BOB HIRSHON (host):
A new look at an old rule. I’m Bob Hirshon and this is Science Update.
Scientists have long known that animals grow larger at high latitudes than they do closer to the Equator. Now, University of Houston ecologists Steven Pennings and Chuan-Kai Ho have a new explanation. Pennings had already learned that herbivorous insects prefer plants from high latitudes over the same plants from low latitudes.
STEVEN PENNINGS (University of Houston):
It turns out that their preferences actually are revealing differences in the quality of the food – that the high-latitude food is better.
Now, Pennings and Ho report that three different herbivores all grew bigger on a diet of high-latitude plants than on a lower-latitude diet. Pennings says that the plants from cold climates appear to have more nitrogen, which makes them more nutritious, and have fewer toxic defense chemicals. They’re also softer and easier to eat. And it may be that bigger herbivores make the predators that eat them bigger too. I’m Bob Hirshon for AAAS, the Science Society.