Thursday, February 14, 2013

A Tale of Three Turtles

Although snakes and salamanders tend to get a lot of attention on this blog, turtles have certainly had their more recent share of the spotlight. I wanted to touch on a small group of turtles which were once members of a single genus, but have within the past decade or two been cleaved into a two genera; one being monotypic and the other containing two species. Spotted, wood, and bog turtles were all classified in the genus Clemmys prior to 2001. It's easy to see why, as all three species share morphological characteristics which are similar, and all three are considered to be semi-aquatic.

Wood Turtle, Glyptemys insculpta, adult male, Michigan

Bog Turtle, Glyptemys muhlenbergii, adult female, New Jersey

Spotted Turtle, Clemmys guttata, adult female, Michigan

However, the emergence of modern molecular genetics and its role in constructing more accurate phylogenies didn't emerge until the late 1990s and most species had been classified before that time mostly on morphological characteristics. Feldman & Parham, 2002 used both cytochrome B and the ND4 gene to help examine the classification and evolutionary history of the Emydine turtles and found that wood and bog turtles were much more closely related to one another; both species have karyotype which contains fifty chromosomes,  than they are to the spotted turtle. This coupled with other morphological characteristics helped lead to reclassification of wood & bog turtles to a new genus, Glyptemys. The etymology of the genus name comes from the Greek words glypt, meaning "carved," and emys, meaning turtle. This literally translates to "carved turtle" and is an accurate description for the highly ornate carapaces of both the bog & wood turtle, something not exhibited in the spotted turtle.

Bog Turtle

Glyptemys muhlenbergii

A denizen of calcareous wetlands in scattered locations across the eastern United States, the bog turtle is a small, secretive species which spends much of its time hidden meandering through these sensitive habitats. It was named in honor of Gotthilf Heinrich Ernst Muhlenberg, an 18th century botanist from Pennsylvania who first discovered this species in his millpond. The bog turtle is the smallest turtle species which is known to inhabit North America, most adults attain lengths of four inches. The head and neck are usually black or mahogany in coloration and two bright orange or yellow blotches which are found on either side of the neck. Like its close cousin the wood turtle, the carapace is highly sculptured and features prominent growth rings on each scute. It is usually dark in coloration, but may feature radiating lines or markings which can be mahogany in color.

Bog turtles prefer calcareous wetlands such as fens, bogs, wet meadows, and sphagnum seepages. These wetlands are often fed by spring seepages which supply cold, slowly moving water to these habitats which is a necessity for the overwintering areas for bog turtles. They also function as a cool retreat during the hottest parts of the year. The northern population of Bog Turtles in the United States is generally considered to be a lowland species, but there are exceptions. While the southern population is generally found in high elevation mountain bogs in the southern Appalachians of Georgia, Tennessee, and the Carolinas.

Bog turtles have suffered significant declines across its range due to loss of critical habitat, vegetative succession, and illegal collection. It has been listed as a Threatened species under the Endangered Species Act since 1997 and receives protection under federal law by the U.S. Fish & Wildlife Service. It is also listed as a Threatened or Endangered species in every state it inhabits. State, federal, and private agencies continue to protect and manage habitat for the bog turtle and considering many populations occur on private land, the future for the species is certainly optimistic.

Wood Turtle 

Glyptemys insculpta

The name Glyptemys insculpta literally translates into "sculptured turtle" and there's no better way to describe the carapace of the wood turtle. Each scute has ornate, concentric growth rings that have been likened to the inside of a tree, another place where this species gets it's common name. The carapace coloration is usually brown in color and Michigan specimens usually feature many radiating yellow lines. The plastron is yellow in color with black outer blotches. The head is partially black in coloration, while the neck and limbs are yellow or yellowish orange in color with some black coloration as well. Adults are large, attaining carapace lengths between 6.5-9.5". Males are usually slightly larger then females and feature a concave plastron, an enlarged and widened head, and a long thick tail.

