Department of Biology, The Pennsylvania State University, University Park, PA, USA.
School of Marine Science and Policy, University of Delaware, Lewes, DE, USA.
Proc Biol Sci. 2023 Jul 26;290(2003):20231021. doi: 10.1098/rspb.2023.1021. Epub 2023 Jul 19.
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, , depends on mutualisms with the dinoflagellates and . 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 differences in colonies hosting the more thermally tolerant refute the prevailing view that these mutualisms have considerable growth tradeoffs. Well beyond the Eastern Pacific, pocilloporid colonies with are found across the Pacific in warm, environmentally variable, near shore lagoonal habitats. While rising ocean temperatures threaten the persistence of contemporary coral reefs, lessons from the Eastern Pacific indicate that co-evolved thermally tolerant host-symbiont combinations are likely to expand ecologically and spread geographically to dominate reef ecosystems in the future.
与多个共生体建立联系的灵活性可以极大地扩展宿主的生态位宽度。珊瑚动物和甲藻微藻代表了两种真核生物伙伴之间功能最整合和最广泛的共生关系之一。共生体的身份极大地影响了珊瑚应对温度和光照极端变化的能力。在东太平洋广泛分布的生态优势分枝珊瑚 ， 依赖于与甲藻 和 共生。通过测量骨骼生长、钙化率、总质量增加、萼片尺寸、生殖输出和对热应激的反应，来评估这些共生组合的功能表现。结果表明，这两种宿主-共生体组合表现出相似的表型；然而，当暴露在高温下时，就会出现显著的功能差异。在宿主中含有更耐热的共生体的共生体中，生理差异可以忽略不计，这反驳了共生关系存在巨大生长权衡的观点。远在东太平洋之外，太平洋温暖、环境多变的近岸泻湖生境中也存在着带有 的石珊瑚属群体。虽然海洋温度的升高威胁着当代珊瑚礁的生存，但来自东太平洋的经验表明，与共生体共同进化的耐热宿主-共生体组合可能会在生态上扩大，并在未来在地理上传播，以主导珊瑚礁生态系统。
