La Jolla, CA (03/16/04)- The traditional classification system used for determining which families coral belong to is out, and DNA taxonomy is in. DNA analyses of dozens of corals in both the Atlantic and Pacific oceans show that many have been misclassified and the old system was wrong.Indeed, some corals found in both oceans thought to be closely related are actually distinct from each other, while others are more closely related than previously believed. These findings, by an international team of researchers, have turned coral taxonomy completely on its head.

"It's important to have them from the nucleus as well as from the mitochondria because they're inherited separately. It gives you two completely independent sources of evidence for evolutionary relationships," Dr. Knowlton said. Researchers selected these specific genes for study because they were known to mutate at a pace that matches the evolutionary history of coral families.

"Some genes change really fast, almost too fast. They keep changing and changing, sort of overwriting the evolutionary signal. In some cases genes change so slowly that even things that have been separated for a long time haven't accumulated enough mutations to tell them apart. We looked long and hard for genes that were changing at the appropriate rate," Dr. Knowlton said.

The large number of samples studied provided an impressive amount of data to support the fact the existing family trees for coral were wrong. Another problem with using the septal teeth as a classification tool is that they are a feature that changes fairly rapidly.

"They keep getting invented over and over again," she said. Rapidly changing features make it difficult to do such detective work. The researchers estimate that the Atlantic and Pacific corals diverged about 34-million years ago.