"Abundant-center" hypothesis just a myth.

• Position: Ecology

There is little empirical evidence to support a widely held ecological assumption that species are most abundant near the centers of their geographic ranges and decline in number near the ranges' edges, according to a report from Duke University, Durham, N.C. "When we reviewed data from published studies that looked at species abundance at multiple sites across a range, we found almost no evidence that contradicted it," explains Raphael D. Sagarin, associate director for oceans and coastal policy at the Nicholas Institute for Environmental Policy Solutions.

"This is troubling because a lot of current thinking on ecological and evolutionary issues--including how species will respond to climate change, how to identify probable locations of pest outbreaks, how genetic diversity is distributed among populations, and where to locate habitat preserves--has been based on this hypothesis" The validity of these ideas now needs to be re-examined using empirical studies, he stresses.

For their analysis, the researchers reviewed not only published studies, but some new sets of data that they had compiled from field observations in a number of coastal locations of such invertebrate species as sea urchins, sea anemones, and snails. They found that most of the studies showed that patterns of abundance were affected by a complex interplay of environmental...