Spatial and temporal genetic structure of Symbiodinium populations within a common reef-building coral on the Great Barrier Reef

The dinoflagellate photosymbiont Symbiodinium plays a fundamental role in defining the physiological tolerances of coral holobionts, but little is known about the dynamics of these endosymbiotic populations on coral reefs. Sparse data indicate that Symbiodinium populations show limited spatial conne...

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Published in:	Molecular ecology Vol. 22; no. 14; pp. 3693 - 3708
Main Authors:	Howells, Emily J., Willis, Bette L., Bay, Line K., van Oppen, Madeleine J. H.
Format:	Journal Article
Language:	English
Published:	Oxford Blackwell Publishing Ltd 01-07-2013 Blackwell
Subjects:	Acropora millepora Animals Anthozoa - genetics Anthozoa - physiology Biological and medical sciences Biological evolution Cnidaria. Ctenaria connectivity coral Coral Reefs Dinoflagellida - genetics Dinoflagellida - physiology disturbance DNA, Ribosomal - genetics Fundamental and applied biological sciences. Psychology Genetic diversity Genetics of eukaryotes. Biological and molecular evolution Invertebrates Marine biology Microsatellite Repeats - genetics population Population Dynamics Population genetics Population genetics, reproduction patterns Scleractinia Symbiodinium Symbiosis Symbiosis - genetics zooxanthellae Australia Oceania Great Barrier Reef ISEW, Australia, Queensland, Great Barrier Reef zooxanthellae Protozoa disturbance Coral reef Perturbation Population genetics Symbiodinium population Coelenterata connectivity Coral Cnidaria Invertebrata coral
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Summary:	The dinoflagellate photosymbiont Symbiodinium plays a fundamental role in defining the physiological tolerances of coral holobionts, but little is known about the dynamics of these endosymbiotic populations on coral reefs. Sparse data indicate that Symbiodinium populations show limited spatial connectivity; however, no studies have investigated temporal dynamics for in hospite Symbiodinium populations following significant mortality and recruitment events in coral populations. We investigated the combined influences of spatial isolation and disturbance on the population dynamics of the generalist Symbiodinium type C2 (ITS1 rDNA) hosted by the scleractinian coral Acropora millepora in the central Great Barrier Reef. Using eight microsatellite markers, we genotyped Symbiodinium in a total of 401 coral colonies, which were sampled from seven sites across a 12‐year period including during flood plume–induced coral bleaching. Genetic differentiation of Symbiodinium was greatest within sites, explaining 70–86% of the total genetic variation. An additional 9–27% of variation was explained by significant differentiation of populations among sites separated by 0.4–13 km, which is consistent with low levels of dispersal via water movement and historical disturbance regimes. Sampling year accounted for 6–7% of total genetic variation and was related to significant coral mortality following severe bleaching in 1998 and a cyclone in 2006. Only 3% of the total genetic variation was related to coral bleaching status, reflecting generally small (8%) reductions in allelic diversity within bleached corals. This reduction probably reflected a loss of genotypes in hospite during bleaching, although no site‐wide changes in genetic diversity were observed. Combined, our results indicate the importance of disturbance regimes acting together with limited oceanographic transport to determine the genetic composition of Symbiodinium types within reefs.
Bibliography:	ark:/67375/WNG-8F6RNNQW-2 istex:52FEBED69C3F992F642B10CDEA624537633C7BFB Fig. S1 Bayesian information criterion used to select the number of clusters used in the discriminant analyses of principal components to examine the assignment of Symbiodinium C2 microsatellite alleles hosted by Acropora millepora to genetic clusters. Fig. S2 Genetic structure of Symbiodinium C2 populations among sites, years and the bleaching status of Acropora millepora hosts at 7 sites in the Palm Islands, Great Barrier Reef using a partial data set of a subset of loci from which single alleles were recovered from Symbiodinium cultures. Fig. S3 Population wide genetic diversity of Symbiodinium C2 among sites, years and the bleaching status of Acropora millepora hosts at the Palm Islands, Great Barrier Reef. Table S1 Frequency of microsatellite alleles within Symbiodinium C2 populations hosted by Acropora millepora at the Palm Islands, Great Barrier Reef. Table S2 Frequency of a subset of microsatellite alleles within Symbiodinium C2 populations hosted by Acropora millepora at the Palm Islands, Great Barrier Reef. Table S3 (a) Analysis of variation of Symbiodinium C2 genetic diversity within individual colonies (allelic richness) and populations (% of alleles per locus) among sites, years and the bleaching status of Acropora millepora hosts at the Palm Islands, Great Barrier Reef. (b) Fishers LSD post-hoc P values for comparisons of Symbiodinium C2 genetic diversity within individual colonies among sites, years and the bleaching status of Acropora millepora hosts at the Palm Islands, Great Barrier Reef. P values in bold face indicate significance at α = 0.05. N = normally pigmented, B = bleached. Table S4 (a) Analysis of a partial data set of microsatellite alleles at a subset of loci from which single alleles were recovered from Symbiodinium cultures. Analysis of variance was used to partition Symbiodinium C2 genetic variation among sampling years (1997, 2004 and 2009) and sites for populations hosted by Acropora millepora at the Palm Islands, Great Barrier Reef. (b) Pairwise estimates of Symbiodinium C2 genetic differentiation among sampling years and sites for populations hosted by Acropora millepora at the Palm Islands, Great Barrier Reef. Φ values (above the diagonal) indicate the magnitude of genetic differentiation between populations, and P values (below the diagonal) in bold face indicate significance after sequential Bonferroni correction at α = 0.05. Table S5 (a) Analysis of a partial data set of microsatellite alleles at a subset of loci from which single alleles were recovered from Symbiodinium cultures. Analysis of variance was used to partition Symbiodinium C2 genetic variation among sites and the bleaching status of Acropora millepora hosts in 2009 at the Palm Islands, Great Barrier Reef. (b) Pairwise estimates of Symbiodinium C2 genetic differentiation among sites and the bleaching status of Acropora millepora hosts at the Palm Islands, Great Barrier Reef. Φ values (above the diagonal) indicate the magnitude of genetic differentiation between populations, and P values (below the diagonal) in bold face indicate significance at α = 0.05 following sequential Bonferroni correction. N = normal pigmentation, B = bleached. ArticleID:MEC12342 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0962-1083 1365-294X
DOI:	10.1111/mec.12342