Thursday, June 26, 2014

Invasive Nerodia in California

Southern water snakes commonly eat mole salamanders,
 a group that includes two endangered species in
California. (Photo credit: J.D. Willson/University of Arkansas)
Water snakes, commonly seen in the lakes, rivers and streams of the eastern United States, are invading California waterways and may pose a threat to native and endangered species in the state, according to a University of California, Davis, study.

While scientists do not know exactly how many water snakes are in California, roughly 300 individuals of two different species — the common water snake and the southern water snake — have been found in the Sacramento area (Roseville and Folsom), and at least 150 were seen in Long Beach. Researchers suspect the nonvenomous snakes most likely were introduced by people “setting free” their pet snakes.

“The issue is not yet out of control,” said lead author Jonathan Rose, a doctoral candidate in the UC Davis Graduate Group in Ecology. “However, we recommend that action be taken now to control emergent populations of these nonnative snakes while they remain somewhat restricted in California. Waiting until they become entrenched could cost more ecologically and economically.”

The study, published today in the journal PLOS ONE, identified areas that would be climatically suitable for the water snakes should their populations continue to increase. It found that potential distributions of water snakes overlap with the giant garter snake and the California tiger salamander — both on the federal list of threatened species -- as well as the foothill yellow-legged frog, an amphibian of conservation concern. These native species can become prey or a competing species for the invasive water snakes.

The common water snake not only has the potential to spread through Central California, but also farther north to Oregon’s Willamette Valley and to central Washington. The southern water snake has a more restricted climatic niche but may spread through the Central Valley, where native fish and amphibians have already suffered significant declines. The two water snake species also frequently interbreed, which could increase their invasiveness by producing hybrid genotypes able to tolerate a broader range of climates.

“Water snakes are not picky eaters,” said co-author Brian Todd, a conservation biologist in the UC Davis Department of Wildlife, Fish and Conservation Biology. “With their predatory nature and generalist diets, our already imperiled native fish, amphibians and reptiles have much to lose should introduced water snakes become more widespread.”

Nearly half of California’s amphibians are considered Species of Special Concern or are listed under the state or federal Endangered Species Act, and more than 80 percent of the state’s inland fishes are of conservation concern.

Sightings of introduced water snakes can be reported via email.

Citatiom
Rose JP, Todd BD (2014) Projecting Invasion Risk of Non-Native Watersnakes (Nerodia fasciata and Nerodia sipedon) in the Western United States. PLoS ONE 9(6): e100277. DOI: 10.1371/journal.pone.0100277

Thursday, June 19, 2014

Kirtland's snake subject of lawsuit

Photo by James Harding
CHICAGO The Center for Biological Diversity filed a lawsuit against the U.S. Fish and Wildlife Service today over the agency’s failure to grant Endangered Species Act protection to the Kirtland’s snake. The rare snake, now found only in scattered populations in the north-central Midwest, has sharply declined due to the loss of its prairie wetland habitat.
“Time is quickly running out for this rare reptile,” said Collette Adkins Giese, a Center lawyer and biologist who works to save imperiled amphibians and reptiles. “With protection of the Endangered Species Act, the snake would benefit from greater emphasis on saving its vanishing wetland habitats, which are also important for humans because they prevent floods and filter surface water.”

The Kirtland’s snake was once known from more than 100 counties in eight states. Since 1980 it has been observed in only a quarter of those counties. The current distribution of this snake is centered in metropolitan areas in Michigan, Ohio, Illinois, Indiana and Kentucky. It is often found in vacant lots associated with streams or wetlands in remnants of much larger populations that have been reduced by urbanization and are rapidly dying out.

“There’s broad scientific consensus that amphibians and reptiles are in the midst of a profound, human-driven extinction crisis that requires prompt action,” said Adkins Giese. “And the Kirtland’s snake simply can’t afford any more delay in receiving the protections of the Endangered Species Act, America’s most powerful law for saving species and putting them on the road to recovery.”

