Friday, September 18, 2015

New taxonomic arrangement for the short-horned lizards of the douglasii Species Group

Members of the Phrynosma douglassi complex. Photo
 credit: R. Montanucci.
Horned Lizards of the genus Phrynosoma are perhaps the most novel North American lizards. One species group, the Short-horned lizards (the Phrynosoma douglasii species complex) occur throughout the inter-montane West and Great Plains of western North America. In a new paper, Montanucci (2015) has reviewed the taxonomy of these lizards, using comparative morphology and color pattern variation in 3,174 specimens.  Multivariate analyses of 20 morphological and color-pattern characters were applied to 977 specimens, and univariate statistics were summarized for 52 samples totaling 1,134 specimens. The results support the recognition of Phrynosoma douglasii (Bell 1828) as a distinct species, and the resurrection of P. brevirostris Girard 1858 and P. ornatissimum Girard 1858 as species distinct from Phrynosoma hernandesi Girard 1858.
Phrynosoma brevirostris is found in sagebrush and short-grass communities as well as in open canopy conifer savanna at higher elevations. Two new species allied to Phrynosoma brevirostris were described.  Phrynosoma bauri from the eastern plains of Colorado and northeastern New Mexico, southeastern Wyoming and southwestern Nebraska south of the North Platte River inhabits areas dominated by Grama-buffalo grass to Juniper-pinyon woodland, and Pine-Douglas fir. The second species allied to P. brevirostris is Phrynosoma diminutum, a species endemic to the San Luis Valley of southern Colorado and northern New Mexico. The Mexican taxon brachycercum Smith is reassigned as a subspecies of Phrynosoma ornatissimum. The ranges of Phrynosoma hernandesi and P. ornatissimum broadly overlap in central New Mexico, the former occupying the coniferous forests of disjunct mountain ranges, the latter occurring in the surrounding desert grasslands.
Principal components analysis suggests morphological evidence for hybridization where the two taxa meet, often within ecotones between montane forest associations and grasslands. Principal components analysis also revealed a high level of morphological variability in the Colorado Plateau region of northeastern Arizona, northwestern New Mexico, extreme southwestern Colorado and adjacent Utah. The evidence suggests that these populations arose through past hybridization between the two species.
The taxon ornatum Girard 1858, although sharing several traits with Phrynosoma brevirostris, is morphologically close to P. hernandesi. It is regarded as a stabilized population of hybrid origin, but treated as a subspecies of Phrynosoma hernandesi.
Phrynosoma douglasii inhabits Sagebrush steppe over much of the Columbia Plateau of eastern Washington based on museum records. It has been reported only from the sagebrush regions of southeastern Washington. The dense, low to medium tall grass may have precluded the establishment of short-horned lizard populations over much of this habitat, except where exposed, friable soils were present. In Oregon, populations east of the Cascades occur in Sagebrush steppe, but in the vicinities of Lake Abert and Fossil Lake, the lizards have also been collected in Saltbush-greasewood association. In the Cascade Range, populations occur in open conifer forest, including Silver fir-Douglas fir forest and Fir-hemlock forest on the western slopes, and Grand fir-Douglas fir forest, and Ponderosa shrub forest on the eastern slopes above the Sagebrush steppe.
 Phrynosoma douglasii inhabits open-canopy forests with widely spaced trees and well-drained, friable soils. Dense forests, with closed canopies, impede the establishment of populations. In southern Idaho, known localities are dominated by sagebrush steppe, and as yet, there are no confirmed records in Douglas fir forest and Western spruce-fir forest in the mountain ranges north of the Snake River Plain.
Phrynosoma h. hernandesi ranges from northern Sonora (recorded as far south as Sierra de la Madera) through the isolated mountain ranges and grasslands of southeastern Arizona northward along the Mogollon Rim. It ranges across the Coconino and Kaibab plateaus and follows the Wasatch Range in Utah. It occurs in the Pavant Range west of the Sevier River, and in the Henry Mountains northeast of the Escalante River, but presently there are no records from the Uinta Mountains in Utah. In northwestern Arizona there are records for the Hualapai and Cerbat mountains, Shivwits Plateau (near Snap Point) and the Mount Trumbull area.
The taxonomic arrangement in this study, with the exception of P. douglasii, is largely discordant with the proposed taxonomy from a previously published study based on mitochondrial DNA sequence data.

Citation

Montanucci, R. R. (2015). A taxonomic revision of the Phrynosoma douglasii species complex (Squamata: Phrynosomatidae). Zootaxa, 4015(1), 1-177.

Monday, September 14, 2015

South Florida and invasive herps

Iguana iguana is invasive in Florida
South Florida is on the front lines in the war against invasive reptiles and amphibians because its warm climate makes it a place where they like to live, a new University of Florida study shows.

Using computer models and data showing where reptiles live in Florida, UF/IFAS scientists predicted where they could find non-native species in the future. They found that as temperatures climb, areas grow more vulnerable to invasions by exotic reptiles. Conversely, they found that extreme cold temperatures protect against invasion.

"Early detection and rapid response efforts are essential to prevent more of the 140 introduced species from establishing breeding populations, and this study helps us choose where to look first," said Frank Mazzotti, a wildlife ecology and conservation professor at the University of Florida Institute of Food and Agricultural Sciences Fort Lauderdale Research and Education Center.

The new study is published online in the journal Herpetological Conservation Biology.

Lead author Ikuko Fujisaki, an assistant professor of wildlife ecology and conservation at the Fort Lauderdale REC, said scientists conducted the study to provide scientific data for managing invasive wildlife in the Sunshine State.

