Rare coral cross-breeds to survive

Is it evolution, adaptation, or desperation? Rare species of staghorn corals have apparently started cross-breeding with other, related species of coral in a last-ditch effort to save themselves from extinction.

According to Zoe Richards of the ARC Centre of Excellence for Coral Reef Studies, this "breaks all the traditional rules about what a species is."

The study -- published in the journal PLoS One -- found that the three kinds of Caribbean corals may not actually be the individual species they are currently believed to be. Instead, the study says that Acropora pichoni, Acropora kimbeensis and Acropora papillare are probably hybrids created by cross fertilization.

"Hybridising with another species actually makes a lot of genetic sense if you are rare and the next colony of your species may be hundreds of kilometers away," said Professor David Miller, co-author of the study.

The authors conclude that "Rare Acropora species may therefore be less vulnerable to extinction than has often been assumed because of their propensity for hybridization and introgression, which may increase their adaptive potential."

But this conclusion makes me wonder, when does a species stop being a species? If a species' genes exist, but no pure specimens are alive, has it really saved itself from extinction? Hasn't it really disappeared, and been absorbed into something else? And is this a natural step, or are human activities -- which threaten coral worldwide -- forcing this to happen?

All in all, this study leaves me both encouraged and deeply, deeply troubled.