In 2010 the Center and its allies petitioned for Endangered Species Act protection for the Kirtland’s snake, as well as hundreds of other southeastern aquatic species. In 2011 the Fish and Wildlife Service determined that the snake “may warrant” protection as an endangered species, but it has failed to make the required finding on whether to give the animal federal protection.

The Kirtland’s snake Clonophis kirtlandi is a small, nonpoisonous snake that feeds on earthworms, slugs and leeches. It is state-listed as endangered in Indiana, Michigan and Pennsylvania (last recorded in 1965), and threatened in lllinois and Ohio. Historically most of the snake’s habitat has been lost to agricultural land use, but as urban and suburban sprawl continue to encroach on formerly undeveloped lands, residential development has become a substantial driver the snake’s decline. Collection for the pet trade poses another threat to many populations.

The Kirtland’s snake is one of 10 species across the country that the Center is prioritizing for Endangered Species Act protection this fiscal year. Under a settlement agreement with the Service that expedites protection decisions for 757 species, the Center can push forward 10 decisions per year. The other priority species for 2014 include the Alexander Archipelago wolf from Alaska, the San Bernardino flying squirrel, the Ichetucknee siltsnail from Florida, the black-backed woodpecker from California and South Dakota, and four freshwater species from the southeastern United States including two fish, a mussel and a crayfish. The species are facing extinction for many reasons, chief among them habitat loss from logging and development, global climate change, pollution, groundwater decline and water overuse. 


Under the landmark settlement 118 species have already gained Endangered Species Act protection, and another 24 have been proposed for protection.

Saturday, June 14, 2014

Snakes mimic extripated species to avoid predators

Left to right. This scarlet kingsnake could be easily mistaken for its venomous relative (Photo credit David Pfennig) Middle. A venomous coral snake from Florida (Florida Images/Alamy). Right. Scarlet kingsnakes living in the North Carolina Sandhills have fine-tuned their mimicry of coral snakes, even though — or perhaps because — coral snakes have become extinct in the area (Photo credit Wayne Van Devender).
An article in Nature News by Ewen Callway discusses North Carolina scarlet kingsnakes evolving in North Carolina to more closely resemble the eastern coral snake, a species no longer found in the area.

Scarlet kingsnakes are chasing an evolutionary ghost. In North Carolina's Sandhills forest, the harmless snakes have evolved to better resemble a poisonous species that vanished from the region more than 50 years ago.

The scarlet kingsnake, Lampropeltis elapsoides, copies the stripe patterns of deadly coral snakes, Micrurus fulvius, so well that people use mnemonic rhymes to tell them apart, such as: “If red touches yellow, you’re a dead fellow; if red touches black, you’re all right, Jack.” The species live side by side across much of southeastern North America. The scarlet kingsnake uses mimicry to dupe predators, such as red-tailed hawks, keen to avoid attacking the venomous reptile.

The Sandhills, a pine and oak forest in the eastern Carolinas, were once home to both snakes, but coral snakes disappeared from the area in the 1960s, says Chris Akcali, an evolutionary biologist at the University of North Carolina in Chapel Hill. He and his colleague David Pfennig are interested in how biological mimicry evolves, and they wondered whether the extinction of coral snakes would influence the colour patterns of scarlet kingsnakes.

To find out, Akcali and Pfennig compared scarlet kingsnakes from the Sandhills collected over the 40 years after coral snakes went extinct, and compared them to kingsnakes from the Florida panhandle, where coral snakes still slither. They expected that the Sandhills scarlet kingsnakes would have started evolutionarily drifting and looking less and less like coral snakes.

“When I went and collected the data, I looked at it and said, ‘This can’t be’,” Akcali says. The kingsnakes from the Sandhills that were collected in recent years tended to more closely resemble coral snakes — with red and black bands more similar in size — than did snakes collected in the 1970s, which tended to have larger black bands. He and Pfennig detected no such change in the Florida panhandle snakes over the same period. They report their results today in Biology Letters1.

