Marine biologists fear for corals, since climate change will dramatically effect their habitats. However, corals may be more resilient than we’ve given them credit for. Rare corals, one thought to be the most vulnerable to extinction, may be able to hybridize to save themselves according to a study recently published in PLoS One.
Hundreds of species of corals are on the IUCN’s red list of threatened species. Because rarer species of corals have fewer mating opportunities, they have lower genetic diversity and high levels of inbreeding, so it is assumed they are at a much higher risk of extinction.
However, when faced with a shortage of same-species mates, rarer species of Acropora (Staghorn Corals) may be able to cross-breed with other species. The evidence lies in the genes of several rare species of coral, which scientists at the ARC Centre of Excellence for Coral Reef Studies found to be hybrids. This means that these species may be able to survive climate change after all, for they can draw upon the genetic diversity of other species to adapt. This study is the first to firmly show that they can cross-fertilize and grow.
How the corals interbred isn’t clear, but what is known is that the corals have the ability to break species boundaries. This is particularly good news because Acropora corals are one of the most important reef-building corals in the Indian and Pacific Oceans, with rarer species occupying the fringes of where corals grow. WIthout the rare species, coral cover would be lost in the deepest and shallowest areas that corals live.
It is even possible that the rare corals of today, rather than being leftovers from once-common species, are actually the genetic pioneers. If this is true, the species we deem ‘rare’ may end up being widespread, as they may hold the key to corals surviving the damage done by humans and climate change.
The discovery is a rare but refreshing bit of good news in a field where calamity, doom and gloom are the norm.
Okay, help me out here.
This is great, and I’m no expert. But hybrids are (usually) sterile, so, in effect, evolutionary dead-ends, and do not fit the definition of a species – an interbreeding population that produces fertile progeny. So I’m wondering (but I don’t know) that these corals, being colony organisms, are, strictly speaking, not fully evolved into separate species. That they have, in order to allow for the overcoming of environmental eventualities such as they are facing, evolved to keep their evolution in check, so to speak. So are they actually crossing species boundaries? Or do we have to re-think how we define species?
From what I can tell, they were previously classified as separate ‘species’ for physiological reasons including breeding, but are now revealed to be genetic hybrids of other, more common species, thus the ‘rethink species boundaries’ is probably accurate – however, these species, as far as we know, aren’t currently interbreeding with species they hybridized from. So the question becomes when and why do species of corals hybridize to form new species? And what does this mean for coral diversity and evolution?