Incredible shape-shifting corals, and how they make conservation tough

You can neither tell a book by its cover, nor a coral head by its appearance.

The coral, in fact, might be the stranger of the two, according to research by a team of University of Hawai'i scientists.

Not only can two corals look very different but be essentially the same genetically. But very similar-looking corals can also be very different genetically.

(Image: These two corals from Maui, Porites lobata (yellow) and Porites compressa (bluish-purple), look very different in both color and form, but genetically they are nearly the same. Is one a hybrid or is this coral just very susceptible to different forms? That's not clear. Credit: Zac Forsman.)

The team, Zac H. Forsman and Robert J. Toonen of the Hawai'i Institute of Marine Biology, Daniel J. Barnis of the Zoology Department and Cynthia L. Hunter of the Biology Department, wrote “Shape-shifting corals: Molecular markers show morphology is evolutionarily plastic in Porites,” which appeared in the Biomed Central open access journal Evolutionary Biology. The press release is here.

Corals are now generally identified by their appearance, but the new paper suggests that's not nearly good enough. They expanded standard genetic testing into new areas to try to better understand the corals.

With Porites lutea, which has been treated as a single species, the researchers found that genetically, it could be broken up into at least three distinct genetic groups that the authors say are “deeply genetically divergent.

In other cases, they found that different-looking corals with, say, a branching appearance or a mounding appearance, were almost impossible to tell apart at the genetic level—like the two species pictured above.

In part, this means that some corals that you'd expect to be quite distinct may actually be capable of interbreeding. And some species may just be real shape-shifters, inherently capable of taking different looks.

That has a number of impacts.

One is that you might have assumed a unique-looking coral in a given environment was endemic or unique to that locale. But in fact, it might simply be just another a natural form of that coral.

And other corals, which might look the same in different locations, might actually represent unique adaptations.

“This ‘coral species problem’ is an impediment to understanding the evolution and biodiversity of this important and threatened group of organisms,” the authors write.

In a challenging environmental age, in which coral reefs are threatened by warming oceans, by rising waters, by pollution, by alien species invasions and more, this makes it all the more difficult to develop strategies to protect the corals.

Indeed, until you can accurately tell one coral from another, or identify siblings, your reef could be experiencing change or losing things without you knowing it.

In the words of the scientists: “Species definitions based solely on evolutionarily labile, polymorphic, or phenotypically plastic traits are likely to be misleading and confound attempts to identify, understand, and conserve coral biodiversity or to recognize its loss.”

©2009 Jan TenBruggencate