Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA.
Proc Biol Sci. 2012 Jul 7;279(1738):2609-18. doi: 10.1098/rspb.2012.0055. Epub 2012 Feb 24.
Some reef-building corals have been shown to respond to environmental change by shifting the composition of their algal symbiont (genus Symbiodinium) communities. These shifts have been proposed as a potential mechanism by which corals might survive climate stressors, such as increased temperatures. Conventional molecular methods suggest this adaptive capacity may not be widespread because few (∼25%) coral species have been found to associate with multiple Symbiodinium clades. However, these methods can fail to detect low abundance symbionts (typically less than 10-20% of the total algal symbiont community). To determine whether additional Symbiodinium clades are present, but are not detected using conventional techniques, we applied a high-resolution, real-time PCR assay to survey Symbiodinium (in clades A-D) from 39 species of phylogenetically and geographically diverse scleractinian corals. This survey included 26 coral species thought to be restricted to hosting a single Symbiodinium clade ('symbiotic specialists'). We detected at least two Symbiodinium clades (C and D) in at least one sample of all 39 coral species tested; all four Symbiodinium clades were detected in over half (54%) of the 26 symbiotic specialist coral species. Furthermore, on average, 68 per cent of all sampled colonies within a given coral species hosted two or more symbiont clades. We conclude that the ability to associate with multiple symbiont clades is common in scleractinian (stony) corals, and that, in coral-algal symbiosis, 'specificity' and 'flexibility' are relative terms: specificity is rarely absolute. The potential for reef corals to adapt or acclimatize to environmental change via symbiont community shifts may therefore be more phylogenetically widespread than has previously been assumed.
一些造礁珊瑚已被证明可以通过改变其共生藻（属 Symbiodinium）群落的组成来应对环境变化。这些变化被认为是珊瑚应对气候胁迫（如温度升高）的一种潜在机制。传统的分子方法表明，这种适应能力可能并不广泛，因为只有少数（约 25%）珊瑚物种被发现与多种 Symbiodinium 类群相关联。然而，这些方法可能无法检测到低丰度的共生体（通常低于总藻类共生体群落的 10-20%）。为了确定是否存在其他 Symbiodinium 类群，但使用传统技术无法检测到，我们应用了高分辨率实时 PCR 检测方法，对来自 39 种系统发育和地理分布广泛的硬珊瑚物种的 Symbiodinium（在 A-D 类群中）进行了调查。该调查包括 26 种被认为仅局限于单一 Symbiodinium 类群的珊瑚物种（“共生专家”）。我们在所有 39 种受测珊瑚物种的至少一个样本中至少检测到了两个 Symbiodinium 类群（C 和 D）；在超过一半（54%）的 26 种共生专家珊瑚物种中，均检测到了所有四个 Symbiodinium 类群。此外，在给定珊瑚物种的所有采样群体中，平均有 68%的群体同时存在两个或更多共生类群。我们得出的结论是，与多个共生类群相关联的能力在石珊瑚中很常见，并且在珊瑚-藻类共生关系中，“特异性”和“灵活性”是相对的术语：特异性很少是绝对的。珊瑚通过共生体群落变化来适应或适应环境变化的潜力可能比以前假设的更为广泛。
