Abstract

The critically endangered coral species Acropora palmata and A. cervicornis used to be highly responsible for the structural complexity of Caribbean reefs, providing habitats for an important part of the reef fauna and protection for littoral ecosystems and human infrastructures against erosion. Sadly, since the early 80s, populations have dramatically declined. On the Caribbean scale, most of the previous works investigating Acropora populations genetics and connectivity involved the reefs of Florida, the Bahamas, the Mesoamerican Reef System and the Greater Antilles. Little is known regarding the eastern Caribbean populations, especially in the Lesser Antilles. Here, genetic diversity, structure and connectivity of Acropora populations were investigated using 14 hypervariable microsatellite loci among 42 sampled sites from 11 islands of the Lesser Antilles. A. cervicornis populations revealed to be in decline, that favoured hybridization between A. palmata and A. cervicornis species. Globally, genetic diversity levels in Acropora populations from the Lesser Antilles were lower compared to what was previously reported within the wider Caribbean. For A. palmata, the analysis of the genetic structure, crossed with spatial autocorrelation analysis, revealed an isolation-by-distance pattern at both reef and Lesser Antilles scales. A genetic neighborhood size of c.a. 100 km, and a northward gene flow direction, in agreement with ocean surface currents in the region were found. Altogether, these results suggest a restricted population connectivity and short distance dispersal of Acropora larvae within the Lesser Antilles, further limited by geographic distances among suitable habitat patches. Conservation efforts for these populations would be realized on a local scale, favoring southward populations of the Lesser Antilles.

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