Archive for May, 2011

The Plot “Thickens”

Tuesday, May 17th, 2011

If you have ever had the misfortune of turning over a log or rock in eastern Oklahoma and grabbing a black salamander with white spots, you know that washing off the thick, sticky liquid that they secrete from their skin in defense is no easy matter. Imagine being a small predator like a snake, biting the salamander, getting a mouthful of that sticky stuff, and then trying to rub it off in the leaf litter ending up with a mouthful of leaves stuck to your mouth! These salamanders, which look pretty much the same from mountain ridge to mountain ridge, and even resemble a lowland salamander, form a complex of species whose identities and relationships are just beginning to be understood. To the layman, these are known as the “slimy” salamanders.

The salamander Plethodon ouachitae, occurs along several ridges in the Ouachita Mountains and is commonly known as the Rich Mountain Salamander.

The Rich Mountain Salamander (P. ouachitae) occurs along several ridges in the Ouachita Mountains.

Dr. Don Shepard, a former graduate student from the University of Oklahoma, has combined field studies with DNA sequence data to unravel relationships among these species. Until recently, these salamanders have been considered as four species. One, Plethodon albagula, appears to be widespread in lowlands and the Ozark foothills of eastern Oklahoma, extending up into Missouri. Three other species, P. caddoensis, P. fourchensis, and P. ouachitae, each occur on their own mountain ridges in the Ouachita Mountains of southeastern Oklahoma and southwestern Arkansas. If only it were that simple!

By combining DNA sequence data with known rates of evolutionary change for specific genes, Don has discovered that not only have some of these “species” experienced divergence into genetically different populations, the causes of divergence differ among species. For P. ouachitae and P. fourchensis, genetically different populations are associated with mountain ridges, indicating that populations were isolated on mountain tops as the climate slowly changed over geologic time. Why would they become isolated? The answer is that these salamanders require a specific set of environmental conditions to survive. These include relatively cool temperatures and high humidity, usually associated with mountain tops. The salamanders appear unable to adapt to warmer and drier conditions so they simply live in the same kind of microhabitats that they lived in historically. This inability to adapt is referred to by scientists as “niche conservatism.”

For P. caddoensis, diversification is associated with stream drainages. Four distinct lineages within P. caddoensis have been identified from each of the following four streams; lower Caddo River, Upper Caddo River, Brushy Creek, and Cossatot and Little Missouri Rivers. Diversification in this “species” appears tied to more recent climatic change and specialized niche characteristics of the salamanders, primarily related to thermal and humidity variables associated with stream drainages.

The Western Slimy Salamander, Plethodon albagula, occurs from Missouri south to extreme southeastern Oklahoma and into Texas.

The Western Slimy Salamander (P. albagula) occurs from Missouri south to extreme southeastern Oklahoma and into Texas.

Dr. Shepard is now beginning to examine the lowland and widespread “species” P. albagula. No doubt this species has undergone some interesting divergences in the past, but what the pattern is and how it occurred remains a mystery to be unraveled. So, the next time you pick up one of these so-called “slimy salamanders,” reflect on their evolutionary history and what they tell us about past events underscoring the remarkable diversity that we see today in eastern Oklahoma. Oh, and if you have been slimed, try WD-40 followed by soap and water. WD-40 seems to be a universal solvent and will clean many things!

Dodging Turtles

Tuesday, May 17th, 2011

With the days getting warmer, box turtles begin moving around, often finding themselves on paved highways as they search for mates and good areas to feed. Not to be confused with rocks, box turtles will squish when run over. Similar to most other reptiles (and, interestingly Opossums and Armadillos), box turtles are oblivious to traffic. This might seem surprising, considering that turtles in general have excellent sight. For example, if you try to sneak up to a bunch of sliders basking on a log in a pond, you will be lucky to get within 100 yards of the turtles before they “slide” into the water. Of course, box turtles cannot slide into the water because they spend most of their time on land. Nevertheless, they see you from a long distance when approaching. When a box turtle detects something moving within the range of its eyes, it remains perfectly still, with its head up in a periscope-like fashion as shown in the first photo below. Box turtles are difficult to detect in their natural habitats if they do not move. If you are lucky enough to see one, by the time you get your camera set to photograph it, the turtle will likely pull its head and legs into the shell and close it.

Ornate Box Turtle with head up, remaining motionless in an attempt to be overlooked.

Ornate Box Turtle with head up, remaining motionless in an attempt to be overlooked.

Oklahoma has two species of box turtles, the Ornate Box Turtle, which is most common in western Oklahoma, and the Three-toed or Eastern Box Turtle, which is common in central and eastern Oklahoma. Both species occur in central Oklahoma, but the Ornate Box Turtle is less common. Like most animals, box turtles usually know where they are going when they head out across a highway. Given that an adult box turtle might be 40 years old or older, the highway may not have even been there when it hatched from an egg. Even if the highway is older than the individual turtle, neither highways nor cars are in the evolutionary history of box turtles. From the perspective of a box turtle, a highway is just a strange piece of ground that they have to cross to get where they are going.

Three-Toed Box Turtle caught in the act of feeding on some vegetation along the edge of a small pond. Three-toed Box Turtles are highly variable in coloration.

Three-Toed Box Turtle caught in the act of feeding on some vegetation along the edge of a small pond. Three-toed Box Turtles are highly variable in coloration.

How can you help? The best thing that you can do to help box turtles, is to watch for them on roads when either driving or sitting in a car. When you see one, the first thing to do is avoid running over it. If there is no traffic, you can stop and help it across the road. If you do stop and move a turtle (of any kind) be sure to set it well off the road and on the side it was heading for. However, keep in mind that roads and highways are dangerous for people as well, and you should not stop if doing so puts you in harm’s way. Simply paying attention and doing your best to avoid running over turtles goes a long way in helping them out. In addition, tell everyone that you know to start watching for and avoiding turtles on the highway.

Three-toed Box Turtle upside down with the shell completely closed. The lower shell (plastron) has two hinges which allow the turtle to close itself in the shell. Most turtle species cannot completely close the shell. Box turtles close the shell immediately when first disturbed and often remain this way for an hour or more. When they do come back out, they first partially open the front of the shell and peek out to see if they are safe.

Three-toed Box Turtle upside down with the shell completely closed. The lower shell (plastron) has two hinges which allow the turtle to close itself in the shell. Most turtle species cannot completely close the shell. Box turtles close the shell immediately when first disturbed and often remain this way for an hour or more. When they do come back out, they first partially open the front of the shell and peek out to see if they are safe.

Why should we care about turtles? First and foremost, turtles are part of the natural biodiversity of the planet, and as such, they play important ecological roles as grazers on fruits and predators on certain insects and other invertebrates. Second, they were here first. The first turtle fossils appeared in the mid Triassic, about 225 million years ago. Box Turtles are in the family Emydidae, which also includes Sliders, Painted Turtles, and Map Turtles, to mention a few. The family Emydidae dates back to at least the late Cretaceous, some 75–80 million years ago. The family that we belong to, the Hominidae, dates back only about 15 million years, and modern man (Homo sapiens) as we know it, dates back less than 200,000 years. Box turtles certainly have been in Oklahoma long before the influx of Europeans and even long before Native Americans settled the land. So, as Woody Guthrie sang in 1940, “This land is your land, this land is my land…”—we share the land with box turtles and all other native animal and plant life, and we should do our best to maintain that relationship.