Fossil Study Helps Pinpoint Extinction Risks for Ocean Animals: When It Comes to Ocean Extinctions, Range Size Matters Most

ScienceDaily (Oct. 23, 2012) — What makes some ocean animals more prone to extinction than others? A new study of marine fossils provides a clue.

An analysis of roughly 500 million years of fossil data for marine invertebrates reveals that ocean animals with small geographic ranges have been consistently hard hit -- even when populations are large, the authors report.

The oceans represent more than 70% of Earth's surface. But because monitoring data are harder to collect at sea than on land, we know surprisingly little about the conservation status of most marine animals. By using the fossil record to study how ocean extinctions occurred in the past, we may be better able to predict species' vulnerability in the future.

"If the patterns we observed in the fossil record hold for species living today, our results suggest that species with large populations but small ranges are at greater risk of extinction than we might have expected," said study co-author Paul Harnik of the National Evolutionary Synthesis Center.

Researchers have long assumed that rare animals are more likely to die out. But "rare" could mean multiple things.

The word "rare" could be applied to species that have restricted geographic ranges, or small populations, or that tolerate a narrow range of habitats, or any combination thereof, the authors say.

Continued:  http://www.sciencedaily.com/releases/2012/10/121023204741.htm