Asexual reproduction in bad times? The case of Cladocora caespitosain the eastern Mediterranean Sea

We analysed the patterns of genetic variabilityof eastern Mediterranean populations of the scleractinian coral Cladocora caespitosa, from the Aegean and Levan-tine seas, using 19 polymorphic microsatellite loci, 11 ofwhich were newly characterized. The observed genetic pattern reflects a scenario of isolation by environment: FST comparisons showed a higher degree of genetic differentiation between the two Cypriot populations that are separated by only 11 km than between these two Levantine populations and the Aegean population in Greece, whichare separated by 1300 km. We hypothesize that local-scale oceanographic factors influenced the dispersal of planulae between the geographically close populations, playing acrucial role in the genetic structure of this coastal coral.Yet, despite being characterized as a species with limited dispersal and high self-recruitment, large-scale migrationdoes eventually occur as first-generation migrants wereidentified between the most distant populations. In linewith previous findings of reproductive plasticity in C.caespitosa, we also found localized differences in reproduction mode (sexual vs. asexual) within a geographically limited context. Several individuals were identified asclones, indicating the predominance of asexual reproduction in one of the Cypriot populations. We interpret this predominance either as a direct response to or as an indirectconsequence of perturbations suffered by thisC. caespitosapopulation. These perturbations are caused by unfavourable environmental conditions that threatened local sur-vival, in particular water temperature changes andwindstorm swells. Asexual reproduction may be a mecha-nism used byC. caespitosato counteract mortality eventsand recolonize devastated areas, and likely accounts for the occasional high levels of clonality and low levels of genetic diversity. Local adaptations such as these should thereforebe considered in conservation and management strategiesto maintain and preserve the