Evolutionary relationships between reptiles inferred from the comparison of their ITS2 sequences

The reptile phylogeny is poorly studied, and many existing hypotheses are controversial. In this study, the ITS2 regions of 43 species of lizards, snakes, turtles, and crocodiles were cloned and sequenced in addition to eight ITS2 sequences of amphibians, reptiles, and birds already present in the database. The ITS2 of reptiles, similarly to other vertebrates, contain short conserved (consensus) regions, alternating with variable regions (DI, DII, and DIII), which are potentially capable of forming stable secondary structures. These functionally neutral rDNA regions, separating the consensus regions, are substantially different in size, as well as in the primary and secondary structure. Sequences of the ITS2 variable regions were aligned using the GeneBee Molecular Biology Server software program with subsequent automated construction of prescribed trees. The trees for all three variable regions were highly similar, enabling certain conclusions on the evolutionary history of reptiles.     

Unusually high zinc concentrations in snake plasma, with observations on plasma zinc concentrations in lizards, turtles and alligators

We provide evidence that normal plasma zinc levels in snakes are in the same range as the elevated zinc levels associated with haemolytic anaemia and fatal zinc toxicosis in dogs, and with weight loss and anorexia in crocodiles that had ingested coins with high zinc content. Blood plasma samples from large representative groups of snakes, lizards, turtles and alligators were analysed for zinc content by atomic absorption spectrophotometry. Plasma zinc levels in all snake species were five to 50-fold greater than levels reported in mammals. Plasma zinc levels in lizards and turtles were also higher than those of mammals, but significantly lower than those of snakes. Plasma zinc levels in alligators were in the same range as mammals and birds. After prolonged dialysis of snake plasma, 76% of the zinc remains in the retentate, suggesting the presence of a plasma protein with a strong affinity for the metal. Zinc levels vary significantly among the taxonomic groups, emphasizing the common evolutionary origin of crocodiles and birds and their divergence from the other reptiles.     

Parathyroid Glands in Reptiles

The parathyroid glands in reptiles generally develop from thethird and fourth pharyngeal pouches. In lizards and crocodiles,usually only one pair of glands (from the third pouch) persists,while turtles and snakes generally retain both pairs of glandsin adults. The glands consist of cell cords and are similarin structure to those of birds and mammals. A common featureof reptilian parathyroids is the organization of cells arounda lumen in a follicular arrangement. The few physiological studieswhich have been made indicate that parathyroid function in reptilesis in many respects similar to that of mammals. For example,in lizards, parathyroidectomy results in tetanic convulsionsand lowered values of plasma calcium, while administration ofparathyroid extract increases mine phosphate and serum calciumin turtles, and increases the number of osteoclasts in boneof lizards and turtles. However, there are some obvious differencesbetween parathyroid function in reptiles and mammals, on whichmuch more work is needed.     

山西垣曲河堤组寨里段的低等四足类动物群

本文记述了我国晚始新世的一低等四足类动物群,包括三种蜥蜴和两种鳄类.其中的宽额半鳄蜥(Hemishinisaurus latifrons gen. et sp. nov.)是我国首次发现的异蜥科化石;垣曲响蜥(Tinosaurus yuanquensis sp. nov.)是响蜥属在我国的最晚代表.     

More than 1000 ultraconserved elements provide evidence that turtles are the sister group of archosaurs

We present the first genomic-scale analysis addressing the phylogenetic position of turtles, using over 1000 loci from representatives of all major reptile lineages including tuatara. Previously, studies of morphological traits positioned turtles either at the base of the reptile tree or with lizards, snakes and tuatara (lepidosaurs), whereas molecular analyses typically allied turtles with crocodiles and birds (archosaurs). A recent analysis of shared microRNA families found that turtles are more closely related to lepidosaurs. To test this hypothesis with data from many single-copy nuclear loci dispersed throughout the genome, we used sequence capture, high-throughput sequencing and published genomes to obtain sequences from 1145 ultraconserved elements (UCEs) and their variable flanking DNA. The resulting phylogeny provides overwhelming support for the hypothesis that turtles evolved from a common ancestor of birds and crocodilians, rejecting the hypothesized relationship between turtles and lepidosaurs.     

Neuroendocrine peptides (insulin, pancreatic polypeptide, neuropeptide Y, galanin, somatostatin, substance P, and neuropeptide gamma) from the desert tortoise, Gopherus agassizii.