America imports more exotic animals than any other country in the world, with more than 1 billion animals entering the nation from 2005 through 2008, according to the U.S. Government Accountability Office. They come in by boats, planes and other modes of transportation. The animals are often used in the pet trade, but have other uses as well, including food and religious practices. Once they're established, exotic animals are costly to remove, according to a 2010 led by Michigan State University. Therefore, wildlife management agencies are always looking for better ways to detect the invasive species early.

Urban areas are hubs of international transport and therefore are major gateways for exotic pests. With its subtropical and tropical climates and its high human population (19.9 million as of 2014), Florida provides a unique opportunity for a geographic risk assessment because of the number of exotic species that establish, fail to establish or whose fate is unknown, the UF/IFAS scientists said.

Invasive species are second only to losing habitats in contributing to the loss of biodiversity worldwide, Mazzotti wrote in a 2015 UF/IFAS Extension paper. Florida has more introduced species of reptiles and amphibians in the wild than anywhere else in the world.

This data leads Mazzotti to suggest South Florida as the focal area for exotic species.

"We need to focus immediate management efforts on South Florida, or invasive wildlife could jeopardize Everglades restoration," Mazzotti said.

The authors add, "Since we created our list of target species, additional exotic herpetofaunal species have been introduced and become established in Florida. Some institutions in Florida, such as UFHerpetology, have been working toward accurately georeferencing occurrence locations in the state and make the data available online (https://www. flmnh.ufl.edu/herpetology/) or shared with other online databases such as GBIF and HerpNet (http://www.herpnet.org). Such data could be useful to further improve our predictions. Further, numerous imported exotic reptile species have not yet been observed in the wild but could be introduced through various pathways. Previous taxonomic risk assessments of exotic species have proposed various algorithms to predict potentially invasive species and have discussed their utility in invasive species management (Hayes and Barry 2008). Such assessments have been a part of the Australian national screening protocol for plants (Pheloung et al. 1999; Keller et al. 2007) and have been recommended for introduction as a part of invasive management practice in the United States (Lodge et al. 2006). Geographic assessments such as ours can be used to develop cost-effective management strategies by depicting spatial variability in habitat suitability for established, introduced, and imported species over wide geographic areas with variable environmental conditions.


Citation

Ikuko Fujisaki, Frank J. Mazzotti, James Watling, Kenneth L. Krysko, and Yesenia Escribano. Geographic Risk Assessment Reveals Spatial Variation in Invasion Potential of Exotic Reptiles in an Invasive Species Hotspot. Herpetological Conservation Biology, 2015; 10 (2): 621-632 

Wednesday, September 9, 2015

Eunotosaurus, and the origin of turtles

Eunotosaurus africanus (Seeley 1892) Middle Permian ~15 cm 
snout to vent length, was considered by Watson (1914) as the 
ancestor to the turtle because of its wide ribs and low number 
of dorsal vertebrae. The present study nests turtles with 
Stephanospondylus and the wide ribs find their origins in the 
less wide ribs of Milleretta RC14. Derived from a sister to
Acleistorhinus, Eunotosaurus left no known descendent taxa.

A research team led by NYIT scientist Gaberiel Bever has determined that a 260-million year-old fossil species found in South Africa's Karoo Basin provides a long awaited glimpse into the murky origins of turtles.

Bever, describes the extinct reptile, named Eunotosaurus africanus, as the earliest known branch of the turtle tree of life.

"Eunotosaurus is a critical link connecting modern turtles to their evolutionary past," said Bever, an assistant professor of anatomy at the NYIT College of Osteopathic Medicine. "This is the fossil for which science has been searching for more than 150 years. You can think of it as a turtle, before turtles had a shell."

While Eunotosaurus lacks the iconic turtle shell, its extremely wide ribs and distinctively circular torso are the first indications that this fossil represents an important clue in a long unsolved mystery: the origin of turtles. In a new study published in Nature, Bever and his colleagues from the Denver Museum of Nature and Science, Yale University, and the University of Chicago focus their attention on the skull of Eunotosaurus. Their findings indicated that the complex anatomy of the head houses convincing evidence of the important role played by Eunotosaurus in the deep history of turtle evolution.

"Our previous studies showed that Eunotosaurus possessed structures that likely represent the first steps in the evolution of the turtle shell" added Tyler Lyson of the Denver Museum of Science and Nature and a coauthor of the study, "but what those studies lacked was a detailed analysis of the skull."

Using high-resolution computed tomography, Bever digitally dissected the bones and internal structures of multiple Eunotosaurus skulls, all of which are housed in South African museums. He then incorporated his observations into a new analysis of the reptile tree of life. The process took the better part of four years, but according to Bever, the results were well worth the effort.

"Imaging technology gave us the opportunity to take the first look inside the skull of Eunotosaurus," said Bever, "and what we found not only illuminates the close relationship of Eunotosaurus to turtles, but also how turtles are related to other modern reptiles."

One of the study's key findings is that the skull of Eunotosaurus has a pair of openings set behind the eyes that allowed the jaw muscles to lengthen and flex during chewing. Known as the diapsid condition, this pair of openings is also found in lizards, snakes, crocodilians, and birds. The skull of modern turtles is anapsid -- without openings -- with the chamber housing the jaw muscles fully enclosed by bone.

The anapsid-diapsid distinction strongly influenced the long-held notion that turtles are the remnants of an ancient reptile lineage and not closely related to modern lizards, crocodiles, and birds. The new data from Eunotosaurus rejects this hypothesis.