The result makes sense, Akcali says. “If you are a predator, and you’re in an area like Florida, where coral snakes are everywhere, then you should avoid anything that looks like a coral snake,” he says. “If you are in North Carolina where coral snakes are really, really rare, predators can benefit from attacking [mimics] sometimes.”

Scarlet kingsnakes in the Sandhills should eventually stop resembling coral snakes, Akcali predicts. “Presumably, at some point predators are going to act as if there are no coral snakes, and they should attack them indiscriminately.“ A shortage of prey, he suggests, could provide the spark.

But Tom Sherratt, an evolutionary biologist at Carleton University in Ottawa, is not so sure that scarlet kingsnakes’ mimicry will become sketchier over time. “Many of the predators — especially avian ones — are mobile and may visit locations where the model is present, which might explain why selection for mimicry still lingers.”

Citations

Akcali, C. & Pfennig, D. W. Biol. Lett. http:/dx.doi.org/10.2098/rsbl.2014.0304 (2014).

Harper, G. R. Jr & Pfennig, D. W. Proc. R. Soc. B 274, 1955–1961 (2007).

Thursday, June 12, 2014

Convergent snakes

The southern shovel-nosed snake is a small, desert-dwelling 
species of Australian elapid snake that feeds almost exclusively on 
lizard eggs. Photo Credit: Daniel Rabosky.
On opposite sides of the globe over millions of years, the snakes of North America and Australia independently evolved similar body types that helped them move and capture prey more efficiently.

Snakes on both continents include stout-bodied, highly camouflaged ambush predators, such as rattlesnakes in North America and death adders in Australia. There are slender, fast-moving foragers on both continents, as well as small burrowing snakes.

This independent evolution of similar body forms in response to analogous ecological conditions is a striking example of a phenomenon called convergence. Yet despite similarities in outward appearance, a new University of Michigan study shows that look-alike snakes from the two continents differ dramatically in at least one major attribute: diet.

"Most biologists tend to assume that convergence in body form for a group of organisms implies that they must be ecologically similar," said U-M evolutionary biologist Daniel Rabosky. "But our study shows that there is almost no overlap in diet between many of the snakes that are morphologically very similar."

Rabosky is an assistant professor in the Department of Ecology and Evolutionary Biology and curator of herpetology at the U-M Museum of Zoology. He is co-author of a paper on the topic to be published online June 10 in the journal Proceedings of the Royal Society B. The first author is U-M doctoral student Michael Grundler.

While North America is home to at least seven distinct groups of "advanced" snakes, only one major group -- the elapids -- colonized Australia roughly 12 million years ago. Elapids, which have hollow, fixed fangs through which they inject venom, are found worldwide and include king cobras, coral snakes, mambas and kraits.

Over millions of years, evolution allowed Australia's elapids to diversify and specialize through a process called adaptive radiation. They settled into varied habitats and split into roughly 100 species that include snakes with some of the most toxic venom known: taipans, brown snakes, death adders and tiger snakes.

Over time, the Australian snakes took on most of the body forms found in North American snakes.

Grundler and Rabosky compared those body forms by analyzing preserved specimens in the collections of the University of Michigan Museum of Zoology, the Field Museum of Natural History and the Western Australian Museum. They made measurements of head and body dimensions from 786 specimens representing 248 species.

"We found that the morphologies of Australia elapid snakes have evolved into the same types of body forms seen across a much more diverse set of snakes from North America," Grundler said. "For example, Australia has the death adder, a stout-bodied ambush predator that looks, for all practical purposes, like a typical viper.


"Vipers are a family of fanged, venomous snakes that includes pit vipers such as rattlesnakes, copperheads and bushmasters. But the death adder is not a viper and is in fact much more closely related to other Australian elapid snakes, most of which look nothing like vipers."