The traditional view that Testudines (tortoises and turtles) should be regarded as the surviving clade of the anapsid reptiles rather than classified with the diapsid reptiles (snakes, lizards, and crocodiles) has recently been challenged. Neuropeptide Y, neuropeptide gamma, and somatostatin-14 were isolated from an extract of the brain, substance P and galanin from an extract of the intestine, and insulin and pancreatic polypeptide from an extract of the pancreas of the desert tortoise, Gopherus agassizii. Despite that crocodilians did not appear until the late Triassic, the amino acid sequences of the tortoise peptides resemble those of the American alligator quite closely. The primary structures of neuropeptide Y, somatostatin-14, and neuropeptide gamma are the same in tortoise and alligator. The primary structures of substance P, insulin, galanin, and pancreatic polypeptide in the two species differ by 1, 3, 5, and 8 amino acid residues, respectively. Although fewer neurohormonal peptides from squamates (lizards and snakes) have been characterized, the primary structures of neuropeptide gamma, insulin, and pancreatic polypeptide from the Burmese python and the desert tortoise differ by 3, 8, and 18 residues, respectively. The data suggest, therefore, a closer phylogenetic relationship between Testudines and Crocodilians than that derived from 'classical' analyses based on morphological criteria and the fossil record.     

Reptiles as a food resource

Reptiles have served as an important source of protein for human populations around the world. Exploitation for food is heaviest in the tropical and sub-tropical regions, but also occurs in temperate areas. Of all reptiles, turtles are the most heavily exploited for human consumption. High, unsustainable levels of exploitation for food are directly responsible for the precarious conservation status of many turtles. Crocodilians, snakes, and lizards may be locally important food sources, however, with the exception of a few lizard species, they are exploited in a less intense and generally non-commercial manner for human consumption. In comparison, the commercial skin trade poses a far greater threat to the survival of crocodilians as well as certain large snakes and lizards. Recent field reports have implicated the south east Asian medicinal trade as a growing threat to reptiles, especially turtles and snakes. There are few unequivocal examples of managed harvest programmes for reptiles that are economically and culturally viable, as well as biologically sustainable. Given the economic importance of reptiles as sources of protein and other highly valued commodities, it is imperative that more attention be focused on the development of sustainable use programmes for these species.     

Strong conservation of the bird Z chromosome in reptilian genomes is revealed by comparative painting despite 275 million years divergence

The divergence of lineages leading to extant squamate reptiles (lizards, snakes, and amphisbaenians) and birds occurred about 275 million years ago. Birds, unlike squamates, have karyotypes that are typified by the presence of a number of very small chromosomes. Hence, a number of chromosome rearrangements might be expected between bird and squamate genomes. We used chromosome-specific DNA from flow-sorted chicken (Gallus gallus) Z sex chromosomes as a probe in cross-species hybridization to metaphase spreads of 28 species from 17 families representing most main squamate lineages and single species of crocodiles and turtles. In all but one case, the Z chromosome was conserved intact despite very ancient divergence of sauropsid lineages. Furthermore, the probe painted an autosomal region in seven species from our sample with characterized sex chromosomes, and this provides evidence against an ancestral avian-like system of sex determination in Squamata. The avian Z chromosome synteny is, therefore, conserved albeit it is not a sex chromosome in these squamate species.     

Trends in the evolution of reptilian chromosomes

Reptiles are a karyologically heterogeneous group, where some orders and suborders exhibit characteristics similar to those of anamniotes and others share similarities with homeotherms. The class also shows different evolutionary trends, for instance in genome and chromosome size and composition. The turtle DNA base composition is similar to that of mammals, whereas that of lizards and snakes is more similar to that of anamniotes. The major karyological differences between turtles and squamates are the size and composition of the genome and the rate at which chromosomes change. Turtles have larger and more variable genome sizes, and a greater amount of middle repetitive DNA that differs even among related species. In lizards and snakes size of the genome are smaller, single-copy DNA is constant within each suborder, and differences in repetitive DNA involve fractions that become increasingly heterogeneous with widening phylogenetic distance. With regard to variation in karyotype morphology, turtles and crocodiles show low variability in chromosome number, morphology, and G-banding pattern. Greater variability is found among squamates, which have a similar degree of karyotypic change-as do some mammals, such as carnivores and bats-and in which there are also differences among congeneric species. An interesting relationship has been highlighted in the entire class Reptilia between rates of change in chromosomes, number of living species, and rate of extinction. However, different situations obtain in turtles and crocodiles on the one hand, and squamates on the other. In the former, the rate of change in chromosomes is lower and the various evolutionary steps do not seem to have entailed marked chromosomal variation, whereas squamates have a higher rate of change in chromosomes clearly related to the number of living species, and chromosomal variation seems to have played an important role in the evolution of several taxa. The different evolutionary trends in chromosomes observed between turtles and crocodiles on the one hand and squamates on the other might depend on their different patterns of G-banding.     