In Michigan, wood turtles inhabit medium sized rivers with sandy or gravel substrates with ample surrounding forest. They occasionally wander into smaller streams and tributaries of larger streams. This species is semi-aquatic and spends much of it's time form September through May in and around the rivers themselves, but often move upland into adjacent habitats in the summer months. These terrestrial habitats include woodlands, meadows, pastures, and wetlands where they spend much of their time foraging on earthworms, slugs, mushrooms, and berries. Females tend to wander greater distances from the river corridor than males, which can be quite territorial and appear to spend much of their time patrolling their river corridor for mates and potential intruding males. 

Wood turtles are found throughout the upper peninsula and in the northern half of the lower peninsula where suitable river corridor habitat is available. A Species of Special Concern here in Michigan, wood turtles have suffered significant declines across its range due to illegal collection, habitat loss, nest predation, and road mortality. Their striking appearance, charismatic personality, and rarity make them highly sought after in the herp community. Like other rare and declining turtle species, nest predation and low recruitment of juveniles continues to be the single greatest threat to future of the wood turtle.

Spotted Turtle

Clemmys guttata

Spotted turtles are easily recognizable by their dark black carapace and scattered yellow spots. The plastron is yellow or orange with alternating black markings, but it may occasionally be mostly black altogether. The limps are reddish orange on the underside and black with yellow spots on top. Adults are small, with carapace lengths ranging from 3-5". This species is also sexually dimorphic, males have a concave plastron and usually have a dark head and chin while females have a flat plastron and an orange striped chin. It's noticeable that this species does not exhibit the sculpted carapace of the two Glyptemys species, and also does not feature the same pronounced beak seen in these two species.

Spotted turtles are almost always associated with wetlands with shallow, clean water and a muddy or silty bottom and ample emergent vegetation. These habitats include boggy ponds, prairie fens, grassy marshes, and sphagnum seepages. In the early spring they can be seen basking on sedges on warm, sunny afternoons like the individual pictured above. Spotted turtles are incredibly cold tolerant and are among the first species of turtle to begin basking in the early spring. As temperatures rise, spotted turtles eventually dig into the mud to estivate during the hottest and driest parts of the summer. Spotted turtles have been known to inhabit vernal pools in the northeast, but may also inhabit them during the spring months in Michigan as shown in the picture below.

Unfortunately the story of this species in Michigan and across it's range is saddening. Spotted turtles have experienced severe declines due to habitat loss by the draining of wetlands for agriculture, road mortality, nest predation, and illegal collection. These declines have been so severe that the species is listed as Threatened in Michigan. Spotted turtles are rare and are found in scattered locations in the southern and western parts of the lower peninsula.

The Verdict

 Constructed Phylogeny using ND4 Gene - Stephens et al., 2003

Based on phylogenetic analyses and morphology, it's easy to see why both Glyptemys insculpta and Glyptemys muhlenbergii were cleaved from the Clemmys genus and reclassified as their own, separate genus. Though all of these species share a fairly recent common ancestor, spotted turtles are also rooted from this part of the Emydidae family. Genetic analysis seems to show that at some point in the evolutionary history of this group, there was a divergence between Clemmys guttata and the common ancestor of the monophyletic group shown above. The Western Pond Turtle; formerly Clemmys marmorata, was also reclassified into a new genus Actinemys, and seems to have undergone a divergence with a common ancestor of the Blanding's Turtle (Emydoidea blandingii) and the European Pond Turtle (Emys orbicularis). Overall, it's a pretty interesting story involving this group of turtles.

Wednesday, February 6, 2013

Michigan Senate Bill Seeks to Restrict DNR's Ability to Manage Lands for Biodiversity

It's not terribly often that legislation as ignorant as this one comes along. Michigan Senate Bill 78 was proposed by Senator Tom Casperson (R) from Escanaba, it seeks to limit the Michigan DNR's ability to manage lands with the purpose of preserving biodiversity. The bill is scheduled to be presented this Thursday morning, February 7th, in front of the state senate, but it could be rescheduled due to pressure from concerned citizens and environmental groups. Here's the raw details of the bill itself:

Senate Bill 78 (as introduced 1-24-13)
r: Senator Tom Casperson
Committee: Natural Resources, Environment and Great Lakes
Date Completed: 2-1-13


The bill would amend several parts of the Natural Resources and Environmental
Protection Act to do the following:

  • Prohibit the Department of Natural Resources (DNR) and the Natural Resources Commission from promulgating or enforcing a rule or an order that designates or classifies an area of land specifically for the purpose of achieving or maintaining biological diversity. 
  • Delete the conservation of biological diversity from the DNR's duties regarding forest management, and require the Department to balance its management activities with economic values. 
  • Eliminate a requirement that the DNR manage forests in a manner that promotes restoration.
  • Provide that a State department or agency would not have to designate or classify an area of land specifically for the purpose of achieving or maintaining biological diversity.
  • Eliminate the restoration of natural biological diversity from the definition of "conservation."
  • Eliminate a reference to "unusual flora and fauna" in the definition of "natural area."
  • Delete a legislative finding that most losses of biological diversity are the result of human activity.
There are so many holes in the logic of this bill that I don't even know where to begin. As the human population continues to multiply and expand outward, natural areas and habitat for wildlife species are becoming increasingly small and hard to come by. The Michigan DNR's mission statement reads: "The Michigan Department of Natural Resources is committed to the conservation, protection, management, use and enjoyment of the State's natural resources for current and future generations." 

Promoting biodiversity, threatened & endangered species, climate change, restoration, and invasive species are all facets of the work that the DNR does in the state. For a long time, a scientifically sound based approach to land management has led to the rebound and stabilization of Michigan's ecosystems and wildlife. Taking a step backward in the way the DNR makes management decisions and removing scientific knowledge from the table is the last thing the state needs moving forward into a future where many environmental concerns & questions remain. Please, take the time to write an email or make a call to any of these state representatives to make your voice heard.

DNR Director Keith Creagh:
Call: 517-373-2329

Tom Casperson: Call: 517-373-7840

Patrick Colbeck: Call: 517-373-7350 
Arlan Meekhof: Call: 517-373-6920 
David Robertson: Call: 517-373-1636, 
Michael Green: Call: 517-373-1777
Darwin Booher: Call: 517-373-1725
Howard Walker: Call: 517-373-2413 

Sunday, February 3, 2013

The Importance of Evolution

The Phylogenetic Tree of Life

If there's one debate that causes more controversy than anything else in traditional America, it's evolution versus creation. Before Charles Darwin presented his hypothesis of evolution by natural selection when he published On the Origin of Species in 1859, the scientific community's view of the world and the origin of all biodiversity was that which has been presented in bible. But discoveries including the fossil record and advances in other scientific disciplines like geology led some skeptics like Darwin to question the simple explanation to the unknown origin of life and earth to some sort of creation. Even today more than 150 years after Darwin's theory was presented and mounds of evidence supporting it have been found, about 46% of the United States still believes that the most likely explanation to our origins is the Genesis story and that evolution is a fallacy. That's a pretty staggering percentage, considering how far scientific knowledge & research has gotten us in terms of technology, medicine, and biology. It also beckons us to question why so many people don't "believe" in Darwinian evolution. I'll get into the term "believe" in terms of evolution a little later and why it false to use that wording a little bit later. But first, let's dig into evolution a little bit.

The complexity and diversity we see in herpetofauna is only a fraction of how biodiverse our world is as a whole. When Darwin first visited the Galapagos islands, he was blown away at the tremendous diversity of species he saw from island to island, and how specialized each species was to its particular ecological niche. A group of finches caught his eye in particular. Noticing a wide variety of beak sizes and shapes, Darwin wondered what the chances were that such this highly adapted group of finch species on a single island came about by a single creation event. By studying the birds Darwin found that each species has exploited a particular ecological niche, it was the only way that such a vast diversity of finches could coexist without driving each other into extinction via competitive exclusion. He postulated that each species had evolved a particular beak morphology to suite a particular diet.

