Phenotypic divergence between seasnake (Emydocephalus annulatus) populations from adjacent bays of the New Caledonian Lagoon

Populations of widespread species often differ in phenotypic traits, although rarely in such a dramatic fashion as revealed by research on turtle‐headed seasnakes (Emydocephalus annulatus). These snakes are highly philopatric, with mark–recapture studies showing that the interchange of individuals rarely occurs even between two adjacent bays (separated by < 1.2 km) in Noumea, New Caledonia. Data on > 500 field‐captured snakes from these two bays reveal significant differences between these two locations in snake morphology (mean body length, relative tail length, head shape), colour, ecology (body condition, growth rate, incidence of algal fouling), behaviour (antipredator tactics), and locomotor performance. For some traits, the disparity was very marked (e.g. mean swimming speeds differed by > 30%). The causal bases for these phenotypic divergences may involve founder effects, local adaptation, and phenotypic plasticity. The spatial divergence in phenotypic traits offers a cautionary tale both for researchers (sampling of only a few populations may fail to provide a valid overview of the morphology, performance, and behaviour of a species) and managers (loss of local populations may eliminate distinctive genetic variation). © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Differential Effects of an Intense Wildfire on Survival of Sympatric Snakes

Abstract: We analyzed 16 years of mark-recapture data to investigate whether a wildfire influenced survival of an arboreal ambush-forager (broad-headed snake [Hoplocephalus bungaroides]) and a terrestrial active forager (small-eyed snake Cryptophis nigrescens). We predicted that wildfire would cause direct mortality and reduce subsequent survival of both snake species. Contrary to this prediction, wildfire did not affect abundance of broad-headed snakes, but abundance of small-eyed snakes decreased by 48% after the wildfire. Estimated annual survival of small-eyed snakes was 37% lower after fire (s=0.47, SE=0.07) than before fire (s=0.74, SE=0.05). Prescribed burning may be a suitable tool for creating open habitat mosaics for the endangered broad-headed snake.     

Spatial ecology of arboreal snakes (Hoplocephalus stephensii,Elapidae) in an eastern Australian forest

Abstract Stephens' Banded Snakes (Hoplocephalus stephensii Krefft 1869) are large (to 1 m), highly arboreal elapid snakes, restricted to mesic forested areas along the eastern coast of Australia. Radiotelemetric monitoring of 16 individuals at Whian Whian State Forest in north‐eastern New South Wales over 25 months provided the first data on spatial ecology of this threatened taxon. Two major influences on movements by Stephens' Banded Snakes were identified: the distribution of large hollow‐bearing trees, and the avoidance of conspecifics. Radiotracked snakes were sedentary inside tree hollows for extended periods (mean = 8 days) during their active season, interrupted by occasional long (mean = 124 m) nocturnal movements to another shelter tree. Snakes travelled on the ground rather than within the canopy, and thus were potentially exposed to terrestrial predators. Although the home ranges of the radiotracked snakes overlapped substantially (mean = 27%), simultaneous occupancy of ‘shared’ shelter trees was less common than expected by chance. Hence, we conclude that adult Stephens' Banded Snakes generally avoid the presence of conspecifics. Snakes used from five to 30 shelter trees and home ranges of male snakes were larger than those of females (mean = 20.2 vs 5.4 ha). The large spatial scale of these movements, and limited overlap among individuals, means that a viable population of this taxon requires a large area of contiguous forest. This requirement may explain why the species has not persisted in small forest fragments.     

Does foraging mode influence life history traits? A comparative study of growth,maturation and survival of two species of sympatric snakes from south‐eastern Australia

Abstract Theory predicts that compared with active searchers, ambush foragers should have lower rates of energy intake, slower growth, and higher survival rates. We tested these predictions with data on two species of sympatric, saurophagous, small‐bodied, viviparous elapid snakes: the broad‐headed snake, Hoplocephalus bungaroides, and the small‐eyed snake, Rhinoplocephalus nigrescens. Demographic parameters and growth curves for both species were estimated from a long‐term (9 years) mark‐recapture study in Morton National Park, south‐eastern Australia. The ambush predator (H. bungaroides) displayed slower juvenile growth and later maturation (5 years for males, 6 years for females) than did the active forager (R. nigrescens, 3 years). Litter sizes were similar in both species, but reproductive frequency was higher in R. nigrescens (90–100%) than in H. bungaroides (50%). Juvenile survival was lower in the active searcher (31%) than in the ambush forager (55%), but adult survivorship was similar (74% vs 82%). Our results support the hypothesis that ambush foragers display ‘slow’ life history traits, but additional phylogenetically independent comparisons are needed to evaluate the generality of this pattern.     

