Looks Can Be Deceiving: Morphological Traits Are Weakly Associated With the Isotopic Niches of Freshwater Fishes

IF 6 1区环境科学与生态学 Q1 ECOLOGY

Global Ecology and Biogeography Pub Date : 2025-09-16 DOI:10.1111/geb.70124

Julian D. Olden, Friedrich W. Keppeler, Timothy D. Jardine, Stéphanie Boulêtreau, Chris Harrod, Michelle C. Jackson, Angus R. McIntosh, Marie-Elodie Perga, Josie South, Pablo Tedesco, Chloé Vagnon, Julien Cucherousset

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引用次数: 0

Abstract

Aim

Fueled by the emergence of global-scale databases, fish morphological traits are now routinely used as a proxy for trophic ecology when estimating functional diversity. Yet, a rigorous empirical validation of trophic-morphology relationships is lacking. This study offers a global test of whether species' morphology is associated with a known indicator of trophic ecology, stable isotope ratios of carbon and nitrogen.

Location

Worldwide.

Time Period

1992–2023.

Major Taxa Studied

Freshwater fishes (Actinopterygii).

Methods

Isotope-morphology relationships were examined using δ¹³C and δ¹⁵N values from 811 fish communities and ten species-level morphological traits with direct relevance for foraging behaviour (body length, body shape, and position of the mouth, eyes and fins) for 1282 species. Associations were assessed with Multiple Regression on Distance Matrices and Multivariate Generalised Linear Models (MGLM). Analyses were repeated at the individual level for five fish species.

Results

Species morphological similarities explained, on average, 10% of the variation in stable isotope values for fish communities, with > 6% of the communities exhibiting statistically significant associations. The MGLM explained 53% of the variation in δ¹³C and 48% in δ¹⁵N, with approximately 97% and 77% of this variation, respectively, attributed to the site identity (random effect), not the morphological traits. Individual traits contributed minimally (each < 1% variation explained), except for oral gape length (8.3%) and maximum body length (4.7%). Herbivores had significantly weaker isotope-morphology correlations than omnivores and carnivores for δ¹⁵N, while no significant differences were observed for δ¹³C. At the individual level, morphology explained 0% to 16% of isotopic variation within populations, averaging 4%.

Main Conclusions

Weak isotope-morphology relationships for freshwater fishes may arise from the influence of a host of biological, environmental, or methodological factors, or may truly indicate a fundamental disconnection between morphological traits measured at the species level and the trophic niche of populations that are manifested in food webs. Ecologists should recognise the limitations of assuming morphological traits are ‘functional’ in the sense that they can offer a reasonable proxy of a species' trophic ecology at large scales.

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外表可能具有欺骗性：淡水鱼的形态特征与同位素生态位的关系很弱

在全球规模数据库的推动下，鱼类形态特征现在通常被用作估计功能多样性时营养生态学的代理。然而，缺乏对营养形态关系的严格经验验证。该研究提供了一个全球性的测试，以确定物种形态是否与已知的营养生态指标——碳和氮的稳定同位素比率有关。淡水鱼类（放线鱼科）的主要分类群。方法利用811个鱼类群落的δ13C和δ15N值，以及与1282种鱼类的觅食行为（体长、体型、口、眼和鳍的位置）直接相关的10个物种水平的形态特征，对同位素形态关系进行了研究。用距离矩阵多元回归和多元广义线性模型（MGLM）评估相关性。在个体水平上对五种鱼类进行了重复分析。结果物种形态相似性平均解释了鱼类群落稳定同位素值变化的10%，其中6%的群落表现出统计学上显著的相关性。MGLM解释了53%的δ13C和48%的δ15N变异，其中约97%和77%的变异分别归因于位点身份（随机效应），而不是形态特征。除了口口长度（8.3%）和最大体长（4.7%）外，个体性状的贡献最小（每1%的变异被解释）。草食动物δ15N的同位素形态相关性显著弱于杂食动物和食肉动物，而δ13C的同位素形态相关性无显著差异。在个体水平上，形态解释了种群内0%至16%的同位素变化，平均为4%。淡水鱼的弱同位素-形态关系可能受到一系列生物、环境或方法学因素的影响，或者可能真正表明在物种水平上测量的形态特征与食物网中表现出来的种群营养生态位之间存在根本脱节。生态学家应该认识到假设形态特征是“功能性的”的局限性，因为它们可以在大尺度上提供一个物种营养生态的合理代理。

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来源期刊

Global Ecology and Biogeography 环境科学-生态学

CiteScore

12.10

自引率

3.10%

发文量

170

审稿时长

3 months

期刊介绍： Global Ecology and Biogeography (GEB) welcomes papers that investigate broad-scale (in space, time and/or taxonomy), general patterns in the organization of ecological systems and assemblages, and the processes that underlie them. In particular, GEB welcomes studies that use macroecological methods, comparative analyses, meta-analyses, reviews, spatial analyses and modelling to arrive at general, conceptual conclusions. Studies in GEB need not be global in spatial extent, but the conclusions and implications of the study must be relevant to ecologists and biogeographers globally, rather than being limited to local areas, or specific taxa. Similarly, GEB is not limited to spatial studies; we are equally interested in the general patterns of nature through time, among taxa (e.g., body sizes, dispersal abilities), through the course of evolution, etc. Further, GEB welcomes papers that investigate general impacts of human activities on ecological systems in accordance with the above criteria.