High physiological function for corals with thermally tolerant, host-adapted symbionts

The flexibility to associate with more than one symbiont may considerably expand a host's niche breadth. Coral animals and dinoflagellate micro-algae represent one of the most functionally integrated and widespread mutualisms between two eukaryotic partners. Symbiont identity greatly affects a coral's ability to cope with extremes in temperature and light. Over its broad distribution across the Eastern Pacific, the ecologically dominant branching coral, Pocillopora grandis, depends on mutualisms with the dinoflagellates Durusdinium glynnii and Cladocopium latusorum. Measurements of skeletal growth, calcification rates, total mass increase, calyx dimensions, reproductive output and response to thermal stress were used to assess the functional performance of these partner combinations. The results show both host–symbiont combinations displayed similar phenotypes; however, significant functional differences emerged when exposed to increased temperatures. Negligible physiological difference..., ,能够与多种共生体（symbiont）结合的灵活性，可大幅拓展宿主的生态位宽度（niche breadth）。珊瑚动物与甲藻微藻（dinoflagellate micro-algae）是真核生物间功能整合程度最高、分布最广泛的互利共生关系之一。共生体的种类极大地影响着珊瑚应对极端温度与光照的能力。在东太平洋广泛分布的生态优势分枝型珊瑚——巨枝鹿角珊瑚（Pocillopora grandis），依赖与杜氏甲藻（Durusdinium glynnii）和枝孢甲藻（Cladocopium latusorum）的互利共生。本研究通过测定骨骼生长速率、钙化率、总质量增量、萼部尺寸、繁殖产出以及对热胁迫（thermal stress）的响应，评估了这两组宿主-共生体组合的功能表现。结果显示，两种宿主-共生体组合均呈现出相似的表型（phenotype）；但当暴露于升温环境时，二者便显现出显著的功能差异，而常温下二者的生理差异可忽略……