Abstract

GRAJALES, Alejandro  and  SANCHEZ, Juan Armando. Holobiont assemblages of dominant coral species (Symbiodinium types and coral species) shape Caribbean reef community structure. Rev. acad. colomb. cienc. exact. fis. nat. [online]. 2016, vol.40, n.155, pp.300-311. ISSN 0370-3908.  https://doi.org/10.18257/raccefyn.294.

Research on coral reef community structure suggests that fine spatial-temporal stochasticity drives biodiversity patterns in this tropical marine ecosystem. The combination of a coral colony and its zooxanthella, or holobiont, should therefore be used as the community indivisible units to better understand this structure. Research in zooxanthellae (Symbiodinium) diversity has allowed the identification of specific or generalist host associations. The distribution of specific symbionts depends on both the host identity and the environmental conditions. This study determined the identity on these symbionts within hard corals communities (Scleractinia and Milleporina) at 27 sites on the upper slope habitat (mixed zone) in Cartagena, Colombia (Southwestern Caribbean Sea). Zooxanthellae identification was made with RFLPs analysis (18S, SSU, rDNA), DGGE, and DNA sequencing (ITS2, rDNA). Different combinations of coral species and their specific Symbiodinium types (holobionts) were determined as different ecological units. Taking each holobiont as a variable, a cluster community structure analysis was made and compared to the pattern obtained from using coral species alone. Different site groupings occurred for holobionts and species, where higher similarities were found using holobionts. O. annularis and O. faveolata, two dominant coral species, formed independently different Symbiodinium associations, depending on depth. Their symbiont preference can be under higher selection pressure than previously thought, if they act as different ecological units.

Keywords : Zooxanthellae; community structure; holobiont; Caribbean Sea; coral reefs; Symbiodinium; Scleractinia.

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