"If turtles are closely related to the other living reptiles then we would expect the fossil record to produce early turtle relatives with diapsid skulls," said Bever. "That expectation remained unfulfilled for a long time, but with some help from technology and a lot of hard work on our part, we can now draw the well-supported and satisfying conclusion that Eunotosaurus is the diapsid turtle that earlier studies predicted would be discovered."

In linking turtles to their diapsid ancestry, the skull of Eunotosaurus also reveals how the evidence of that ancestry became obscured during later stages of turtle evolution.

"The skull of Eunotosaurus grows in such a way that its diapsid nature is obvious in juveniles but almost completely obscured in adults. If that same growth trajectory was accelerated in subsequent generations, then the original diapsid skull of the turtle ancestor would eventually be replaced by an anapsid skull, which is what we find in modern turtles."

Although the new study represents a major step towards understanding the reptile tree of life, Bever emphasizes that it will not be the final chapter in the science of turtle origins.

"The beauty of scientific discoveries is that they tend to reveal more questions than they answer" said Bever, "and there is still much we don't know about the origin of turtles. Which of the other diapsid groups form their closest cousin? What were the ecological conditions that led to the evolution of the turtle's shell and anapsid skull? And how much of the deep history of turtle evolution can be discovered by studying the genes and developmental pathway of modern turtles?"


Citation
G. S. Bever, Tyler R. Lyson, Daniel J. Field, Bhart-Anjan S. Bhullar. Evolutionary origin of the turtle skull. Nature, 2015; DOI: 10.1038/nature14900

Desmatochelys padillai, the oldest sea turtle

The skeleton of Desmatochelys padillai measures almost 2 meters.
Photo Credit:PaleoBios/Cadena

Scientists at the Senckenberg Research Institute in Frankfurt have described the world's oldest fossil sea turtle known to date. The fossilized reptile is at least 120 million years old -- which makes it about 25 million years older than the previously known oldest specimen. The almost completely preserved skeleton from the Cretaceous, with a length of nearly 2 meters, shows all of the characteristic traits of modern marine turtles. The study was published in the scientific journal PaleoBios.

"Santanachelys gaffneyi is the oldest known sea turtle" -- this sentence from the online encyclopedia Wikipedia is no longer up-to-date. "We described a fossil sea turtle from Colombia that is about 25 million years older," said Dr. Edwin Cadena, a scholar of the Alexander von Humboldt foundation at the Senckenberg Research Institute. Cadena made the unusual discovery together with his colleague from the US, J. Parham of California State University, Fullerton.

"The turtle described by us as Desmatochelys padillai sp. originates from Cretaceous sediments and is at least 120 million years old," says Cadena. Sea turtles descended from terrestrial and freshwater turtles that arose approximately 230 million years ago. During the Cretaceous period, they split into land and sea dwellers. Fossil evidence from this time period is very sparse, however, and the exact time of the split is difficult to verify. "This lends a special importance to every fossil discovery that can contribute to clarifying the phylogeny of the sea turtles," explains the turtle expert from Columbia.

The fossilized turtle shells and bones come from two sites near the community of Villa de Leyva in Colombia. The fossilized remains of the ancient reptiles were discovered and collected by hobby paleontologist Mary Luz Parra and her brothers Juan and Freddy Parra in the year 2007. Since then, they have been stored in the collections of the "Centro de Investigaciones Paleontológicas" in Villa Leyva and the "University of California Museum of Paleontology."

Cadena and his colleague examined the almost complete skeleton, four additional skulls and two partially preserved shells, and they placed the fossils in the turtle group Chelonioidea, based on various morphological characteristics. Turtles in this group dwell in tropical and subtropical oceans; among their representatives are the modern Hawksbill Turtle and the Green Sea Turtle of turtle soup fame.

"Based on the animals' morphology and the sediments they were found in, we are certain that we are indeed dealing with the oldest known fossil sea turtle," adds Cadena in summary.


Citation

Cadena, E.A. and J.F. Parham. Oldest known marine turtle? A new protostegid from the Lower Cretaceous of Colombia. PaleoBios, September 2015

