Les coraux du genre Acropora dans les Petites Antilles : approches génétiques, écologiques et de conservation

Coral reefs which present a high biodiversity are threatened. Branching corals such as Acropora species are highly responsible for the structural complexity of coral reefs providing habitats for an important part of the reef fauna and protection for littoral ecosystems and human infrastructures against erosion. The two Caribbean Acropora species (A. palmata and A. cervicornis) are nowadays critically endangered. That is why it is crucial to estimate resilience capacities of Acropora populations to define appropriate conservation strategies, particularly in the Lesser Antilles region that is poorly studied. A. cervicornis populations revealed to be in decline. That favoured hybridization between A. palmata and A. cervicornis species. This hybrid was described as A. prolifera (Lamarck, 1816). In comparison with other Caribbean populations, A. cervicornis and A. palmata presented a lower genetic diversity in the Lesser Antilles. An isolation by distance pattern, a limited connectivity and a likely northward genic flow were revealed. Conservation efforts for these populations would be realized at a local scale, favouring southward populations of the Lesser Antilles. The study of symbiotic algal communities of these corals revealed a dominant association with the A3 sub-clade and important variations in the density of symbionts. Finally, the culture of coral fragments seems to be possible even if it does not prove that colonies could be maintained and participate to reproduction events after transplantation.

Key-words: Acropora palmata, Acropora cervicornis, threatened species, Symbiodinium, Lesser Antilles, hybridization, population genetics, coral culture