Comparative Study of Genetic Variability of AAT and CT/GT Microsatellites in Staghorn Coral, Acropora (Scleractinia: Acroporidae)

摘要

Comparative study of genetic variability of AAT and CT/GT microsatellites in staghorn coral, Acropora (Scleractinia: Acroporidae). pg:657-668. Acropora is the most speciose genus of scleractinian corals. However, phylogenies among closely related species and population genetics of Acropora remain equivocal. In this study, 7 AAT-repeat loci developed from the Caribbean species, A. palamta, and 5 dinucleotide (CT/GT)-repeat microsatellites newly developed from the Indo-West-Pacific (IWP) species, A. muricata, were examined to determine their utility for revealing the mutation rate and genetic diversity of Acropora species. Five of the 8 AAT-repeat loci were successfully amplified in IWP species, with DNA sequences in the flanking region showing over 97% similarity to those of the Caribbean species, suggesting homology of these AAT loci among these cross-oceanic Acropora. In contrast, amplifications of all GT-repeat loci failed in the Caribbean species. Eight loci (5 AAT and 3 CT/GT ones) showed Mendefian inheritance based on crossing experiments of A. muricata larvae. When the mutation rate (theta) was estimated, AAT-repeat loci showed relatively higher mutation rates (theta = 39.94-112.82) compared to GT-repeat loci (theta = 2.44-53.33). Analysis of molecular variance indicated a relatively higher within-population variation at AAT-repeat loci (98.6%) than at GT-repeat loci (78.7%). The Fst statistic of 2 sympatric Acropora species (A. muricata and A. digitifera) indicated that the value for AAT loci (Fst= 0.014) was about 15 times lower than that for GT loci (Fst = 0.213), although both microsatellite motifs showed statistically significant differentiation of species. Our study highlights that AAT-repeat loci might have functional constraints and result in underestimating the genetic variability of species and populations; thus, their application to revealing genetic variations within Acropora should be utilized with caution.