Environmental latitudinal gradients and host‐specificity shape Symbiodiniaceae distribution in Red Sea Porites corals

Abstract

Aim The aim of the study was to assess the diversity of algal symbionts of the family Symbiodiniaceae associated with the coral genus Porites in the Red Sea, and to test for host‐specificity and environmental variables driving biogeographical patterns of algal symbiont distribution. Location Saudi Arabian Red Sea. Taxon Endosymbiotic dinoflagellates of the family Symbiodiniaceae in association with the reef‐building coral genus Porites. Methods Eighty Porites coral specimens were collected along the Saudi Arabian Red Sea coast. Species boundaries were assessed morphologically and genetically (putative Control Region – mtCR; ITS region – ITS). Community composition of symbiotic dinoflagellates of the family Symbiodiniaceae was also assessed. Using the ITS2 marker with the SymPortal framework, Symbiodiniaceae data at the genus, majority ITS2 sequence and ITS2 type profile were used to assess symbiont diversity and distribution patterns. These were analysed in relation to coral host diversity, geographic location and environmental variables. Results Among the 80 Porites samples, 10 morphologies were identified. These corals were clustered into five lineages (clades I–V) by each of the markers independently. Clades I, II and III each comprised of a single Porites morphology, while clades IV and V contained up to five distinct morphologies. The diversity of Symbiodiniaceae associated with Porites was high and latitudinal differentiation was observed. In particular, a shift from a Cladocopium‐dominated to a Durusdinium‐dominated community was found along the north–south gradient. Symbiont diversity showed the patterns of geographic‐specific association at Symbiodiniaceae genus, majority ITS2 sequence and ITS2 type profile level. Specific associations with host genotypes (but not morphological species) were also recovered when considering Symbiodiniaceae majority ITS2 sequence and ITS2 type profiles. Main conclusions This study provides the first large‐scale molecular characterization of Symbiodiniaceae communities associated with Porites corals from the Saudi Arabian Red Sea. The use of intragenomic diversity data enabled the resolution of host‐symbiont specificity and biogeographical patterns of distribution, previously unachievable with the ITS2 marker alone. Finally, correlation among symbiont diversity and Red Sea environmental gradients was documented.

Fine-scale delineation of Symbiodiniaceae genotypes on a previously bleached central Red Sea reef system demonstrates a prevalence of coral host-specific associations

“…As delineations of coral-Symbiodiniaceae associations continue to be conducted at more fine-scale resolutions, high-fidelity associations as seen here continue to be resolved (Smith et al 2017;Lewis et al 2019;Terraneo et al 2019). Such characterizations evidence a considerable pool of phenotypically distinct associations upon which mechanisms of adaptation may act and build upon the considerable evidence pointing toward a prevalence of host specificity within the Symbiodiniaceae (Santos et al 2004;Smith et al 2017;Thornhill et al 2017).…”

“…Our use of the SymPortal pipeline in conjunction with relatively deep NGS amplicon sequencing has enabled fine-scale resolutions of Symbiodiniaceae communities and genotypes in the Thuwal reef system. Resources to which these resolutions may be directly compared are limited (but see Gardner et al 2019;Terraneo et al 2019;Camp et al 2020) given the only recent availability of such analytical approaches (approaches able to appropriately handle Symbiodiniaceae intragenomic ITS2 variability), but some genotypes may be related to previous resolutions if ITS2 intragenomic characteristics have been utilized. For example, the definitions of C. thermophilum or multiple Durusdinium species all include ITS2 intragenomic characterizations (LaJeunesse et al 2014;Hume et al 2015).…”

Homogenization of Endosymbiont Communities Hosted by Equatorial Corals during the 2016 Mass Bleaching Event

“…For the last decade, high-throughput sequencing has been a mainstream technique for characterizing coral endosymbionts [ 9 , 75 , 107 , 108 ]. Most recently, development of the SymPortal analytical framework specifically for the processing of ITS2 amplicon data obtained from HTS has allowed us to characterize Symbiodiniaceae communities at a much finer resolution by accounting for intragenomic ITS2 diversity [ 81 , 109 , 110 ]. Overall, we found qPCR and HTS to produce consistent patterns of relative Durusdinium and Cladocopium abundances ( Figure 2 ), even though the relationship between relative qPCR-estimated concentrations and HTS read abundances was weak ( Figure S1 ).…”

Host age is not a consistent predictor of microbial diversity in the coral Porites lutea

“…Species identification of each colony was confirmed via a combination of in situ colony and corallite photographs, as well as observations of the ventral triplet septal arrangement performed under a stereo microscope according to Veron 51 and Forsman et al 52 . Analyses indicated that all collected specimens were of one species putatively identified as Porites lutea 53,54 .…”