Phylogenetic relationships of colubroid snakes based on mitochondrial DNA sequences

We used a 694 bp length of the mitochondrial ND4 gene from 40 genera to infer phylogenetic relationships among colubroid snakes. The goals of this study were to identify conserved subsets of ND4 sequence data that could be used to address (1) which nominal higher-level colubroid taxa are monophyletic, and (2) the relationships among the monophyletic lineages identified. Use of transversions only proved the most reliable and efficient means of retrieving colubroid relationships. Transversion parsimony and neighbour-joining analyses identify similar monophyletic higher-level taxa, but relationships among these lineages differ considerably between the two analyses. These differences were affected by the inclusion/exclusion of (1) transitions, (2) autapomorphies, and (3) the boid outgroups. Saturation effects among the transitions, uninformativeness of autapomorphies for clustering taxa, and long-branch and base-compositional problems among the boids lead us to regard the tree resulting from transversion parsimony analysis rooted with Acrochordus as the best current estimate of colubroid phylogenetic relationships. However, several aspects of this proposed phylogeny need further testing (e.g. the apparent diphyly of Natricinae is especially controversial). Relationships retrieved using all colubroid taxa are not obtained when sparsely or unevenly sampled experimental subsets of taxa are used instead, suggesting that long-branch problems can severely compromise elucidation of colubroid relationships if limited taxonomic sampling strategies are followed. We discuss the importance of this finding for previous molecular attempts to assess colubroid relationships. Our analyses confirm the historical validity of several nominal colubroid families and subfamilies, establish polyphyly of a few, but generally fail to resolve relationships among the monophyletic taxa we identify. More conservative character information will be required to confidently resolve the last issue.     

Novel microsatellite loci identified from the Australian eastern small‐eyed snake (Elapidae: Rhinocephalus nigrescens) and cross species amplification in the related genus Suta

A total of 15 microsatellite primers pairs were developed for the Australian small‐eyed snake Rhinoplocephalus nigrescens. Five primers were used to screen 93 individuals of R. nigrescens and were also tested against eight species of the closely related genus Suta. Allelic diversity in R. nigrescens was high in three loci (12–27) and there was high heterozygosity (0.58–0.82). Observed heterozygosity did not deviate from Hardy–Weinberg expectations for the five loci tested. These primers will be useful in studies of population genetics and mating systems of small‐eyed snakes and related species.     

舟山眼镜蛇对光暗周期加热光源反应所导致的体温变化

用 7条舟山眼镜蛇 (Najaatra)研究动物对光暗周期加热光源反应所导致的体温变化。设计两项实验 ,每项实验历时 9d。实验一光照期覆盖整个白天 ,实验二光照期覆盖整个晚上。眼镜蛇仅在加热光源开启期间进行体温调节 ,但光照期内任何阶段都未发现所有个体同时处于热活动状态。两项实验中热活动个体百分比的时间变化显著 ,实验二热活动个体百分比波动相对大于实验一。在加热光源开启期间 ,实验一热活动眼镜蛇的百分比总体上大于实验二。在两项实验中 ,热活动眼镜蛇体温的时间变化都不显著。实验一热活动眼镜蛇的体温高于实验二 ,而两项实验中不处于热活动状态的眼镜蛇的平均体温无显著差异。实验一热活动眼镜蛇 (31 1±0 8°C)选择的体温上限高于实验二眼镜蛇 (2 6 0± 0 9°C)。在两项实验的任何时间段内 ,眼镜蛇的体温都不低于环境温度。     

Genetic Connectivity among Populations of an Endangered Snake Species from Southeastern Australia (Hoplocephalus bungaroides, Elapidae)