Friday, September 4, 2015

The ancestral squamate was oviviparous ― I think

All members of the sand boa genus Eryx give birth to live young, except the 
Arabian Sand Boa, Eryx jayakari. This suggests that E. jayakari (left) 
re-evolved egg-laying from a viviparous ancestor. Right the viviparous Kenyan 
sand boa Eryx colubrinus.  Photo credits: Rick Staub and Arkive, and 
Roy Stockwell.
I very much dislike chicken and egg questions because it immediately sucks you into an argument with a creationist, most of whom simply don't get it. As Wright et al. (2015) point out the answer is clear from an evolutionary standpoint. The amniote egg, existed by the time the earliest amniotes (mammals and reptiles) diverged from one another about 325 million years ago, long before the first chicken (= birds) walked the Earth. Today, the majority of living amniotes are oviparous, including all birds, crocodylians, tuataras, turtles, and monotreme mammals. However, squamates are far more diverse in their approach to giving birth or laying eggs.
Approximately 20% of squamate species are viviparous, and this complex of traits has been estimated to evolve independently over 100 times across the squamate phylogeny. Viviparous species, developing embryos are retained in the mother's uterus for the entire duration of embryonic development. The traditional view of laying eggs or giving birth in amniotes is that the most recent common ancestor of squamates, which lived ~200 mya, was oviparous, as it inherited the same ancestral parity mode that characterizes all other reptiles.
The transition from oviparity to viviparity requires extensive modification of uterine physiology and morphology. For example, uterine shell glands in oviparous species secrete calcium during the discrete period of eggshell construction. In viviparous species, shell gland function has been modified to provide calcium to the embryo throughout gestation. True “ovoviviparity” does not exist in squamates, as all examined viviparous squamates have some form of placenta composed of both maternal and embryonic tissue.
The uterine structure of oviparous species is, therefore, modified into the maternal half of the placenta in viviparous species. The embryonic portion of the placenta is composed from the same extra-embryonic membranes that are present in all amniote eggs. Most squamate placentae are relatively simple structures used primarily for gas exchange and water transport, but a more elaborate placenta that facilitates significant nutrient exchange has evolved at least six times in squamates. Underlying the evolutionary transition to viviparity and a placenta are significant changes in gene expression of hundreds of genes.
In a new paper Wright et al. (2015) re-evaluate support for the provocative idea that the first squamates were viviparous. They test the sensitivity of the analysis to model assumptions and estimates of squamate phylogeny. They found that the models and methods used for parity mode reconstruction are highly sensitive to the specific estimate of phylogeny used, and that the point estimate of phylogeny used to suggest that viviparity is the root state of the squamate tree is far from an optimal phylogenetic solution.
The ancestral state reconstructions are also highly sensitive to model choice and specific values of model parameters. A method that is designed to account for biases in taxon sampling actually accentuates, rather than lessens, those biases with respect to ancestral state reconstructions. In contrast to recent conclusions from the same data set, Wright et al. (2015) found that ancestral state reconstruction analyses provide highly equivocal support for the number and direction of transitions between oviparity and viviparity in squamates. Moreover, the reconstructions of the ancestral parity state are highly dependent on the assumptions of each model. The authors conclude that the common ancestor of squamates was oviparous, and subsequent evolutionary transitions to viviparity were common, but reversals to oviparity were rare. The three putative reversals to oviparity with the strongest phylogenetic support occurred in the snakes Eryx jayakari and Lachesis, and the lizard, Liolaemus calchaqui. The authors emphasize that because the conclusions of ancestral state reconstruction studies are often highly sensitive to the methods and assumptions of analysis, researchers should carefully consider this sensitivity when evaluating alternative hypotheses of character-state evolution.

Citation

Wright AM, Lyons KM, Brandley MC, Hillis DM. 2015. Which came first: the lizard or the egg? Robustness in phylogenetic reconstruction of ancestral states. Journal of Experimental Zoology (Mol. Dev. Evol.) 324B:504–516.

Tuesday, September 1, 2015

When sister species live together, Tegu lizards in Argentina


Two Tegus, Salvator merianae and S. rufescens JCM
When two closely related species live side by side it is generally assumed that they have some way of dividing the resources so that they are not in direct competition with each other. The large terrestrial lizards the Black and White Tegu, Tupinambis (=Salavator) merianae, and the Red Tegu, T. (=Salvator) rufescens provide a model system to examine the role of life history factors in trophic niche divergence because they share several bioecological traits. They have similar body sizes and share external morphology and generalized foraging habits. Phylogenetic studies suggest the two species are sisters. In Argentina, they occur in parallel allopatric zones from approximately 10–40°S. Tupinambis rufescens occurs further west than T. merianae. However, they both occupy a large contact zone. These species differ in habitat requirements in allopatric areas, but in the contact zone the species use the same landscape and habitat resources. Moreover, T. merianae and T. rufescens select landscapes with a large proportion of forest and shrubs than the mean landscape availability in contact zones.

In a new paper López Juri et al. (2015) evaluate the trophic niche segregation between merianae and rufescens in a contact zone to understand how life history traits (body size, sexual body size dimorphism, sexual maturity and reproductive activity) might influence the feeding ecology of these lizards and lead to trophic niche differentiation between species. Their results suggest that, although both species are omnivorous, they exhibit a tendency to specialize, with arthropods being dominant in the diet of merianae and fruits and seeds being dominate in the diet of rufescens. The two species have broad trophic overlap, however, while both species share several prey items, the relative importance of each item varied between them. These differences may be important for niche segregation, mainly because the prey items considered fundamental were different between species, suggesting a differential use of certain resources. T. merianae is often associated with anthropogenic areas with cultural vegetation and remnant shrub lands where few vertebrate species remain which may explain the low diversity of food items and the dominance of arthropods and some rodents in the diet composition. Their results indicate that body size, sexual maturity and reproductive activity are relevant factors influencing the diet of these species. Life history traits of these two species of Tupinambis are important because they shape diet composition, contributing to interspecific segregation of the trophic niche and, therefore, allowing species coexistence.

Citation

López Juri G, Naretto S, Mateos AC, Chiaraviglio M, Cardozo G. 2015. Influence of life history traits on trophic niche segregation between two similar sympatric Tupinambis lizards. South American Journal of Herpetology, 10(2): 132–142.

The coral snake & the caecilian


Photo credit: DMM Mendes
The majority of coral snakes are terrestrial/fossorial species, but the Suriname Coral Snake (Micrurus surinamensis) and the Ribbon Coral Snake (Micrurus lemniscatus) use shallow water, swampy habitats for foraging for food. Like other coral snakes they tend to feed on small, elongated prey. Their diet includes invertebrates, lizards, amphibians, fish, and other snakes. The Ribbon Coral Snake (Micrurus lemniscatus) is a known predator of caecilians, amphisbaenians, and blind snakes. In a recent note Viana and de Mello Mendes (2015) document the first recorded predation of the two-lined caecilian, Rhinatrema bivittatum, in central Amazon. The snake bit the caecilian at mid-body, held on to it for about five minutes (probably to inject venom). The snake then released the prey and crawled to a sheltered site about 30 cm away. After five minutes the snake returned to the caecilian struck it several times with little response from the amphibian, the coral snake then ingested the prey.

