Genetic differentiation and connectivity of morphological types of the broadcast‐spawning coral Galaxea fascicularis in the Nansei Islands, Japan

Abstract

Population connectivity resulting from larval dispersal is essential for the maintenance or recovery of populations in marine ecosystems, including coral reefs. Studies of species diversity and genetic connectivity within species are essential for the conservation of corals and coral reef ecosystems. We analyzed mitochondrial DNA sequence types and microsatellite genotypes of the broadcast‐spawning coral, Galaxea fascicularis, from four regions in the subtropical Nansei Islands in the northwestern Pacific Ocean. Two types (soft and hard types) of nematocyst morphology are known in G. fascicularis and are significantly correlated with the length of a mitochondrial DNA noncoding sequence (soft type: mt‐L; hard type: mt‐S type). Using microsatellites, significant genetic differentiation was detected between the mitochondrial DNA sequence types in all regions. We also found a third genetic cluster (mt‐L+), and this unexpected type may be a cryptic species of Galaxea. High clonal diversity was detected in both mt‐L and mt‐S types. Significant genetic differentiation, which was found among regions within a given type (F ST = 0.009–0.024, all Ps ≤ 0.005 in mt‐L; 0.009–0.032, all Ps ≤ 0.01 in mt‐S), may result from the shorter larval development than in other broadcast‐spawning corals, such as the genus Acropora. Nevertheless, intraspecific genetic diversity and connectivity have been maintained, and with both sexual and asexual reproduction, this species appears to have a potential for the recovery of populations after disturbance.

Transcriptome profiling of Galaxea fascicularis and its endosymbiont Symbiodinium reveals chronic eutrophication tolerance pathways and metabolic mutualism between partners

“…S10 ). The result presented here confirmed that the 12 corals used in the experiment were from the same lineage and were 100% identical to the sequences of mt-L1 type of Galaxea at GenBank (accession number: LC155810 and AB109376) 8 10 .…”

“…Because of genetic differentiation 8 , their morphological characteristics are correlated with the length of the noncoding region between the mitochondrial genes cytb and nad2 9 . A more recent study reported several cryptic types found in G. fascicularis based on genetic information from microsatellite loci 8 10 . G. fascicularis shows intraspecific genetic diversity and connectivity and appears to have the potential for the recovery of populations after disturbance 8 10 .…”

“…A more recent study reported several cryptic types found in G. fascicularis based on genetic information from microsatellite loci 8 10 . G. fascicularis shows intraspecific genetic diversity and connectivity and appears to have the potential for the recovery of populations after disturbance 8 10 . Additionally, G. fascicularis is relatively resilient to bleaching and sedimentation 11 and is therefore widely used for comparative analyses of coral responses to thermal, acidulated and light stresses 12 13 .…”

Microsatellite markers for multiple Pocillopora genetic lineages offer new insights about coral populations

“…When different genotypes were determined to belong to the same MLL, the most common genotype was assigned 38 . However, if the most common genotype could not be determined ( e.g ., if two genotypes occurred in equal numbers), the genotype was set to zero 39 . We also calculated P SEX to estimate the possibility of coincidence of multilocus genotypes by sexual reproduction, using GenClone ver.…”

Metacommunity ecology of Symbiodiniaceae hosted by the coral Galaxea fascicularis

“…Galaxea fascicularis is a suitable model system to investigate Symbiodiniaceae metacommunity ecology, since it is a widely distributed generalist species acquiring symbionts from the settlement location (Baird et al 2009) and occurs at various depths on the reef. There are several genetic lineages within this species with little morphological differentiation (Nakajima et al 2016). Associations with Cladocopium ITS2 types C1, C1b, C2r, C21, C21a, C27, C3, C3d, C3u, C40, and C161, and Durusdinium types D1, D2, and D17 have been reported (GeoSymbio: Franklin et al 2012, Zhou et al 2012, indicating a rather flexible relationship potentially varying according to exogenous characteristics.…”