficulties in such task might hinder our ability to answer questions on how biotic interactions change with the environment. Fortunately, a workaround to this problem lies within scientific collections. For some animals, the inspection of preserved specimens can reveal the scars of past antagonistic encounters, such as predation attempts. A common defensive behaviour that leaves scars on animals is autotomy, the loss of a body appendage to escape predation. By knowing the collection site of preserved specimens, it is possible to assess the influence of organismal biology and the surrounding environment in the occurrence of autotomy. We gathered data on tail loss for 8189 preserved specimens of 33 snake and 11 amphisbaenian species to investigate biological and environmental correlates of autotomy in reptiles. We applied generalized linear mixed effect models to evaluate whether body size, sex, life-stage, habitat use, activity pattern, biome, tropicality, temperature and precipitation affect the probability of tail loss in limbless reptiles. We observed autotomy in 23.6 per cent of examined specimens, with 18.7% of amphisbaenian and 33.4% of snake specimens showing tail loss. The probability of tail loss did not differ between snakes and amphisbaenians, but it was higher among large-sized specimens, particularly in adults and females. Chance of tail loss was higher for diurnal and arboreal species, and among specimens collected in warmer regions, but it was unaffected by biome, precipitation, and tropicality. Autotomy in limbless reptiles was affected by size-dependent factors that interplay with ontogeny and sexual dimorphism, although size-independent effects of life-stage and sex also shaped behavioural responses to predators. The increase in probability of tail loss with verticality and diurnality suggests a risk-balance mechanism between species habitat use and activity pattern. Although autotomy is more likely in warmer regions, it seems unrelated to seasonal differences in snakes and amphisbaenians activity. Our findings reveal several processes related to predator–prey interactions involving limbless reptiles, demonstrating the importance of scientific collections to unveil ecological mechanisms at different spatio-temporal scales.
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Tantilla is one of the most diverse genera among colubrids, with 67 species arranged in six phenotypically recognized species groups. Tantilla boipiranga is the most recently described species within the T. melanocephala group, and it was described based on a small type series, collected in the rupestrian grasslands of south-eastern Brazil. The morphological diversity and the phylogenetic affinity of this species remain poorly known. Here, based on the assessment of recently collected specimens in combination with results of a molecular phylogenetic analysis, we evaluate the morphological variation within T. boipiranga and its phylogenetic position. Our analyses confirm T. boipiranga as genetically distinct from its generic counterparts, and diagnosable based on a combination of colour pattern, meristic counts, and hemipenial morphology. However, contrary to its original description, the hemipenial ornamentation does not differen-tiate T. boipiranga from the highly variable T. melanocephala. In our phylogenetic analysis, T. boipiranga is retrieved as a monophyletic group, nested within the diversity of T. melanocephala and sister to a clade composed by specimens from south-eastern Brazil. Tantilla melanocephala is recovered as a highly diverse lineage, indicating the possible presence of undescribed species. Additionally, our analysis indicates that the T. coronata and T. planiceps species group are mono-phyletic, while the T. taeniata species group is paraphyletic and the only sampled species for the T. calamarina group is nested within the T. melanocephala group. Our results suggest that the phenotypic evolution within the genus is probably more complex than previously recognized, and some colouration patterns used to define the groups can in fact represent phenotypical convergences. Moreover, our phylogenetic analysis suggests a strong signal of geographical structure in the tree topology. Three main geographical lineages were found, a North American, a South American and a Central Ameri-can. The first two lineages were recovered as monophyletic, while the latter is paraphyletic, with Central American species positioned as sister groups of both, the North American and the South American clades. Although a more comprehensive phylogenetic analysis is needed, our study strongly indicates the existence of hidden diversity within the T. melanocephala group and that Tantilla represents an ideal model to evaluate the validity of phenotypical groups in snake systematics and to study the driven mechanisms of morphological evolution.
RESUMO
The secretive behavior and life history of snakes makes studying their biology, distribution, and the epidemiology of venomous snakebite challenging. One of the most useful, most versatile, and easiest to collect types of biological data are photographs, particularly those that are connected with geographic location and date-time metadata. Photos verify occurrence records, provide data on phenotypes and ecology, and are often used to illustrate new species descriptions, field guides and identification keys, as well as in training humans and computer vision algorithms to identify snakes. We scoured eleven online and two offline sources of snake photos in an attempt to collect as many photos of as many snake species as possible, and attempt to explain some of the inter-species variation in photograph quantity among global regions and taxonomic groups, and with regard to medical importance, human population density, and range size. We collected a total of 725,565 photos—between 1 and 48,696 photos of 3098 of the world's 3879 snake species (79.9%), leaving 781 “most wanted” species with no photos (20.1% of all currently-described species as of the December 2020 release of The Reptile Database). We provide a list of most wanted species sortable by family, continent, authority, and medical importance, and encourage snake photographers worldwide to submit photos and associated metadata, particularly of “missing” species, to the most permanent and useful online archives: The Reptile Database, iNaturalist, and HerpMapper.
