Abstract
The reef-building, scleractinian coral, Galaxea fascicularis, is classified into soft and hard types, based on nematocyst morphology. This character is correlated with the length of the mitochondrial non-coding region (mt-Long: soft colony type, and nematocysts with wide capsules and long shafts; mt-Short: hard colony type, and nematocysts with thin capsules and short shafts). We isolated and characterized novel polymorphic microsatellite markers for G. fascicularis using next-generation sequencing. Based upon the mitochondrial non-coding region, 53 of the 97 colonies collected were mt-Long (mt-L) and 44 were mt-Short (mt-S). Among the 53 mt-L colonies, 27 loci were identified as amplifiable, polymorphic microsatellite loci, devoid of somatic mutations and free of scoring errors. Eleven of those 27 loci were also amplifiable and polymorphic in the 44 mt-S colonies; these 11 are cross-type microsatellite loci. The other 16 loci were considered useful only for mt-L colonies. These 27 loci identified 10 multilocus lineages (MLLs) among the 53 mt-L colonies (N MLL/N = 0.189), and the 11 cross-type loci identified 7 MLLs in 44 mt-S colonies (N MLL/N = 0.159). Significant genetic differentiation between the two types was detected based on the genetic differentiation index (F ST = 0.080, P = 0.001). Bayesian clustering also indicated that these two types are genetically isolated. While nuclear microsatellite genotypes also showed genetic differentiation between mitochondrial types, the mechanism of divergence is not yet clear. These markers will be useful to estimate genetic diversity, differentiation, and connectivity among populations, and to understand evolutionary processes, including divergence of types in G. fascicularis.
Highlights
Coral reef biodiversity estimates require unambiguous definitions of reef-building coral species because these constitute the structure of the reefs and they are increasingly endangered by both global and local disturbances
We characterized one population based on the ratio of mitochondrial types and investigated clonality of each mitochondrial type and genetic differentiation between mitochondrial types within that population
From the non-coding region between cyt b and nad 2, 53 colonies from Zampa were identified as mt-L while 44 were categorized as mt-S
Summary
Coral reef biodiversity estimates require unambiguous definitions of reef-building coral species because these constitute the structure of the reefs and they are increasingly endangered by both global and local disturbances. Galaxea fascicularis (Linnaeus, 1767) cannot be mistaken for any other species It is widely distributed [2], and is one of the dominant coral species in reefs around Okinawa, Japan. For G. fascicularis, Suzuki et al (unpublished data) developed five microsatellite markers (GenBank accession number: AB272099-AB272103), and Chen et al [12] attempted to characterize the markers using colonies from two Chinese populations. Two of these loci showed significant deviation from Hardy-Weinberg equilibrium (HWE) in both populations. We characterized one population based on the ratio of mitochondrial types and investigated clonality of each mitochondrial type and genetic differentiation between mitochondrial types within that population
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