Showing posts with label lizards. Show all posts
Showing posts with label lizards. Show all posts

Tuesday, July 26, 2011

Turtles + Lizards Form A Clade?

Famous for their sluggishness, turtles have been slow to give up the secrets of their evolution and place on the evolutionary tree. For decades, paleontologists and molecular biologists have disagreed about whether turtles are more closely related to birds and crocodiles or to lizards. Now, two scientists from the Mount Desert Island Biological Laboratory in Bar Harbor, Maine, and their colleagues from Dartmouth College and Harvard and Yale Universities have developed a new technique using microRNAs for classifying animals, and the secret is out. Turtles are closer kin to lizards than crocodiles.

To reach their conclusion, published in Nature News and Biology Letters, the research team looked at a newly discovered class of molecules called microRNA. Most of the genetic material or DNA that scientists study provides the code for building proteins, large molecules that form an essential part of every organism. But microRNAs are much smaller molecules that can switch genes on and off and regulate protein production. They are also remarkably similar within related animal groups and provide important clues for identification.

“Different microRNAs develop fairly rapidly in different animal species over time, but once developed, they then remain virtually unchanged,” said Kevin Peterson, a paleobiologist at MDIBL and Dartmouth College. “They provide a kind of molecular map that allows us to trace a species’ evolution.”

Peterson worked with Ben King, a bioinformatician at MDIBL. “My role in the study was to enhance our software so we could find new and unique microRNAs in the lizard genome,” King said. “We identified 77 new microRNA families, and four of these turned out to also be expressed in the painted turtle. So we had the evidence we needed to say that turtles are a sister group to lizards and not crocodiles.”

Though few creatures have been as puzzling as the turtle, the research team plans to use its microRNA analysis on other animals to help determine their origins and relationships as well. It is also developing a web-based platform to share the software with other researchers around the world.

In addition to King and Peterson, the research team included Tyler Lyson and Jacques Gauthier from Yale University, Eric Sperling from Harvard University, and Alysha Heimberg from Dartmouth College.

Tyler R. Lyson, Erik A. Sperling, Alysha M. Heimberg, Jacques A. Gauthier, Benjamin L. King and Kevin J. Peterson. 2011. MicroRNAs support a turtle + lizard clade. Biology Letters doi: 10.1098/rsbl.2011.0477.

Monday, June 20, 2011

Aripo Savanna & its Herpetofauna

Trinidad’s Aripo Savanna complex of tropical grasslands, palm islands, marsh forest and moriche palms with numerous slow moving streams, ponds, and puddles. On June 18-19 the Herp Group from the Trinidad and Tobago field Naturalists Club surveyed the herpetofauna. The weather cooperated to a degree with occasional showers and thunderstorms and blistering heat, which creates a very nice sauna-like effect. The TTFNC-HC will summarize the results elsewhere, but here are a few of the highlights.
Rare creatures are sometimes sited on the savanna. Here is Graham White looking 
for them while well camoflaged.

Aripo Savnna 1. The largest remaining remanant of the savanna.

Stevland Charles and Edmund Charles inspect Marsh Forest Vegetation
A Marsh Forest Pond
An Aripo Savanna Sundew.
Leptodactylus fuscus, the most commonly seen and heard amphibian on the Savanna,
The Scorpion Mud Turtle, Kinosternon scorpioides, a savanna and marsh
 forest inhabitat.
The Trinidad Wood Turtle, or Galup, Rhinoclemmys punctularia, another Marsh
Forest - Savanna chelonian.

Predator & prey. The Horse Whip Snake, Oxybelis aeneus and 
 its prey, the Streaked Lizard, Gonatodes vittatus.
A male Hypsiboans punctata (Hylidae) that was calling from this leaf.
The poorly known microhylid frog, Elachistocleis surinamensis
 is quite common  in the Marsh Forest and at the forest edge.

One of the day groups, with Mike Rutherford examining a turtle (middle).