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Erythrolamprus Boie, 1826 is a highly diverse dipsadid snake genus, ranging from Central America south to Argentina and Uruguay. In this work, we reassess the taxonomic status of specimens previously identified as Erythrolamprus poecilogyrus schotti (Schlegel, 1837) from the savannah habitats of Roraima state, northern Brazil, Guyana, and Bolívarstate, Venezuela. Based on novel molecular and morphological evidence, we conclude that these specimens represent a distinct, diagnosable and reciprocally monophyletic taxon. We here describe it as a new species. Furthermore, we comment on the taxonomy of other Erythrolamprus spp
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Phalotris Cope, 1862 is a fossorial dipsadid snake genus that encompasses 15 species, distributed mainly in open areas from Northeastern Brazil to Southern Argentina. Some of its species are known from small series, and there is little to no knowledge on their morphological variation and species delimitations. In this work, we analyze the taxonomic status of Phalotris cerradensisSilveira, 2020, a recently described species known from a single specimen, and provide evidence for its synonymy with Phalotris concolorFerrarezzi, 1993.
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The criteria used by previous authors to define colour aberrancies of snakes, particularly albinism, are varied and terms have widely been used ambiguously. The aim of this work was to review genetically based aberrant colour morphs of wild Neotropical snakes and associated terminology. We compiled a total of 115 cases of conspicuous defective expressions of pigmentations in snakes, including melanin (black/brown colour), xanthins (yellow), and erythrins (red), which involved 47 species of Aniliidae, Boidae, Colubridae, Elapidae, Leptotyphlopidae, Typhlopidae, and Viperidae. Most of them were hypopigmented conditions, mainly amelanism, but also anerythrism, axanthism, hypomelanism, leucism, piebaldism, and albinism (total absence of pigments). Hyperpigmented aberrancies were mostly melanism and xanthism, plus a few instances of erythrism. No associations with diurnality and fossorial behaviour were observed, neither for blanched nor hyperpigmented aberrancies. A discussion of the terms most commonly used for wild snakes is provided, with an account of cases of aberrant colourations in other South American reptiles. Finally, we propose a simple classification framework of wild snake colour aberrancies based on predominant dorsal colour and eye pigmentation for the adoption of a standardized terminology, which may be applicable to other squamates and chelonians. We advocate the use of a more accurate terminology in the scientific literature that would avoid the use of confusing terms like “partial albinism”.
RESUMO
Pseudoautotomy is presumably a derived character within Lepidosauria and occurs in taxa that have lost the ability to perform autotomy. In general, species capable of employing pseudoautotomy as a defensive strategy against predators present a high frequency of damaged tails in series deposited in herpetological collections. We assessed data from three largely sympatric Echinanthera species in the Brazilian Atlantic Rainforest (E. cephalostriata, E. cyanopleura, and E. undulata) to test previous assumptions that species of Echinanthera use their tails defensively. This hypothesis derives from anecdotal observations during fieldwork and is reinforced by the number of specimens presenting tail breakage in scientific collections. In general, the frequency of damaged tails in these species resembles that of others in which pseudoautotomy has been demonstrated. Statistical analyses revealed no differences in tail breakage frequencies between sexes for the analyzed species or between the two geographical groups defined for E. cyanopleura. In contrast, we detected a significant difference between snout-vent length and sex regarding pseudoautotomy probability for E. cyanopleura, with a positive relationship between tail breakage frequency and snout-vent length.
RESUMO
Sexual dimorphism in snakes has been mainly evaluated for size and number of some morphological traits, but few studies address on sexual shape dimorphism. Here we evaluated the existence of sexual size and shape dimorphism in the semi-fossorial snake Atractus reticulatus. We use linear and geometric morphometrics to evaluate differences between sexes and among different ontogenetic stages (neonates, juveniles and adults). We have shown that A. reticulatus is sexually dimorphic for some traits such as body length and head shape, with females being larger and having more robust heads than males, but the sexes do not differ in head size. Males and females are sexually dimorphic in head shape even in neonates, suggesting that this differentiation is prenatal. Differences in head shape may be associated with trophic segregation, allowing females to feed on larger prey than males. Body size dimorphism progressively increases throughout the ontogenetic stages, which is possibly related to the late sexual maturation of females and/or different growth rates between the sexes. We also found that males and females shows some sex-specific patterns towards static and ontogenetic allometry, with males showing stronger predictive response on static allometry than females, whereas females have ontogenetic allometry, but males do not. Additionally, the allometric slopes in A. reticulatus between sexes converge by presenting similar shapes as head size increases, an expected result for sexes with similar lifestyles. Further investigation on some physiological and natural history aspects in Atractus will be particularly useful for a better understanding of the significance of the morphological differences found in this study.