Population genetic structure of the stony coral Acropora tenuis shows high but variable connectivity in East Africa

Abstract

Aim The aim of this study is to determine the genetic diversity, population structure and connectivity of the broadcast-spawning coral Acropora tenuis (Cnidaria; Scleractinia; Acroporidae). Based on the long pelagic larval duration(PLD) of the species, long-distance dispersal resulting in high connectivity among populations is hypothesized.Location East Africa (Kenya and Tanzania; 2.5°S~10°S)Methods A total of 269 samples were collected from 11 sample sites in Kenyaand Tanzania spanning a distance of 900 km. The coral fragments were geno-typed using seven microsatellite markers. Analyses included population genetic estimations of diversity and population differentiation, principal coordinate analysis (PCoA), Bayesian clustering approaches and testing for isolation by distance (IBD).Results Moderate, but significant, genetic structure was found when compar-ing all sample sites, but IBD could not be detected. Based on Bayesian cluster analyses three groups of samples sites could be identified: (1) Kenya and north-ern Tanzania, (2) southern Tanzania and (3) sample sites located in the Zanz-ibar and Pemba channels.Main conclusions High connectivity can be explained by the long-distance dis-persal capacity ofA. tenuisand by the influence of the northbound East AfricanCoastal Current facilitating dispersal by effectively spreading larvae along the coast.Oceanographic characteristics rather than distance are factors that determine con-nectivity among populations ofA. tenuisin Kenya and Tanzania. No clear genetic break was identified. However, variable connectivity between sample sites does occur, with limited connectivity of the sample sites Misali and Stonetown