Magazine article Science News

Another Clue to Where the Species Are

Magazine article Science News

Another Clue to Where the Species Are

Article excerpt

From Greenland to Guatemala, Antarctica to Africa, one of the most striking and consistent patterns of life on this planet is the greater profusion of species the farther one gets from the poles. Though the pattern may be obvious, the explanation for it is not-climate, available space, and the vagaries of geologic history have all entered into discussions of species richness, with no clear resolution.

Several analyses, particularly a large-scale study in 1991 of species richness in North America, have focused on energy as the key. Closer to the equator, more solar energy is available for photosynthesis, the first link in the food chain.

A new statistical analysis of the data from that study has come up with an interesting twist: The energy explanation applies only about as far south as the Canadian-U.S. border. For the rest of the continent, at least for distributions of mammal species, local differences in habitat exert the greater influence.

"The energy-species richness relationship breaks down in warm regions," says biologist Jeremy T. Kerr of York University in North York, Ontario. Kerr and York biologist Laurence Packer report their findings in the Jan. 16 Nature. The researchers noticed a marked change in the scatter of data points on a graph relating mammal species richness to potential evapotranspiration, a measure of energy based on how much water would evaporate from a surface. The change corresponds to a zone just south of the Canadian-U. …

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