Mass extinctions do not explain skew in interspecific body size distributions

In several higher animal taxa, such as mammals and birds, the distribution of species body sizes is heavily skewed towards small size. Previous studies have suggested that small‐bodied organisms are less prone to extinction than large‐bodied species. If small body size is favourable during mass extinction events, a post mass extinction excess of small‐bodied species may proliferate and maintain skewed body size distributions sometime after. Here, we modelled mass extinctions and found that even unrealistically strong body mass selection has little effect on the skew of interspecific body size distributions. Moreover, selection against large body size may, counter intuitively, skew size distributions towards large body size. In any case, subsequent evolutionary diversification rapidly erases these rather small effects mass extinctions may have on size distributions. Next, we used body masses of extant species and phylogenetic methods to investigate possible changes in body size distributions across the Cretaceous–Paleogene (K‐Pg) mass extinction. Body size distributions of extant clades that originated during the Cretaceous are on average more skewed than their subclades that originated during the Paleogene, but the difference is only minor in mammals, and in birds, it can be explained by a positive relationship between species richness and skewness that is also present in clades that originated after the transition. Hence, we cannot infer from extant species whether the K‐Pg mass extinctions were size‐selective, but they are not the reason why most extant bird and mammal species are small‐bodied.     

Unraveling the consequences of the terminal Pleistocene megafauna extinction on mammal community assembly

Recent studies connecting the decline of large predators and consumers with the disintegration of ecosystems often overlook that this natural experiment already occurred. As recently as 14 ka, tens of millions of large‐bodied mammals were widespread across the American continents. Within 1000 yr of the arrival of humans, ～ 80% were extinct including all > 600 kg. While the cause of the late Pleistocene (LP) extinction remains contentious, largely overlooked are the ecological consequences of the loss of millions of large‐bodied animals. Here, we examine the influence of the LP extinction on a local mammal community. Our study site is Hall's Cave in the Great Plains of Texas, which has unparalleled fine‐grained temporal resolution over the past 20 ka, allowing characterization of the community before and after the extinction. In step with continental patterns, this community lost 80% of large‐bodied herbivores and 20% of apex predators at the LP extinction. Using tightly constrained temporal windows spanning full glacial to modern time periods and comprehensive faunal lists, we reconstruct mammal associations and body size distributions over time. We find changes in alpha and beta diversity, and in the statistical moments associated with periods of climate change as well as with the LP extinction event. Additionally, there is a fundamental change in the composition of herbivores, with grazers being replaced by frugivores/granivores starting about 15 ka; the only large‐bodied grazer remaining today is the bison Bison bison. Moreover, the null model program PAIRS reveals interesting temporal patterns in the disassociation or co‐occurrence of species through the terminal Pleistocene and Holocene. Extinct species formed more significant associations than modern ones, and formed more aggregated pairs than do modern species. Further, negative species associations were about three times stronger than positive ones, suggesting that competitive interactions or environmental filtering are a strong force in community structure.     

Extinct or still out there? Disentangling influences on extinction and rediscovery helps to clarify the fate of species on the edge

Each year, two or three species that had been considered to be extinct are rediscovered. Uncertainty about whether or not a species is extinct is common, because rare and highly threatened species are difficult to detect. Biological traits such as body size and range size are expected to be associated with extinction. However, these traits, together with the intensity of search effort, might influence the probability of detection and extinction differently. This makes statistical analysis of extinction and rediscovery challenging. Here, we use a variant of survival analysis known as cure rate modelling to differentiate factors that influence rediscovery from those that influence extinction. We analyse a global data set of 99 mammals that have been categorized as extinct or possibly extinct. We estimate the probability that each of these mammals is still extant and thus estimate the proportion of missing (presumed extinct) mammals that are incorrectly assigned extinction. We find that body mass and population density are predictors of extinction, and body mass and search effort predict rediscovery. In mammals, extinction rate increases with body mass and population density, and these traits act synergistically to greatly elevate extinction rate in large species that also occurred in formerly dense populations. However, when they remain extant, larger‐bodied missing species are rediscovered sooner than smaller species. Greater search effort increases the probability of rediscovery in larger species of missing mammals, but has a minimal effect on small species, which take longer to be rediscovered, if extant. By separating the effects of species characteristics on extinction and detection, and using models with the assumption that a proportion of missing species will never be rediscovered, our new approach provides estimates of extinction probability in species with few observation records and scant ecological information.     

