In the wake of European exploration and settlement of the New World, waves of infectious disease decimated Native Americans. Exact numbers will never be known but many millions surely died in what was in all likelihood the worst demographic catastrophe in human history. The culprits were the many Old World diseases unintentionally brought to the New World by Europeans. Chief among these was smallpox but many other examples are known (malaria, cholera, influenza, etc.). Native Americans had no exposure to these diseases and for historical reasons were also more uniform genetically speaking that Old World peoples.
The amphibian equivalent of smallpox is playing itself out in our own times. The pathogen is a fungus called Batrachochytrium dendrobatidis (Bd for short) and it can cause a disease called chytridiomycosis in frogs, salamanders and caecilians (the three groups of living amphibians). To the best of our understanding, this is an African amphibian disease that was unintentionally transported out of Africa when African clawed frogs (Xenopus) were widely used as a human pregnancy test in the mid-20th century. Now amphibians from all over the world are being exposed to this novel disease and in many places are dying in droves. In fact, dozens of species (primarily in Australia and South and Central America) are thought to have been completely annihilated (driven to extinction) by this fungus. This is thought to be the first documented case of a pathogen causing an extinction, ever. For reasons that are just beginning to be understood, other species and other regions seem immune or less affected.
Many questions remain but in the meantime those who love amphibians are trying desperately to prevent additional extinctions by captive breeding vulnerable species and using other strategies. Unfortunately, there is no “putting the genie back in the bottle” as the fungus has been spead far and wide. This just yet one more example of how unintentional human actions can have dramatic, unanticipated and long-lasting impacts on other life forms.
The new semester has started at the College of Wooster and invariably some of the new students and faculty are curious about the black squirrels that are common around our campus. So, what’s the deal? Here goes: the black squirrels are the same species as the gray ones (Sciurus carolinensis – the eastern gray squirrel) but possess a certain form of a gene that colors their fur black. Less than two years ago, a research team in the UK identified the specific form of the gene that causes the different pigmentation (at least in UK gray squirrels, which were introduced there in the 19th century from North America and now are associated with the decline of Britain’s native squirrels). Many other mammals also have melanistic forms (i.e., all black individuals: wolves, pigs, mice, jaguars, etc.). For some reason, the black squirrels are fairly localized (they only occur in certain areas) but are often common where they do occur. Recent surveys on our campus have shown that black individuals outnumber the gray ones by about a 3:1 margin, on average. The black and gray ones do mate and produce offspring with one another.
So, in a nutshell(!) – that’s the deal with the black squirrels!
(Note that there are two other squirrel species on campus, too. The fox squirrel (Sciurus niger) is larger, has a rusty orange belly and is sometimes seen amongst the gray squirrels but is less common. The red squirrel (Tamiasciurus hudsonicus) is rarely seen and is usually associated with hemlock trees, especially near the President’s house.)
I recently returned from a research trip to Trinidad and Tobago. Five undergraduates and myself spent 10 days based out of Charlotteville (Tobago) working on projects on frog ecology, evolution and conservation. We got up early, stayed up late and ate many mangoes and fried plantains. Stephanie Andrus, Travis Calkins, Aaron Novick, Alex Vanko and Ned Weakland (all COW class of ’12) worked hard to help advance our knowledge of Caribbean frogs. More to come….
I’m putting together a new website. It’s frustrating but hopefully will be worth the time! Enjoy the pictures.