Wednesday, June 15, 2011

Looking For Squamates in the Bocas

Between working in the UWITT Museum and running around Trinidad to find supplies we do occasionally get into the field for some serious collecting and fun. On Tuesday, Stevland Charles, Mike Rutherford, and Josh Traub, and I visited two of the Bocas Islands – Gaspar Grande and Monos  - the major goal was to find more coral snakes from each of the islands. However, snakes are notoriously difficult to find no matter how much ground cover you turn. Keeping that in mind we hoped to at least add some footnotes to the islands’ herpetology, and collect some specimens that could supply tissue for molecular studies. Mike was also interested in adding land snails to the UWITT collection. The Bocas Islands (Bocas del Dragon) lie between Trinidad and Venezuela, in the  “Dragons' Mouth”.
Our first stop was Gaspar Grande, a small island composed mostly of limestone. After exiting the boat and a short hike we were at the opening of a sinkhole that descended into a cave; local people had used this as a dump. Using a rope all of us were soon exploring the sink and collecting land snails for Mike and Gonatodes for Stevland. 
Mike and Josh looking for snails in the sinkhole on Gaspar Grande.
Leaf-nosed bats would occasionally brush us. Out of the hole and walking up the trail Gymnopthalmus and Ameiva were quickly getting out of our way. At the top of the  hill were  several relicts of World War II, anti-aircraft gun emplacements, now covered with graffiti and inhabited by some of the island’s lizards. Despite several hours of looking we collected only Gymnopthalmus, a Gonatodes vittatus, and some snails.
We met the boatman at noon and headed for Monos, just a few minutes away.
Stevland directing the boatman to the landing site.
 Landing on Monos, was a bit tricky, the boatman let us off on a crumbling concrete wall several hundred feet from shore. The required us to scramble over slippery, broken concrete to reach shore. As we approached the beach the volume of plastic litter and other man-made junk was alarming. Stevland had been to this location before, and we walked through the coastal palms in to a more seasonal dry forest to a house. As if he knew where to look - an outhouse- Stevland produced a Hemidactylus palichthus within a minute of arrival. This gecko's presence in the Western Hemisphere is a biogeographical puzzle, all of its close living relatives are in Africa, and it is the only Western Hemisphere Hemidactylus that is endemic. All other Western Hemisphere Hemidactylus are  introduced.  
The gecko, Hemidactylus palichthius.

We walked along a stream bed only to encounter a large bamboo die-off that made following the gully exceptionally difficult. As we got deeper into the forest Plica plica became more obvious and abundant, these arboreal and scansorial tropidurid lizards are quite social and on some of the larger tree trunks 3 or 4 individuals were obvious. 

Josh  with a Plica plica on the tree buttress.

Monos has a large amount of human made garbage washing up on its beaches.

Snakes eluded us until we got out of the gully onto the hillside, within a few minutes a Mastigodryas was spotted, but despite being in contact with the hands of two of us it escaped. As we headed back to the beach Mike spotted a Boa constrictor laid out along a broken palm frond. It was a male, about 1.3 m long and had two blood swollen ticks attached to its head. 

Boa constrictor with ticks.

Boa constrictor after tick removal.
After removing the ticks, and a photo session, we were out of water and it was time to met the boatman for the return trip to Trinidad. Despite the fact that we did not find any Bocas coral snakes, the day was not a total loss.

Thursday, December 9, 2010

Reptile Extinction in the Agean

This is an almost unedited press release from

A sample group of Aegean wall lizards 
was captured during field work on one 
of the Greek study islands. 
Credit: Johannes Foufopoulos
A wave of reptile extinctions on the Greek islands over the past 15,000 years may offer a preview of the way plants and animals will respond as the world rapidly warms due to human-caused climate change, according to a University of Michigan ecologist and his colleagues.
The Greek island extinctions also highlight the critical importance of preserving habitat corridors that will enable plants and animals to migrate in response to climate change, thereby maximizing their chances of survival.

As the climate warmed at the tail end of the last ice age, sea levels rose and formed scores of Aegean islands that had formerly been part of the Greek mainland. At the same time, cool and moist forested areas dwindled as aridity spread through the region.

In response to the combined effects of a shifting climate, vegetation changes and ever-decreasing island size, many reptile populations perished.