Later studies of the larger beaked species found that the beak size and depth varied throughout years of drought and higher precipitation. In years of severe drought, the beaks of the offspring showed a higher amount of larger beaks to help crack tougher, drier nuts. While in years of appropriate precipitation, offspring showed a higher amount of more moderately sized beaks. This idea and others that Darwin published in his book shook the foundations of scientific community and laid the framework to what we now know about evolution. So what is evolution, how do we define it? It can simply be explained as gradual change of organisms through time or descent with modification through natural selection. A vast amount of ecological pressures require species to adapt, survival of the fittest. Natural selection is the gradual, non-random process by which characteristics become either more or less common in a population as a function of differential reproduction of their bearers This ensures that those individuals with favorable traits are the ones whose genes get passed on to the next generation. Natural selection works at the individual level, but it's consequences affect species at the population level. This has lead to vast changes in species over time. The development of the geologic time scale and the idea of deep time has helped make the process of evolution more clear, it has taken millions of years for the extant species we see today to evolve to where they are now. Other advances, particularly in genetics, have helped scientists gain further insight into how species evolve both genetically and morphologically. Phylogenetic analyses using such concepts have helped reconstruct phylogenies and more accurately classify organisms within families in regards to their evolutionary history. Evolution is the fundamental concept in biology, and it relates to all other disciplines in science.

The best part about the scientific method is that is never seeks to prove a theory, but rather to disprove it. Mounds of evidence in support for evolution have been found in the past few hundred years and the theory has been tested again, and again, and again. It has been widely accepted by the scientific community and is close to a biological fact as we can get. Yet, almost half the population of United States considers it to be hogwash and favors creationism over evolution. How can this be? The problem is where religion interferes with education, particularly in public and private schools. I was raised in a Christian home and attended a private Lutheran school from K-8th grade. Throughout my time time there, I was taught over and over again how evolution wasn't true, that the earth was only a few thousand years old, and the teaching of evolution was an attempt to remove God from the picture. Though I won't bring my own religious beliefs into this, I will say that the things I was taught was a direct attempt to curb my thinking to the way someone else deemed to be correct. It not only curbed my curiosity about the natural world, but also limited my ability to think critically. It wasn't until I reached high school that I was exposed to evolution, and once I gained an understanding of the concept, it vastly increased my ability to understand complex relationships in the natural world and allowed me to think critically probably for the first time in my life. Sadly, many of these schools and some public schools continue to teach children these fallacies in an attempt to spread the idea of creationism. When I ask most people who don't accept the theory of evolution as to why they do so, their answer is usually that the bible says otherwise. When I ask them to explain the way they think evolution works, the answers I receive are usually more than amusing. My favorite reply from someone was that, "if evolution were true, why don't we see dogs turning into cats or vice versa today." This ignorance stems from our country's inability to teach evolution on a wide scale, and the fact that many states; particularly those ones which are conservative, who insist on teaching creationism or intelligent design alongside of evolution in science classes.

This map was published as a part of a study done by the U.S. Census Bureau on high school graduation rates on a county-by-county basis across the country. You'll notice that the deepest red counties; those with the lowest graduation rates, occur in much of the deep south and in states which are considered to be deeply conservative. It is in these states where there is a higher push for creationism to be taught alongside evolution in science classes. It also shows that it is in these parts of the country where the uneducated abound, and it is these people which are trying to influence educational policies regarding evolution. I'm not trying to question people's faith here, I'm simply trying to point out that uneducated people are trying to push an unscientific idea; creationism, to be taught on a wide scale to children. As we continue to deplete the world's resources, cause the extinction of wildlife species, and continue to influence climate change, future generations will need people who are well versed in scientific knowledge to help combat increasing environmental and biological challenges. Teaching creationism inhibits a child's ability to think critically, and can even curb their curiosity of the natural world. If life is static; things do not change over time, as is taught in creation, what is the point of studying the natural world at all?  

This is not a failure to understand; it is a refusal to understand. No matter how much evidence continues to be amassed for evolutionary thought, many continue to dismiss the evidence for transitional species such as Archaeopteryx as hoaxes. People are so wrapped up in their religious beliefs and the literal translation of the bible, that they have become so narrow-minded to the point of retarding the minds of 46% of our country's population. Those words are strong, but it is a failure by parents and school systems to supply children with adequate and true scientific knowledge. Do I have a problem with religion? Absolutely not, as long as it does not harm other people either physically or intellectually. In this case, religious beliefs have been passed off as scientific and have made their way into a place where they don't belong. I once saw a bumper sticker that read, "Keep your theology off my biology." I can't think off a phrase that could be any more fitting. We have a magnificent brain, remember to use it.