Howe-Kerr Lauren I, Bachelot Benedicte, Wright Rachel M, Kenkel Carly D, Bay Line K, Correa Adrienne M S
BioSciences at Rice, Rice University, Houston, TX, USA.
Biological Sciences, Smith College, Northampton, MA, USA.
Glob Chang Biol. 2020 Apr;26(4):2220-2234. doi: 10.1111/gcb.14999. Epub 2020 Feb 12.
Coral reefs are declining globally as climate change and local water quality press environmental conditions beyond the physiological tolerances of holobionts-the collective of the host and its microbial symbionts. To assess the relationship between symbiont composition and holobiont stress tolerance, community diversity metrics were quantified for dinoflagellate endosymbionts (Family: Symbiodiniaceae) from eight Acropora millepora genets that thrived under or responded poorly to various stressors. These eight selected genets represent the upper and lower tails of the response distribution of 40 coral genets that were exposed to four stress treatments (and control conditions) in a 10-day experiment. Specifically, four 'best performer' coral genets were analyzed at the end of the experiment because they survived high temperature, high pCO , bacterial exposure, or combined stressors, whereas four 'worst performer' genets were characterized because they experienced substantial mortality under these stressors. At the end of the experiment, seven of eight coral genets mainly hosted Cladocopium symbionts, whereas the eighth genet was dominated by both Cladocopium and Durusdinium symbionts. Symbiodiniaceae alpha and beta diversity were higher in worst performing genets than in best performing genets. Symbiont communities in worst performers also differed more after stress exposure relative to their controls (based on normalized proportional differences in beta diversity), than did best performers. A generalized joint attribute model estimated the influence of host genet and treatment on Symbiodiniaceae community composition and identified strong associations among particular symbionts and host genet performance, as well as weaker associations with treatment. Although dominant symbiont physiology and function contribute to host performance, these findings emphasize the importance of symbiont community diversity and stochasticity as components of host performance. Our findings also suggest that symbiont community diversity metrics may function as indicators of resilience and have potential applications in diverse disciplines from climate change adaptation to agriculture and medicine.
随着气候变化和当地水质使环境条件超出了共生体（宿主及其微生物共生体的集合）的生理耐受范围，全球珊瑚礁正在衰退。为了评估共生体组成与共生体应激耐受性之间的关系，对来自八个鹿角珊瑚（Acropora millepora）基因型的甲藻内共生体（共生藻科）的群落多样性指标进行了量化，这些基因型在各种应激源下生长良好或反应不佳。这八个选定的基因型代表了在为期10天的实验中接受四种应激处理（和对照条件）的40个珊瑚基因型反应分布的上下尾部。具体而言，在实验结束时分析了四个“表现最佳”的珊瑚基因型，因为它们在高温、高pCO₂、细菌暴露或综合应激源下存活下来，而四个“表现最差”的基因型则因其在这些应激源下经历了大量死亡而被表征。在实验结束时，八个珊瑚基因型中的七个主要含有枝管藻属共生体，而第八个基因型则由枝管藻属和耐热藻属共生体共同主导。表现最差的基因型中的共生藻科α和β多样性高于表现最佳的基因型。与对照相比，表现最差的基因型中的共生体群落在应激暴露后的差异也更大（基于β多样性的标准化比例差异），而表现最佳的基因型则不然。一个广义联合属性模型估计了宿主基因型和处理对共生藻科群落组成的影响，并确定了特定共生体与宿主基因型表现之间的强关联，以及与处理之间的较弱关联。尽管优势共生体的生理和功能有助于宿主表现，但这些发现强调了共生体群落多样性和随机性作为宿主表现组成部分的重要性。我们的发现还表明，共生体群落多样性指标可能作为恢复力的指标发挥作用，并在从气候变化适应到农业和医学等不同学科中具有潜在应用。
