Ecology. 2014 Apr;95(4):1000-9. doi: 10.1890/13-1445.1.
Abiotic filtering is a major driver of gradients in the structure and functioning of ecosystems from the tropics to the poles. It is thus likely that environmental filtering is an important assembly process at the transition of biogeographical zones where many species occur at their range limits. Shifts in species abundances and association patterns along environmental gradients can be indicative of environmental filtering, which is predicted to be stronger in areas of high abiotic stress and to promote increased similarity of ecological characteristics among co-occurring species. Here we test these hypotheses for scleractinian corals along a broad latitudinal gradient in high-latitude eastern Australia, where corals occur at the margins of their ranges and environmental tolerances. We quantify variation in taxonomic, zoogeographic, and functional patterns combined with null model approaches and demonstrate systematic spatial variation in community structure and significant covariance of species abundance distributions and functional characteristics along the latitudinal gradient. We describe a strong biogeographic transition zone, consistent with patterns expected under abiotic filtering, whereby species are sorted along the latitudinal gradient according to their tolerances for marginal reef conditions. High-latitude coastal reefs are typified by widely distributed, generalist, stress-tolerant coral species with massive and horizontally spreading morphologies and by diminishing influence of tropical taxa at higher latitudes and closer to the mainland. Higher degree of ecological similarity among co-occurring species than expected by chance supports the environmental filtering hypothesis. Among individual traits, the structural traits corallite size and colony morphology were filtered most strongly, suggesting that characteristics linked to energy acquisition and physical stability may be particularly important for coral survival in high-latitude environments. These findings highlight interspecific differences and species interactions with the environment as key drivers of community organization in biogeographic transition zones and support the hypothesis that environmental filters play a stronger role than biotic interactions in structuring ecological communities in areas of high abiotic stress.
非生物过滤是从热带到极地的生态系统结构和功能梯度的主要驱动因素。因此，环境过滤很可能是生物地理区过渡带物种丰富度和关联模式的重要组装过程，在这些过渡带，许多物种都处于其分布范围的极限。物种丰度和沿环境梯度的关联模式的变化可以指示环境过滤，环境过滤预计在生物胁迫较大的地区更强，并促进共存物种的生态特征相似性增加。在这里，我们沿着澳大利亚高纬度东部的一个广泛的纬度梯度测试了这些关于硬珊瑚的假设，在那里珊瑚处于其分布范围和环境容忍度的边缘。我们定量了分类学、动物地理学和功能模式的变化，结合了零模型方法，并沿着纬度梯度证明了群落结构的系统空间变化和物种丰度分布和功能特征的显著协方差。我们描述了一个强烈的生物地理过渡带，与预期的非生物过滤模式一致，即根据其对边缘珊瑚礁条件的耐受性，物种沿着纬度梯度进行分类。高纬度沿海珊瑚礁的特点是分布广泛、普遍存在、耐受压力的珊瑚物种，具有块状和水平扩展的形态，并且在较高纬度和更接近大陆的地方，热带分类群的影响逐渐减弱。共存物种之间比随机预期更高的生态相似性支持环境过滤假设。在个体特征中，珊瑚虫大小和珊瑚虫形态等结构特征被过滤得最强，这表明与能量获取和物理稳定性相关的特征可能对珊瑚在高纬度环境中的生存特别重要。这些发现强调了种间差异和物种与环境的相互作用是生物地理过渡带群落组织的关键驱动因素，并支持了这样的假设，即在生物胁迫较大的地区，环境过滤比生物相互作用在构建生态群落方面发挥更强的作用。
