Abstract：
Contemporary symbioses in extreme environments can give an insight into mechanisms that stabilize species interactions during environmental change. The intertidal sea anemone, Anthopleura elegantissima, engages in a nutritional symbiosis with microalgae similar to tropical coral, but withstands more intense environmental fluctuations during tidal inundations. In this study, we compare baseline symbiotic traits and their sensitivity to thermal stress within and among anemone aggregations across the intertidal using a laboratory-based tank experiment to better understand how fixed genotypic and plastic environmental effects contribute to the successful maintenance of this symbiosis in extreme habitats. High intertidal anemones had lower baseline symbiont-to-host cell ratios under control conditions, but their symbionts had higher baseline photosynthetic efficiency compared to low intertidal anemone symbionts. Symbiont communities were identical across all samples, suggesting that shifts in symbiont density and photosynthetic performance could be an acclimatory mechanism to maintain symbiosis in different environments. Despite lower baseline symbiont-to-host cell ratios, high intertidal anemones maintained greater symbiont-to-host cell ratios under heat stress compared with low intertidal anemones, suggesting greater thermal tolerance of high intertidal holobionts. However, the thermal tolerance of clonal anemones acclimatized to different zones was not explained by tidal height alone, indicating additional environmental variables contribute to physiological differences. Host genotype significantly influenced anemone weight, but only explained a minor proportion of variation among symbiotic traits and their response to thermal stress, further implicating environmental history as the primary driver of holobiont tolerance. These results indicate that this symbiosis is highly plastic and may be able to acclimatize to climate change over ecological timescales, defying the convention that symbiotic organisms are more susceptible to environmental stress.
摘要：
极端环境中的当代共生可以深入了解在环境变化过程中稳定物种相互作用的机制。潮间带海葵，红斑秀兰,与类似热带珊瑚的微藻进行营养共生，但在潮汐淹没期间可以承受更强烈的环境波动。在这项研究中,我们使用基于实验室的储罐实验,比较了潮间带海葵聚集内部和之间的基线共生性状及其对热应力的敏感性,以更好地了解固定基因型和塑性环境影响如何有助于在极端生境中成功维持这种共生.在对照条件下，高潮间带海葵具有较低的基线共生体与宿主细胞比率，但与低潮间海葵共生体相比，它们的共生体具有更高的基线光合效率。所有样本的共生体群落都是相同的，表明共生体密度和光合性能的变化可能是在不同环境中维持共生的一种抑制机制。尽管较低的基线共生体与宿主细胞比率，与低潮间海葵相比，高潮间海葵在热应激下保持更大的共生体与宿主细胞比率，表明高潮间带全离子的耐热性更高。然而,适应不同区域的克隆海葵的耐热性不能仅靠潮汐高度来解释，表明额外的环境变量有助于生理差异。宿主基因型显著影响海葵重量，但只解释了共生性状及其对热胁迫的反应之间的一小部分变异，进一步暗示环境历史是整体耐受性的主要驱动因素。这些结果表明，这种共生是高度可塑性的，可能能够适应生态时间尺度上的气候变化，无视共生生物更容易受到环境压力的惯例。