Reptiles from Len?óis Maranhenses National Park,Maranh?o,northeastern Brazil

We are presenting a list of the reptile species from Lençóis Maranhenses National Park (LMNP), Maranhão, Brazil, obtained during 235 days of field work. The study area is located in the contact zone between three major Neotropical ecosystems: Amazonia, Caatinga, and Cerrado. The PNLM encompasses the largest dune fields in Brazil, wide shrubby areas (restingas), lakes, mangroves, and many freshwater lagoons. We have recorded 42 species of reptiles in the area: 24 snakes, 12 lizards, two worm lizards, three turtles, and one alligator. About 81 % of the recorded species occurred only in restinga areas. Our data highlights the uniqueness of the PNLM in the context of the biomes that surround it and shows the importance of efforts to improve the conservation of reptiles living in the restinga, which currently comprise only about 20 % of the total area protected by the park, but which are the mesohabitat containing most of the reptile species in the Lençóis Maranhenses complex of habitats.     

Tikiguania and the antiquity of squamate reptiles (lizards and snakes)

Tikiguania estesi is widely accepted to be the earliest member of Squamata, the reptile group that includes lizards and snakes. It is based on a lower jaw from the Late Triassic of India, described as a primitive lizard related to agamids and chamaeleons. However, Tikiguania is almost indistinguishable from living agamids; a combined phylogenetic analysis of morphological and molecular data places it with draconines, a prominent component of the modern Asian herpetofauna. It is unlikely that living agamids have retained the Tikiguania morphotype unchanged for over 216 Myr; it is much more conceivable that Tikiguania is a Quaternary or Late Tertiary agamid that was preserved in sediments derived from the Triassic beds that have a broad superficial exposure. This removes the only fossil evidence for lizards in the Triassic. Studies that have employed Tikiguana for evolutionary, biogeographical and molecular dating inferences need to be reassessed.     

Extinction Risks and the Conservation of Madagascar's Reptiles

Background

An understanding of the conservation status of Madagascar''s endemic reptile species is needed to underpin conservation planning and priority setting in this global biodiversity hotspot, and to complement existing information on the island''s mammals, birds and amphibians. We report here on the first systematic assessment of the extinction risk of endemic and native non-marine Malagasy snakes, lizards, turtles and tortoises.

Methodology/Principal Findings

Species range maps from The IUCN Red List of Threatened Species were analysed to determine patterns in the distribution of threatened reptile species. These data, in addition to information on threats, were used to identify priority areas and actions for conservation. Thirty-nine percent of the data-sufficient Malagasy reptiles in our analyses are threatened with extinction. Areas in the north, west and south-east were identified as having more threatened species than expected and are therefore conservation priorities. Habitat degradation caused by wood harvesting and non-timber crops was the most pervasive threat. The direct removal of reptiles for international trade and human consumption threatened relatively few species, but were the primary threats for tortoises. Nine threatened reptile species are endemic to recently created protected areas.

Conclusions/Significance

With a few alarming exceptions, the threatened endemic reptiles of Madagascar occur within the national network of protected areas, including some taxa that are only found in new protected areas. Threats to these species, however, operate inside and outside protected area boundaries. This analysis has identified priority sites for reptile conservation and completes the conservation assessment of terrestrial vertebrates in Madagascar which will facilitate conservation planning, monitoring and wise-decision making. In sharp contrast with the amphibians, there is significant reptile diversity and regional endemism in the southern and western regions of Madagascar and this study highlights the importance of these arid regions to conserving the island''s biodiversity.     

Technics for blood collection and intravascular infusion of reptiles.

Several methods for external sampling of blood and administration of intravascular fluids are applicable to reptilian species. This paper reviewed some of the technics that have been previously reported and introduced several new procedures applicable to snakes, turtles, alligators, crocodiles, and lizards.