Latitudinal symbiont zonation in <Emphasis Type="Italic">Stylophora pistillata</Emphasis> from southeast Africa

Studies on latitudinal gradients in Symbiodinium diversity on scleractinian corals are largely restricted to warm-water low latitude locations, and it appears that there is a shift in symbiont distributions with increasing latitude. The Symbiodinium assemblages of high latitude coral communities have largely been undocumented despite occupying an important transitional zone between tropical and temperate regions. Using a combination of the internal transcribed spacer region 2 (ITS2) and denaturing gradient gel electrophoresis (DGGE), we assessed the cladal and subcladal variability of Symbiodinium in the widely distributed species Stylophora pistillata along a latitudinal transect in southeast African waters which extended into high latitude locations. All colonies examined belonged to clade C. Six unique ITS2-DGGE banding profiles (designated C_spa to C_spf) were observed, which showed a latitudinal distribution from north to south, most likely a result of a gradient in water temperature and irradiance driven by riverine input in the southern regions. Sequence analysis revealed that all sequences except one did not match previously identified clade C sub-types, probably due to the lack of regional information in the Western Indian Ocean when compared to the Caribbean and Pacific. This study further supports the applicability of ITS2-DGGE in studies on Symbiodinium diversity, and highlights that potentially ecologically informative biogeographic patterns may be overlooked when only cladal designations are employed.