Photos by DMM Mendes

Monday, August 31, 2015

Digestive system's adaptations to island life in Lacerta trilineata


Balkan Green Lizard. Lacerta trilineata.Photo Credit: 
Kostas Sagonas
Life on an island isn't always easy. To make the most of the little there is to eat on many Greek islands, the digestive system of s has evolved considerably compared to family members on the mainland. Surprisingly, many of these insect-eating lizards even have special valves that help to digest plants. These are some of the findings¹ from a study led by Konstantinos Sagonas of the National and Kapodistrian University of Athens in Greece, published in Springer's journal The Science of Nature².
Reptiles can adjust their digestive system and food preferences due to adverse circumstances such as low rainfall and poor food supply. Previous studies, for instance, show that insect-eating Balkan green lizards (Lacerta trilineata) surviving in the harsh environments of various Greek islands have broadened their diet to include more plants. To extend this research, Sagonas' team set out to compare groups of these lizards on the islands of Andros and Skyros with two other populations in mainland Greece.
They found that the island lizards have a longer small intestine and hindgut compared to their mainland counterparts. Those collected from the island of Skyros also have larger stomachs. When the animals were dissected, the researchers made an unusual discovery. Cecal valves, which slow down food passage and provide fermenting chambers, were found in 62 percent of the island-dwelling lizards, compared to 19 percent of the mainland ones. This was a fact not previously known for green lizards.
Cecal valves are typically found in plant-eating lizards, and host micro-organisms that help to ferment and break down plant material into fatty acids.. When these structures do occur in insect-eating lizards, it is generally among populations that have started to eat a varied diet that also includes plants. Sagonas believes the presence of cecal valves among the island lizards therefore reflects their higher consumption of plant material. About 30 percent of their diet consists of plant material, compared to the 10 percent of the mainland reptiles.
Their evolved digestive system therefore makes it possible for island lizards to eat more plants. Because of their longer digestive tract and the presence of cecal valves, it takes up to 26 percent longer for the food of island lizards to pass through their digestive system. In a process which is more common to plant-eating lizards, the ingested food is ultimately exposed far longer to digestive enzymes.
"Such adaptations allow insular populations to take advantage of the limited food resources of the islands and, eventually, overcome food dearth," explains Sagonas. "Energy flow in insular environments, the digestive performance of insular populations and the connections within them, provide insights into how animals are able to colonize islands and maintain viable populations." 


Citation

Sagonas K, Pafilis P., Valakos ED. Effects of insularity on digestion: living on islands induces shifts in physiological and morphological traits in island reptilesThe Science of Nature, 2015; 102 (9-10) DOI: 10.1007/s00114-015-1301-8

Saturday, August 29, 2015

A model for managing the Giant Garter Snake, Thamnophis gigas

Thamnophis gigas. Photo by Dave Feliz
The Giant Gartersnake (Thamnophis gigas) is a highly aquatic species that uses marshes and sloughs, low-gradient streams, ponds, and small lakes, with cattails, bulrushes, willows, or other emergent or water-edge vegetation. Because of the direct loss of natural habitat, this snake now relies heavily on rice fields in the Sacramento Valley, but it also uses managed marsh areas in various national wildlife refuges and state wildlife areas. Essential habitat components consist of adequate water during the snake's active season (early spring through mid-fall) to provide adequate permanent water to maintain dense populations of food organisms; emergent, herbaceous wetland vegetation, such as cattails and bulrushes, for escape cover and foraging habitat during the active season; upland habitat with grassy banks and openings in waterside vegetation for basking; and  higher elevation upland habitats for cover and refuge from flood waters during the snake's inactive season in the winter. The Giant Garter Snake is absent from large rivers and other waters with populations of large, introduced, predatory fishes, and from wetlands with sand, gravel, or rock substrates. Riparian woodlands do not provide suitable habitat because of excessive shade and inadequate prey resources. As of 1992, there were 13 known populations. Not all of have good viability. The adult population size is unknown but presumably is at least a few thousand. Estimates of population size for three local populations in the mid-1990s were in the low 100's. The species is now apparently extirpated or very rare in most of the former range in the San Joaquin Valley. Surveys in the 1970s and 1980s yielded some previously unknown localities and several cases of extirpation or at least severe population declines. The area of occupancy, number of subpopulations, and population size are probably continuing to decline, but the rate of decline is unknown.
 Because more than 90 percent of their historical wetland habitat has been converted to other uses, the species has been listed as threatened by the State of California (California Department of Fish and Game Commission, 1971) and the United States (U.S. Fish and Wildlife Service, 1993). Giant Gartersnakes inhabit a highly modified landscape, with most extant populations occurring in the rice-growing regions of the Sacramento Valley, especially near areas that historically were tule marsh habitat. In ricelands and managed marshes, many operational decisions likely impact the health and viability of Giant Gartersnake populations. Land-use decisions, including the management of water, aquatic vegetation, terrestrial vegetation, and co-occurring species, have the potential to affect giant Gartersnake populations. Little is known, however, about the effects of these types of decisions on the viability of the populations.
In a recent report Halstead et al. (2015) recognized that Bayesian network models are a useful tool to help guide decisions with uncertain outcomes. These models require the articulation of what experts think they know about a system, and facilitate learning about the hypothesized relations. Bayesian networks further provide a clear visual display of the model that facilitates understanding among various stakeholders. Empirical data and expert judgment can be combined, as continuous or categorical variables, to update knowledge about the system. The objective of this project was to develop a conceptual model of site-specific ecology of the Giant Gartersnake in the Sacramento Valley of California. The authors chose to develop the model at a site-specific scale because that is the scale at which most management decisions are made and at which Giant Gartersnake responses can be quantified. They used a Bayesian network model, and also quantified uncertainty associated with different nodes affecting ecology of the Giant Gartersnake, and the strength of influence of different variables on population growth rates of the species. This is a preliminary step in an ongoing process to clarify and quantify the effects of management actions on Giant Gartersnake populations.
They found population growth of the Giant Gartersnake was most influenced by demographic parameters, especially adult survival. Directly managing for increased survival or fecundity, however, generally is not feasible. Habitat quality, was strongly influenced by water availability and emergent vegetation and had a strong influence on both adult and first-year survival. Additional research into the effects of specific habitat attributes on Giant Gartersnake fitness is needed to better quantify the qualitative relations hypothesized in the Bayesian network model. In this regard, habitat quality; predator, parasite, and pathogen effects; and prey availability (particularly as it affects fecundity) all would be productive avenues for future research efforts. Alternatively, research could focus on those nodes for which the least information exists. For example, the scenario analysis indicated that changing Giant Gartersnake population growth from increasing to decreasing resulted in little change in many nodes. Competitor effects, other sources of mortality, and nearly all parents of habitat quality were changed little under increasing and decreasing population growth scenarios. This indicates that these variables either are truly unimportant for determining Giant Gartersnake population growth, or uncertainty in the strength of these relations precludes drawing conclusions about how these variables affect population growth of the Giant Gartersnake. The prudent course of action would be to conduct research into the effects of these variables on Giant Gartersnakes to determine which of these alternatives is correct.