To gain a clearer understanding of the past consequences of climate change, Johannes Foufopoulos and his colleagues calculated the population extinction rates of 35 reptile species---assorted lizards, snakes and turtles---from 87 Greek islands in the northeast Mediterranean Sea. The calculated extinction rates were based on the modern-day presence or absence of each species on islands that were connected to the mainland during the last ice age.

Foufopoulos and his colleagues found a striking pattern to the island extinctions. In most cases, reptile populations disappeared on the smallest islands first---the places where the habitat choices were most limited.
Especially hard hit were "habitat specialist" reptiles that required a narrow range of environmental conditions to survive. In addition, northern-dwelling species that required cool, moist conditions showed some of the highest extinction rates. 

The study results appear in the January edition of American Naturalist.

The researchers conclude that a similar pattern of extinctions will emerge at various spots across the globe as the climate warms in the coming decades and centuries. In addition to adapting to a changing climate, plants and animals will be forced to traverse an increasingly fragmented natural landscape. 

Foufopoulos, J., A. Marm Kilpatrick, and A. R. Ives. 2011. Climate Change and Elevated Extinction Rates of Reptiles from Mediterranean Islands. The American Naturalist 177:19-129.

Friday, December 3, 2010

Cruising For Food

A cruising forager. JCM
Foraging behavior in lizards has been classically described as either active foraging or ambush (also called sit-and-wait). Both types of foraging behavior have been correlated with morphological, behavioral, and habitat traits. Active foragers, for example, have higher activity levels, caloric intake, and body temperatures compared with ambush foragers.  However, chameleons have unusual morphological and behavioral traits that undoubtedly influence feeding behavior. The moniker, “cruise forager,” was first suggested by Regal (1978) as an intermediate stage between active and ambush foraging. Regal (1983), later defined cruise foraging  as an animal that moves, stops, scans the environment, then moves, stops, and scans again. Observing the chameleon Bradypodion pumilum foraging for food prompted Butler (2005), to propose chameleons compose a third foraging class, the “cruise foragers.”  Hagey et al. (2010) observed Jackson’s chameleon, Chameleo jacksonii xantholophus on the island of Hawai’i. The species is endemic to Mt. Kenya, Kenya, but was introduced to Hawai’i in the early 1970’s and has spread to several other islands in the Sandwich group. The lizards were filmed, measured, and their microhabitat described. The video was used to quantify the lizards’ foraging behavior and it was compared to the behavior reported by Butler (2005). The results suggested that Jackson’s Chameleon exhibits a moderate percent time moving (19.7%), has a low number of moves per minute (the mean was 0.24); and a very slow locomotion speed. This combination is rarely seen in other lizard species, but it is strikingly similar to data from the only other chameleon studied, B. pumilum. The authors suggest that another lizard, other than other true chameleons (family Chamaeleonidae), that may be a cruise forager is the polychrotid, Chamaeleolis, which is in a different lineage than the true chameleons – it is closely related to the anoles. As for “cruise foraging” as a new class of hunting behavior in lizards, these authors agree that it should be recognized.

Butler, M. A. 2005. Foraging mode of the chameleon, Bradupodion pumilum: A challenge to the sit-and wait versus active forager paradigm? Biological Journal of Linnean Society, 84:797–808.

Hagey, T. J., J. B. Losos, and L. J. Harmon. 2010.  Cruise Foraging of Invasive Chameleon (Chamaeleo jacksonii xantholophus) In Hawai'i. Breviora 519:1-7.

Regal, P. J. 1978. Behavioral differences between reptiles and mammals: An analysis of activity and mental capabilities, pp. 183–202, In N. Greenberg, and P. D. MacLean (eds.), Behavior and Neurology of Lizards. Rockville, Maryland, National Institute of Mental Health.

Regal, P. J. 1983. The adaptive zone and behavior of lizards, pp. 105–118. In R. B. Huey, E. R. Pianka, and T. W. Schoener (eds.), Lizard Ecology: Studies of a Model Organism. Cambridge, Massachusetts, Harvard University Press.