Grundler and Rabosky surveyed the published literature for data on the feeding habits of snakes on both continents. The feeding habits were placed in eight prey categories: invertebrates such as insects, earthworms, mollusks and crustaceans; fish; amphibians; lizards and snakes; lizard and snake eggs; birds; bird eggs; and mammals.

In many cases, Australian and North American snakes that are similar in appearance differ greatly in their diets, the U-M researchers found.

For example, most small snakes that live in sand or leaf litter in North America eat invertebrates such as spiders, scorpions, slugs and centipedes. But in Australia, those snakes tend to be specialists on lizards and other snakes.

The physical similarities between North American and Australian snakes are thought to reflect evolutionary advantages that those body forms provide for locomotion, foraging, or habitat use, according to the authors.

Citation
M. C. Grundler and D.L. Rabosky. 2014. Trophic divergence despite morphological convergence in a continental radiation of snakes. Proceedings of the Royal Society B, 281 1787 20140413; doi:10.1098/rspb.2014.0413




Sunday, June 1, 2014

10 new speices of helmeted turtles



The  “true“ Pelomedusa subrufa remains relatively small, and it is a 
eritable survivor: In Namibia, it can endure drought periods of 
up to 6 years by burying itself underground. A. Schleicher
Scentists at the Senckenberg Research Institute revealed that the African helmeted terrapin Pelomedusa subrufa actually comprises at least 10 different species. Until now, it had been considered to represent a single species, with a distribution spanning most of Africa, Madagascar and Arabia. The new classification also results in a revised assessment of its conservation status: at least one of the newly described species is seriously endangered. The underlying studies were published in the scientific journal Zootaxa.

The African helmeted terrapin Pelomedusa subrufa prefers small water bodies, but it is also able to survive drought periods of several years -- by burrowing underground. Reaching a maximum shell length of 30 cm, these turtles are widely distributed. They are found from South Africa north to the Sahel Zone, in Madagascar and on the Arabian Peninsula. This wide distribution range and their ability to survive long periods of drought led to its classification as "not endangered."

"However, our research shows that previous assumptions were basically incorrect," says Professor Uwe Fritz, director at Senckenberg in Dresden. In cooperation with an international team of scientists, among them researchers from South Africa and Namibia, he examined the turtles using morphological methods and the molecular genetic approaches. "Our results indicate that not one, but at least ten species are involved in this complex -- and perhaps even more," explains Fritz.

Altogether, the scientists from Dresden examined approximately 350 turtles, 200 of which underwent genetic testing. Among others, they also genetically analyzed samples from museum specimens -- some more than 100 years old.

"Up to now, the African helmeted terrapin was considered a widely distributed species and, therefore, not endangered, since it was assumed that the same species occurred throughout Africa. Our research shows that many distinct species are involved and that the distribution of each species is much more limited," says Fritz. "Due to this, some of the species are probably much more endangered than previously assumed." One of the newly described turtles may actually be threatened by extinction, due to severe water shortage in its home on the southwestern Arabian Peninsula.

However, there is also good news at least for some countries: South Africa has gained an additional turtle species. Thanks to the recent split, two species of helmeted terrapins are now found in the country, one is distributed over most of South Africa, while the second species is confined to South Africa's Limpopo province. This even topped by Tanzania, where three distinct species occur!
Citations
Uwe Fritz, Alice Petzold, Christian Kehlmaier, Carolin Kindler, Patrick Cambell, Margaretha D. Hofmeyr & William R. Branch. Disentangling the Pelomedusa complex using type specimens and historical DNA (Testudines: Pelomedusidae). Zootaxa, 3795 (5): 501%u2013522

Alice Petzold, Mario Vargas-Ramirez, Christian Kehlmaier, Melita Vamberger, William R. Branch, Louis du Preez, Margaretha D. Hofmeyr, Leon Meyer, Alfred Schleicher, Pavel ┼áiroky & Uwe Fritz Zootaxa. A revision of African helmeted terrapins (Testudines: Pelomedusidae: Pelomedusa), with descriptions of six new species. Zootaxa, May 2014