Citation

Halstead, B.J., Wylie, G.D., Casazza, M.L., Hansen, E.C., Scherer, R.D., and Patterson, L.C., 2015, A conceptual model for site-level ecology of the giant gartersnake (Thamnophis gigas) in the Sacramento Valley, California: U.S.Geological Survey Open-File Report 2015-1152, 152 p., http://dx.doi.org/10.3133/ofr20151152.

Friday, August 28, 2015

A reassessment of the conservation status of the Central American herpetofauna

Salamanders like this Costa Rican Bolitoglossa striata are 
more susceptible to environmental disturbances than other
amphibians. JCM
A recently published article by Johnson et al. (2015) takes a second look at the herpetofauna of Central America and its conservation needs. The authors found Mesoamerica (the area composed of Mexico and Central America) is the third largest biodiversity hotspot in the world. The Central American herpetofauna has 493 species of amphibians and 559 species of crocodilians, squamates, and turtles.
The authors use a revised EVS measure to reexamine the conservation status of the herpetofauna using the General Lineage Concept of Species to recognize species-level taxa, and employ phylogenetic concepts to determine evolutionary relationships among the taxa.
Since the publication of Conservation of Mesoamerican Amphibians and Reptiles, in 2010, 92 species of amphibians and squamates have been described, resurrected, or elevated from subspecies to species level, and one species of anuran has been synonymized. The herpetofaunal diversity of Central America is comparable to that of Mexico, a significant finding because the land area of Mexico is 3.75 times larger. The number of amphibian species is 1.3 times greater in Central America, whereas the number of species of turtles, crocodilians, and squamates is 1.5 times greater in Mexico. Endemicity is also significant in Central America (65.6% of amphibians, 46.5% of turtles, crocodilians, and squamates), with a combined average of 55.6%.
The authors regard the IUCN system as expensive, time-consuming, and behind advances in systematics and over-dependent on the Data Deficient and Least Concern categories. Conversely, the EVS measure is economical, it can be applied when species are described, is predictive, simple to calculate, and does not “penalize” poorly known species.
The EVS analysis of amphibians demonstrates that on average salamanders are more susceptible to environmental deterioration, followed by caecilians, and anurans. Among the remainder of the herpetofauna, crocodilians are the most susceptible and snakes the least, with turtles and lizards in between.
Biodiversity decline is an environmental problem of global dimensions, comparable to the more commonly publicized problem of climate change. Both of these environmental super-problems exist because of human action and inaction, exacerbated by humanity’s anthropocentric focus.

Citation

Johnson, J. D., Mata-Silva, V., & Wilson, L. D. (2015). A conservation reassessment of the Central American herpetofauna based on the EVS measure. Amphibian & Reptile Conservation, 9(2), 1-94.

Wednesday, August 26, 2015

Gueragama sulamericana a Late Cretaceous stem iguanid from southern Brazil


Gueragama sulamerica. Credit: Julius Csotonyi
University of Alberta paleontologists have discovered a new species of lizard, named Gueragama sulamericana, in the municipality of Cruzeiro do Oeste in Southern Brazil in the rock outcrops of a Late Cretaceous desert, dated approximately 80 million years ago.

"The roughly 1700 species of iguanas are almost without exception restricted to the New World, primarily the Southern United States down to the tip of South America," says Michael Caldwell, biological sciences professor from the University of Alberta and one of the study's authors. Oddly however, iguanas closest relatives, including chameleons and bearded dragons, are all Old World. As one of the most diverse groups of extant lizards, spanning from acrodontan iguanians (meaning the teeth are fused to the top of their jaws) dominating the Old World to non-acrodontans in the New World, this new lizard species is the first acrodontan found in South America, suggesting both groups of ancient iguanians achieved a worldwide distribution before the final break up of Pangaea.

