Molecular ecology of Lophelia pertusa in the NE Atlantic

Abstract

During the ACES (Atlantic Coral Ecosystem Study) European Programme, various molecular methods were used to assess the genetic diversity of deep-water corals, by focusing on Lophelia pertusa, the main reef-building species in the northeast Atlantic. Investigations at a high taxonomic level aimed at understanding the evolutionary history of azooxanthellate corals by placing them in the phylogenetic tree of scleractinian corals, using partial sequences of the mitochondrial 16S region. The taxonomy of L. pertusa was consistent with morphological studies at the family level. However, eastern and western Atlantic specimens were genetically highly differentiated. Madrepora oculata was found to be incorrectly classified by morphological analysis. Intraspecific analyses were undertaken for L. pertusa, using specific microsatellite markers, to screen individuals collected at 10 different sampling sites, distributed along the European margin and in Scandinavian fjords. Sequencing of the ribosomal Internal Transcribed Spacer (ITS) 1 and 2 nuclear DNA regions was used as a complementary method. Both microsatellite and gene sequence data showed that L. pertusa is not constituted by one panmictic population in the northeast Atlantic, but instead forms distinct, offshore and fjord populations. Along the continental slope, the subpopulations are moderately differentiated. Although larvae might be dispersed along the European margin, the gene flow occurring among these subpopulations is likely to be sporadic, and must be considered in the light of the age of these coral communities, the prevalence of asexual reproduction in the development of the reefs and the longevity of individual clones. Inbreeding was shown at several sites, suggesting a high degree of self-recruitment. The level of genetic diversity and the contribution of asexual reproduction to the maintenance of the subpopulations were highly variable from site to site. These results are of major importance in the generation of a sustainable management strategy for these diversity-rich deep-sea ecosystems.