Robust assessments of taxonomic and functional diversity are essential components of research programmes aimed at understanding current biodiversity patterns and forecasting trajectories of ecological changes. Yet, evaluating marine biodiversity along its dimensions is challenging and dependent on the power and accuracy of the available data collection methods. Here we combine three traditional survey methodologies (underwater visual census strip transects [UVCt], baited underwater videos [BUV] and small-scale fishery catches [SSFc]), and one novel molecular technique (environmental DNA metabarcoding [eDNA]—12S rRNA and cytochrome oxidase subunit 1 [COI]) to investigate their efficiency and complementarity in assessing fish diversity. We analysed 1,716 multimethod replicates at a basin scale to measure the taxonomic and functional diversity of Mediterranean fish assemblages. Taxonomic identities were investigated at species, genus and family levels. Functional identities were assessed using combinations of morphological, behavioural and trophic traits. We show that: (a) SSFc provided the higher taxonomic diversity estimates followed by eDNA, and then UVCt and BUV; (b) eDNA was the only method able to gather the whole spectrum of considered functional traits, showing the most functionally diversified and least redundant fish assemblages; and (c) the effectiveness of eDNA in describing functional structure reflected its lack of selectivity towards any considered functional trait. Our findings suggest that the reach of eDNA analysis stretches beyond taxon detection efficiency and provides new insights into the potential of metabarcoding in ecological studies.

中文翻译：

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环境 DNA 有效捕获沿海鱼类群落的功能多样性

对分类和功能多样性的稳健评估是旨在了解当前生物多样性模式和预测生态变化轨迹的研究计划的重要组成部分。然而，沿其维度评估海洋生物多样性具有挑战性，并且取决于可用数据收集方法的能力和准确性。在这里，我们结合了三种传统的调查方法（水下视觉普查条带横断面 [UVCt]、诱饵水下视频 [BUV] 和小规模渔业捕捞 [SSFc]）和一种新型分子技术（环境 DNA 元条形码 [eDNA]—12S rRNA 和细胞色素氧化酶亚基 1 [COI]) 以研究它们在评估鱼类多样性方面的效率和互补性。我们分析了 1, 716 种多方法在流域尺度上重复，以测量地中海鱼类组合的分类和功能多样性。在物种、属和科水平上研究了分类学特征。使用形态、行为和营养特征的组合评估功能特性。我们表明：（a）SSFc 提供了更高的分类多样性估计，其次是 eDNA，然后是 UVCt 和 BUV；(b) eDNA 是唯一能够收集所有考虑的功能特征的方法，显示功能最多样化和最少冗余的鱼类组合；(c) eDNA 在描述功能结构方面的有效性反映了它对任何考虑的功能特征缺乏选择性。