Traits, landmarks and outlines: Three congruent sides of a tale on coral reef fish morphology

Quantifying the morphology of organisms remains fundamental in ecology given the form-function relationship. Morphology is quantifiable in traits, landmarks, and outlines, and the choice of approach may influence ecological conclusions to an unknown extent. Here, we apply these three approaches to 111 individual coral reef fish of 40 species common in Micronesia. We investigate the major dimensions of morphological variability among individuals, families, and predefined feeding functional groups. We find that although the approaches are complementary, they coincide in capturing elongation as the main dimension of variability. Further, the choice of approach led to different interpretations regarding the degree of morphological differentiation among taxonomic and feeding functional groups. We also use each morphology dataset to compute community-scale morphological diversity on Palauan reefs and investigate how the choice of dataset affects the detection of differences among sites and wave exposure levels. The exact ranking of sites from highest to lowest morphological diversity was sensitive to the approach used, but not the broad spatial pattern of morphological diversity. Conclusions regarding the effect of wave exposure on morphological diversity were robust to the approach used. Biodiversity hotspots (e.g. areas of exceptionally high diversity and/or endemism) are considered important conservation targets but their location may depend on the biodiversity metric used. In the same vein, our results caution against labelling particular sites as morphological diversity hotspots when metrics consider only a single aspect of morphology.鉴于形态与功能的关联，对生物体形态进行量化仍是生态学研究的核心基础。生物体的形态可通过性状、地标点（landmarks）与轮廓（outlines）三种方式量化，而量化方法的选择可能在未知程度上影响生态学结论的可靠性。本研究针对密克罗尼西亚海域常见的40种共111条珊瑚礁鱼类个体，采用上述三种量化方法开展分析，探究了个体间、科间以及预先定义的摄食功能群之间的形态变异主要维度。研究结果表明，尽管三种方法互为补充，但均一致将身体伸长度作为形态变异的首要维度。此外，量化方法的选择会导致对分类群与摄食功能群间形态分化程度的解读出现差异。本研究还利用各形态学数据集，计算了帕劳珊瑚礁的群落尺度形态多样性，并探究了数据集选择如何影响不同采样点与波浪暴露水平间差异的检测结果。按形态多样性从高到低对采样点的精确排序会受所用量化方法的影响，但形态多样性的整体空间格局则不受此影响。关于波浪暴露对形态多样性影响的研究结论，不受所用量化方法的影响，具有较强的稳健性。生物多样性热点地区（即物种多样性或特有性极高的区域）被视为重要的保护目标，但其具体位置可能取决于所采用的生物多样性度量指标。同理，本研究结果警示：若仅采用单一形态维度的度量指标，切勿轻易将特定采样点划定为形态多样性热点地区。