"This fossil is an 80 million year old specimen of an acrodontan in the New World," explains Caldwell. "It's a missing link in the sense of the paleobiogeography and possibly the origins of the group, so it's pretty good evidence to suggest that back in the lower part of the Cretaceous, the southern part of Pangaea was still a kind of single continental chunk."

Distributions of plants and animals from the Late Cretaceous reflect the ancestry of Pangaea when it was whole. "This Gueragama sulamericana fossil indicates that the group is old, that it's probably Southern Pangaean in its origin, and that after the break up, the acrodontans and chameleon group dominated in the Old World, and the iguanid side arose out of this acrodontan lineage that was left alone on South America," says Caldwell. "South America remained isolated until about 5 million years ago. That's when it bumps into North America, and we see this exchange of organism north and south. It was kind of like a floating Noah's Arc for a very long time, about 100 million years. This is an Old World lizard in the new world at a time when we weren't expecting to find it. It answers a few questions about iguanid lizards and their origin."

The University of Alberta is a world leader in paleontology. This study was a collaboration between the University of Alberta and scientists in Brazil. Caldwell says of the collaboration, "It's providing an opportunity for our students and research groups to expand our expertise and interests into an ever-increasing diversity of organisms within this group of animals called snakes and lizards."

The lead author of the paper is Caldwell's PhD student, Tiago Simoes, a Vanier scholar. "As with many other scientific findings, this one raises a number of questions we haven't previously considered," says Simoes. "This finding raises a number of biogeographic and faunal turnover questions of great interest to both paleontologists and herpetologists that we hope to answer in the future."

In terms of next steps, Caldwell notes "Each answer only rattles the questions harder. The evolution of the group is much older than has been previously thought, which means we can push an acrodontan to 80 million years in South America. We now need to focus on much older units of rock if we're going to find the next step in the process."

The findings, "A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana," were published in the journal Nature Communications, one of the world's top multidisciplinary scientific journals.

Citation

Tiago R. Simões, Everton Wilner, Michael W. Caldwell, Luiz C. Weinschütz, Alexander W. A. Kellner. A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana. Nature Communications, 2015; 6: 8149 DOI: 10.1038/ncomms9149

Wednesday, August 19, 2015

Embryonic lizards may not survive global warming

Currently, three percent of land in the US is inhospitable to 
lizards (orange areas). In the next century, the scientists say 
the areas where lizards may not thrive could grow to 48 
percent (purple area). Map Credit: Ofir Levy; Lizard Photo
 - The Tree Lizard, Urosaurus ornatus. JCM
The expected impact of climate change on North American lizards is much worse than first thought. A team of biologists led by Arizona State University investigators has discovered that lizard embryos die when subjected to a temperature of 110 degrees Fahrenheit even for a few minutes.

The researchers also discovered a bias in previous studies, which ignored early life stages such as embryos. Embryonic lizards are immobile and cannot seek shade or cool off when their surrounding soil becomes hot.

This bias produced overly optimistic forecasts about the fate of lizards during climate change. Given the potential impacts on embryos, many more places in the United States could become uninhabitable for lizards than previously expected.

"Lizards put all of their eggs in one basket, so a single heat wave can kill an entire group of eggs," said Ofir Levy, lead investigator of the study and postdoctoral fellow with ASU School of Life Sciences. "If mothers don't dig deeper nests to lay their eggs, we expect this species to decline throughout the United States."

The findings appear today online in the journal Proceedings of the Royal Society B.

After finding that lizard embryos cannot tolerate 110 degrees Fahrenheit for even a short period, the researchers used a climate model to predict how often heat waves in the past and future would kill developing lizards. Areas in the U.S. reaching lethal temperatures, even in the shade, could spread from 3 percent currently to 48 percent of the country in the next century.

Female lizards lay eggs in spring and summer, digging nests and then leaving their offspring to develop for more than two months. Mothers may choose shadier soils or dig deeper nests to help their offspring avoid the heat. But even if lizards lay eggs in cooler places, nests may still exceed the temperatures that embryonic lizards can tolerate. And, assuming that baby lizards could reach the surface after hatching from a deeper nest, that still may not offer enough protection. Repeated exposure to above average, but not lethal temperatures, can negatively affect a lizard's physiology and behavior.

"Since this year promises to be the hottest on record, we are asking whether organisms, like lizards, can adjust to their warming world," said Michael Angilletta, professor and senior sustainability scientist with ASU School of Life Sciences. "It's critical that we acquire detailed knowledge about what temperatures these lizards and other animals can tolerate throughout the life cycle, not just as adults."

Levy added: "Because lizards are prey for animals such as birds, snakes and mammals, the harmful effects of climate change on embryonic lizards could also negatively affect other species."

Citation
Levy O,  Buckley LB,  Keitt TH,  Smith CD, Boateng KO, Kumar DS,  Angilletta MJ. 2015. Resolving the life cycle alters expected impacts of climate change. Proceedings of the Royal Society B, August  DOI: 10.1098/rspb.2015.0837

Thursday, August 13, 2015

New book: Atlas Serpientes de Venezuela - Price Reduced


Atlas Serpientes de Venezuela by Marco Natera Mumaw, Luis Felipe Esqueda, González and Manuel. The book's size is 32x25, full color, dust jacket, it contains 456 pages,>400 photos, >60 maps on geographic distribution and assembled in four chapters and four thematic appendices. For requests send an email to Luis Felipe Esqueda, Co-author and Editor or directly to Marisol Diaz Astorga (responsible for final acceptance and shipping, see instructions). General cost of book is 60$ + 10$ PayPal or Western Union (charges a commission) + shipping costs depending on the location (certified by Correos de Chile).









