Sea surface temperatures (SST) and chlorophyll a concentrations (Chl a) in the southern Red Sea have wide variations based on distance from the coast. To understand how these variations can affect the diversity of symbionts hosted by reef-associated organisms, we conducted a study in the central and southern Red Sea to examine the diversity of Symbiodiniaceae hosted by the zooxanthellate zoantharian Palythoa tuberculosa at different distances from the coast: offshore (FBO), midshelf (FBM) and inshore (FBI) of Farasan Banks, and inshore at Thuwal (TI). Genomic DNA was extracted from 198 specimens, followed by amplification of the ribosomal DNA internal transcribed spacer 2 (ITS-2) and noncoding region of the chloroplast plastid minicircle (psbAncr). Durusdinium and six lineages of Cladocopium (Pt-1-a, Pt-1-b, Pt-1-c, Pt-1-d, Pt-3-a, Pt-3-b) were identified based on sequences of the two marker regions. Changes in composition of Symbiodiniaceae lineages were observed from FBI (high SST, high Chl a) to FBO (low SST, low Chl a). Molecular variance analyses showed that distance from coast was the most likely predictor of differences in Cladocopium lineages. Multinomial logistic regression analysis showed a transition among different Cladocopium lineages as SST increased. One Cladocopium lineage, Pt-1-b, demonstrated higher prevalences at high SSTs and increased in prevalences at the same rate as thermotolerant Durusdinium. Additionally, Cladocopium lineage Pt-3-a had a high affinity to low Chl a concentrations. This study demonstrates that environmental variations in SSTs and Chl a concentrations are significant predictors for the diversity of dominant Symbiodiniaceae within individual host P. tuberculosa colonies. We theorize that flexibility with different lineages of Symbiodiniaceae allows generalist P. tuberculosa to live across a wide range of environments in the southern Red Sea.

中文翻译：

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环境因素对红海中南部结核菌共生科多样性的影响

红海南部的海面温度 (SST) 和叶绿素 a 浓度 (Chl a) 因距海岸的距离而有很大差异。为了了解这些变化如何影响珊瑚礁相关生物寄宿的共生体多样性，我们在红海中部和南部进行了一项研究，以检查距海岸不同距离的虫黄藻类动物 Palythoatuberculosa 寄居的共生菌科的多样性：近海(FBO)、Farasan Banks 的中架 (FBM) 和近海 (FBI)，以及 Thuwal (TI) 的近海。从 198 个样本中提取基因组 DNA，然后扩增核糖体 DNA 内部转录间隔区 2 (ITS-2) 和叶绿体质体微环 (psbAncr) 的非编码区。Durusdinium 和 Cladocopium 的六个谱系（Pt-1-a、Pt-1-b、Pt-1-c、Pt-1-d、Pt-3-a、Pt-3-b) 基于两个标记区域的序列进行鉴定。从FBI（高SST，高Chl a）到FBO（低SST，低Chl a）观察到共生科谱系组成的变化。分子方差分析表明，距海岸的距离最有可能预测 Cladocopium 谱系的差异。多项逻辑回归分析显示，随着 SST 的增加，不同 Cladocopium 谱系之间发生了转变。一种 Cladocopium 谱系 Pt-1-b 在高 SST 时表现出较高的流行率，并且其流行率增加的速度与耐热 Durusdinium 相同。此外，Cladocopium 谱系 Pt-3-a 对低 Chl a 浓度具有高亲和力。该研究表明，SST 和 Chl a 浓度的环境变化是个体宿主 P.tuberculosa 菌落内优势共生科多样性的重要预测因子。我们的理论是，共生科不同谱系的灵活性允许通才 P.tuberculosa 生活在红海南部的各种环境中。