For endangered species that persist as apparently isolated populations within a previously more extensive range, the degree of genetic exchange between those populations is critical to conservation and management. A lack of gene flow can exacerbate impacts of threatening processes and delay or prevent colonization of sites after local extirpation. The broad-headed snake, Hoplocephalus bungaroides, is a small venomous species restricted to a handful of disjunct reserves near Sydney, Australia. Mark-recapture studies have indicated low vagility for this ambush predator, suggesting that gene flow also may be low. However, our analyses of 11 microsatellite loci from 163 snakes collected in Morton National Park, from six sites within a 10-km diameter, suggest relatively high rates of gene flow among sites. Most populations exchange genes with each other, with one large population serving as a source area and smaller populations apparently acting as sinks. About half of the juvenile snakes, for which we could reliably infer parentage, were collected from populations other than those in which we collected their putative parents. As expected from the snakes' reliance on rocky outcrops during cooler months of the year, most gene flow appears to be along sandstone plateaux rather than across the densely forested valleys that separate plateaux. The unexpectedly high rates of gene flow on a landscape scale are encouraging for future conservation of this endangered taxon. For example, wildlife managers could conserve broad-headed snakes by restoring habitats near extant source populations in areas predicted to be least affected by future climate change.     

Generalization of predator recognition: Velvet geckos display anti-predator behaviours in response to chemicals from non-dangerous elapid snakes

Many prey species detect chemical cues from predators and modify their behaviours in ways that reduce their risk of predation. Theory predicts that prey should modify their anti-predator responses according to the degree of threat posed by the predator. That is, prey should show the strongest responses to chemicals of highly dangerous prey, but should ignore or respond weakly to chemicals from non-dangerous predators. However, if anti-predator behaviours are not costly, and predators are rarely encountered, prey may exhibit generalised antipredator behaviours to dangerous and non-dangerous predators. In Australia, most elapid snakes eat lizards, and are therefore potentially dangerous to lizard prey. Recently, we found that the nocturnal velvet gecko Oedura lesueurii responds to chemicals from dangerous and non-dangerous elapid snakes, suggesting that it displays gen-eralised anti-predator behaviours to chemicals from elapid snakes. To explore the generality of this result, we videotaped the be-haviour of velvet geckos in the presence of chemical cues from two small elapid snakes that rarely consume geckos: the nocturnal golden-crowned snake Cacophis squamulosus and the diurnal marsh snake Hemiaspis signata. We also videotaped geckos in tri-als involving unsceted cards (controls) and cologne-scented cards (pungency controls). In trials involving Cacophis and Hemi-aspis chemicals, 50% and 63% of geckos spent long time periods (> 3 min) freezing whilst pressed flat against the substrate, re-spectively. Over half the geckos tested exhibited anti-predator behaviours (tail waving, tail vibration, running) in response to Ca-cophis (67%) or Hemiaspis (63%) chemicals. These behaviours were not observed in control or pungency control trials. Our re-sults support the idea that the velvet gecko displays generalised anti-predator responses to chemical cues from elapid snakes. Generalised responses to predator chemicals may be common in prey species that co-occur with multiple, ecologically similar, dangerous predators.     

On the affinities of the burrowing asps Atractaspis (Serpentes: Atractaspididae)

An analysis is presented of a sample of Atractaspididae ( sensu McDowell) plus Macrelaps, Aparallactus, Apostolepis, Elapomorphus, Homoroselaps and six genera of African elapids in respect of squamation, reproductive organs, skull, head muscles and vertebrae. Homoroselaps is linked with the African Elapidae and is returned to that family. Scattered special resemblances to atractaspids are interpreted as homoplasies. Some interrelationships of the African elapids are suggested. The South American Apostolepis and Elapomorphus represent a separate, possibly related, lineage at the same grade level as the African Atractaspididae. Macrelaps and Aparallactus are transferred to the Atractaspididae. Atractaspis emerges as a low grade but highly divergent member of the family. Macrelaps is the most primitive. The other taxonomic units are completely resolved with, however, the anomaly of reversal to the seemingly primitive states of six characters in four lineages (six genera). The Atractaspididae, Apostolepis and Elapomorphus are regarded as low grade members of the Caenophidia. It is suggested that early in the history of the caenophidian lineage a venom apparatus was acquired, prior to the major radiation of the group. Many descendent lineages show regression of the venom apparatus.