Coral reefs are "hotspots" of biodiversity that harbor thousands of species in their tiny cracks and crevices, according to our partner The Conversation.
Despite its resemblance to the pink lace coral of the Caribbean, the one from the coasts of Brazil is so different that it should be considered a new species.
This analysis was conducted by
Flavia Nunes
, researcher in evolutionary ecology at the French Research Institute for the Exploitation of the Sea (Ifremer).
The little pink lace coral in the illustration photo is well surrounded, certainly by his family.
The lace coral does not disperse very far and often settles next to its relatives – unlike its cousins, the reef-building corals, which can disperse great distances thanks to their larvae.
By always staying close to home, each lace coral population ends up reproducing with a restricted circle.
By remaining isolated, a population can become a new species over time.
This is the case for the pink lace coral off the coast of Brazil, of which a hitherto unknown species has just been identified in a study recently published in the journal
Coral Reefs
.
Coral reefs are “hotspots” of biodiversity: they are home to thousands of species in the small cracks and crevices of the reef.
Lace corals contribute to this diversity by favoring the establishment of associated species.
How are new coral species born?
To understand the evolution of lace corals in the Atlantic, we studied 18 lace coral populations in the Caribbean, Brazil and Africa.
Remarkably, each population had its own genetic variants, quite distant from each other.
To achieve such genetic differentiation, very little exchange of larvae or individuals had to take place.
In the marine environment, many organisms stay connected to other members of their tribe through the dispersal of larvae.
They can emit their reproductive cells into the water column, allowing them to reproduce with individuals who are not necessarily nearby.
The larvae then develop in the water column and can swim for several days to several weeks, sometimes landing hundreds of kilometers from their home reef.
When they become adults, they will probably breed with individuals from elsewhere.
This is how hard corals reproduce: populations separated by hundreds of kilometers maintain “connectivity” and are genetically similar.
Lace coral larvae crawl, but do not swim
Lace corals do not reproduce in this way.
So far, only the reproductive behavior of a few lace coral species has been studied.
What we do know is that fertilization is internal, not in the water column.
Once the fertilized eggs have hatched and a larva is ready to leave its parent, it does not swim, it crawls… which limits the distance traveled.
Most of the larvae thus settle in the original reef, sometimes even right next to their parents.
This lack of connectivity, or exchange of larvae and individuals between populations, is exactly what leads to the isolation necessary for the origin of new species.
Without the exchange of genetic information, all the tribes become more and more singular over time, until they no longer belong to the same species, and they can no longer reproduce among themselves.
Despite its resemblance to the pink lace coral of the Caribbean, the one from the coasts of Brazil is so different that it should be considered a new species.
Using a “molecular clock” – a technique that estimates the time elapsed between two species by counting the number of mutations between them – it is estimated that the pink lace corals of the Caribbean and Brazil have become distinct species about eleven million years ago, around the time the Amazon River was created.
OUR “CORAL” FILE
Given the few exchanges observed for the pink lace coral, if the mode of reproduction is similar in other species, it is likely that many other "hidden" species remain to be discovered.
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