Friday, August 7, 2015

Venomous frogs


Corythomantis greeningi greening was found to have spines extending from  its skull that can poke through the skin to deliver poison into potential predators (left). Corythomantis greeningi greening, or Greening's frog (middle). Aparasphenodon brunoi, or Bruno's Casque-headed Frog (right.).
Photo Credit: Carlos Jared.

Venomous animals have toxins associated with delivery mechanisms that can introduce the toxins into another animal.

Although most amphibian species produce or sequester noxious or toxic secretions in the glands of the skin to use as antipredator mechanisms, they have been considered poisonous rather than venomous because delivery mechanisms are absent.

The frogs in question – the Greening’s frog (Corythomantis greeningi) and the Bruno’s casque-headed frog (Aparasphenodon brunoi) – produce potent toxins and also have a mechanism to deliver those harmful secretions into another animal using bony spines on their heads.

“Discovering a truly venomous frog is nothing any of us expected, and finding frogs with skin secretions more venomous than those of the deadly pit vipers of the genus Bothrops was astounding,” said  Edmund Brodie, Jr. from Utah State University, a team member and a co-author on the study.

The Greening’s frog and the Bruno’s casque-headed frog have both been known for many decades, if not centuries. But scientists have known little of their biology.

The team’s calculations suggest that a single gram of the toxic secretion from the Bruno’s casque-headed frog would be enough to kill more than 300,000 mice or about 80 humans.

“It is unlikely that a frog of this species produces this much toxin, and only very small amounts would be transferred by the spines into a wound. Regardless, we have been unwilling to test this by allowing a frog to jab us with its spines,” said lead author Dr Carlos Jared from the Instituto Butantan in São Paulo, Brazil.

The researchers, whose findings are published in the journal Current Biology, only discovered they were venomous while collecting amphibians for study. Jared was injured by a spine from Corythoimantis greeingi while handling it, leading to intense spreading pain in his hand for around five hours. Fortunately for him, the frog was the less toxic of the two. He said: 'The action should be even more effective on the mouth lining of an attacking predator.'

The researchers say they have still to find out exactly how much toxin the frogs can deliver in one go. However, they believe there may be other species of frog that are also venomous. Dr Brodie added: 'It is unlikely that a frog of this species produces this much toxin, and only very small amounts would be transferred by the spines into a wound. 'Regardless, we have been unwilling to test this by allowing a frog to jab us with its spines.'

“The new discovery is important for understanding the biology of amphibians and their interactions with predators in the wild,” the scientists said.

Citation
Jared et al. 2015. Venomous Frogs Use Heads as Weapons. Current Biology, doi: 10.1016/j.cub.2015.06.061

Wednesday, August 5, 2015

Snakes & Palm Oil Plantations in Colombia

The most commonly encountered snake in oil palm plantations
was Ninia atrata.
Rainforest in the tropics is frequent cut to make way for the African oil palms, Elaeis guineensis. The plant is most often grown for cooking oil but has recently attracted the attention of the alternative energy industry as a source of biofuel. While the plant is native to sub-Saharan Africa, it has now spread to tropical Asia and the Neotropics.
Lynch (2015) analyzes the snake species found during student field trips to Colombian oil palm plantations between 2006-2013. They visited 30 palm plantations varying in size from 0.02-20,000 hectares. These include small privately held palm trees groves as well as large commercial plantations. Success-rates varied with less success in the dry season and greater success in the wet season. Thirty-five snake species were found. Widespread lowland species (Boa constrictor, Clelia clelia, Corallus hortulanus, Imantodes cenchoa, Leptophis ahaetulla, Ninia atrata, Oxyrhopus petola, Tantilla melanocephala, and the species pairs of Bothrops asper or B. atrox, Epicrates cenchria or E. maurus, and Leptodeira annulata or L. septentrionalis). Seven other species (Chironius carinatus, Erythrolamprus bizona, Lampropeltis cf. triangulum, Mastigodryas boddaertii, M. pleei, Sibon nebulata, and Typhlops reticulatus) occur across the regions sampled but do not occupy all lowlands of Colombia. All of these except Imantodes cenchoa, Lampropeltis cf. triangulum, and Sibon nebulata were captured in at least one plantation. Of the 35 species of snakes captured in palm trees, fourteen were diurnal activity or crepuscular, the remaining 21 species are exclusively nocturnal.
To date, there are no reliable data on population sizes of any snake species in Colombia. In point of fact, the impression of collectors is that densities are very low. This impressions is contradicted by our work in palm plantations. Collecting in natural habitats by other researchers has produced success rates equivalent or superior to our work in palm trees.
The Colombian African palm oil industry could be a major factor in conserving snakes. Snake mortality from rural workers exceeds 100 million/year and no fewer than 50,000 snakes die/year due to traffic. However, to be a partner in snake conservation will require two changes in the industry: (1) all waste be fronds need to be piled into mounds on the plantation and allowed to decompose slowly. This provides refuges for snakes, easy access to prey, and reduces human encounters, Secondly, stop converting parcels of secondary forest into more monoculture of palms. Leaving patches of secondary forest and scrub increases microhabitats and the prey base.

Citation
Lynch, J. D. (2015). The role of plantations of the African palm (Elaeis guineensis Jacq.) in the conservation of snakes in Colombia. Caldasia, 37(1), 169-182.