Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Thursday, June 01, 2006

Cooking up a species

Here's one I was going to leave until I could read the actual paper, because I am both suspicious and skeptical on the one hand and sympathetic to the underlying rationale on the other. And on the gripping hand...
Writing this week in the Proceedings of the National Academy of Sciences, scientists say higher temperatures near the equator speed up the metabolisms of the inhabitants, fueling genetic changes that actually lead to the creation of new species.

The finding — by researchers from the University of Florida, the National Center for Ecological Analysis and Synthesis, Harvard University and the University of New Mexico at Albuquerque — helps explain why more living species seem to exist near the equator, a scientific observation made even before naturalist Charles Darwin set sail to South America on the H.M.S. Beagle nearly two centuries ago.

It may also have a bearing on concepts such as global warming and efforts to preserve diversity of life on Earth.

“We’ve shown that there is indeed a higher rate of evolutionary change in the form and structure of plankton in the tropics and that it increases exponentially because of temperature,” said James Gillooly, an assistant professor of zoology with the UF Genetics Institute. “It tells us something about the fundamental mechanisms that shape biodiversity on the planet.”

Speciation — when animals or plants actually evolve into a new species — occurs when life forms with a common ancestor undergo substantial genetic change.

Using a mathematical model based on the body size and temperature-dependence of individual metabolism, the researchers made specific predictions on rates of speciation at the global scale. Then, using fossils and genetic data, they looked at rates of DNA evolution and speciation during a 30-million-year period in foraminifera plankton, a single-celled animal that floats in the ocean. Researchers compared arrivals of new species of this type of plankton with differences in ocean temperatures at different latitudes ranging from the tropics to the arctic. The results agreed closely with predictions of their model.
There are many errors in this release, not the least being the definition and explanation of a new species, but one ought not attack scientists for the inability of a journalist (or in this case, PR maven) to express themselves properly.

The sympathy I have is that there truly must be an energy budget involved in speciation. Life is, after all, applied thermodynamics, but there is something (please excuse me!) fishy about this. The thermodynamic budget of a species will depend entirely upon context - its trophic level (position in the food web), the complexity of the ecosystem, its distribution and abundance. You can't tell me that a population of 10,000 fishes speciating over time is energetically equivalent to 100 million fishes of the same overall body size speciating. The energetic cost to speciation depends crucially on a number of individual and contingent parameters.

But, as I say, I'll have to wait to see the paper. Last time I looked it wasn't there, either in this week's edition or early edition.