Friday, February 06, 2009

Carnival of Science!

The lead story on the BBC New's Science and Environment page is on the research of one of the post-doctoral researchers in my professor's lab. The idea is rather simple, the process was complex.
We know that climate changes over time, and that where one can find a particular type of habitat changes with the climate. Recently, using a wide range of data sources, scientists have been constructing both a detailed history of how climate has changed over time and what climate parameters limit the extent of particular habitats, such as South America's Atlantic Rainforest. My lab-mate, Ana Carnival (along with several collaborators) combined the climate history data with the climate requirement data to make maps of how the extent of the Atlantic forest has changed over the last 20,000 years. She found that there were a few relatively small areas that had been rainforest the whole time, even when climate shifts caused the rest of it to change to other habitat types, such as grassland. She identified these as 'rainforest refugia,' areas where rainforest species could survive through the millenia when the climate was inhospitable elsewhere. She then predicted that these refugia should be the centers from which genetic diversity spread to the rest of the forest once its borders once again grew. To test these predictions, she gathered genetic samples from three species of frogs which can survive only in the rainforest. Sure enough, the frog's DNA told the story she had predicted, confirming the refugia she had identified based on climate models. This is not only cool science, it has significant conservation implications. These refugia should house a large portion of the diversity found in the rainforest, because at some points in the last 20K years, all the rainforest species lived there. This suggests that if we are forced to make choices about which land to preserve (which we are) we might do well to preserve these refugia. And both the methods and the conclusions are potentially generalizable to other thretened habitats around the world.

One final thought: This is very cool work, and very much in line with what most people in my adviser's lab study, but it is so far from my own work that I barely understand the details. This may be why I don't notice any glaring errors in the BBC article, or maybe the UK press are not as bad at writing about science as the American press.


jte said...

Mostly I find it shocking that 20K years is enough time to see as much evolution as is evident in the rainforest. You see things talking about species of insect or fungus or what have you that are native to a mere 1 km^2 or some such. I know the definition of "species" is less than ironclad precise, but still. That's a boat load of evolutionary change in what seems like a short span of time. Isn't the whole issue of people failing to accept evolution that they can't grasp the time scales involved? 20k years is not beyond grasp, I don't think. Except I'm not grasping it!

Dan Levitis said...

The issue isn't that all the evolution that lead to rainforest diverstiy happened in the last 20K years, but rather that much of the local kilometer to kilometer diversity happened that recently. This refugia process actually helps to explain why we see all that local diversity. As long as there is continuous habitat, it is hard for populations to become isolated enough from each other genetically for speciation to occur. When a climate shift divides the forest into lots of little pockets, the population in each of them is likely to be isolated from the others, and free to become genetically distinct. If they become genetically distinct enough, then when the climate shifts back and the forest becomes one again, you might end up with a whole group of closely related species, each in its own part of the forest and all gradually spreading into each other's parts.