Data from: Environmental niche divergence between genetically distant lineages of an endangered water beetle

Historically, there has been considerable disagreement between researchers about the criteria used to discriminate among species. Decisions based on traditional morphological and genetic data alone can be potentially problematic, especially if the hypotheses are contradictory. Today, taxonomy is integrating new methods from different disciplines that study species’ limits and evolution; this diverse range of evidence aids researchers in the recognition of species. Differences in niche characteristics could become a new and useful criterion in helping to decide the status of conflicting taxonomical entities. Ochthebius glaber (family Hydraenidae) is an endangered water beetle typical from southeast Iberian hypersaline streams that shows three clear discrete genetic units within its distribution range. However, there is no evidence to date that these lineages of O. glaber exhibit any adaptive morphological or ecological divergence. Using a modelling approach directed to generate niche representation from distributional data, we found a significant environmental niche divergence for allopatric lineages of O. glaber that followed an aridity gradient. Although we can not conclude firmly at present that the separate populations of O. glaber studied represent separate, reproductively isolated species, this study complements and supports previous phylogeographic analyses through the inclusion of measures of another form of evolutionary change; in this case, ecological diversification. Despite the existence of some methodological limitations, also discussed in this work, we emphasise the importance of recent conceptual advances that allow taxonomy to improve species delimitation practices through the integration of theory and methods from disciplines that study the origin and evolution of species.长期以来，分类学研究者在物种鉴别标准上始终存在显著分歧。仅依托传统形态学与遗传数据做出的分类判定，可能存在潜在风险，尤其当相关假说彼此矛盾时。当前，分类学（taxonomy）正积极融合多学科新兴方法，这些学科聚焦物种边界与演化机制研究；多元证据体系为研究者的物种识别工作提供了有力支撑。生态位特征（niche characteristics）差异有望成为一项全新的实用判定标准，助力解决存在争议的分类单元（taxonomical entities）的分类地位争议。光滑细泥甲（Ochthebius glaber，隶属于水龟虫科（Hydraenidae））是伊比利亚半岛东南部高盐溪流特有的濒危水生甲虫，其分布范围内已被证实存在三个清晰的离散遗传单元（genetic units）。但截至目前，尚无研究证据表明该物种的这些支系存在适应性形态或生态分化。本研究采用基于分布数据构建生态位表征的建模方法（modelling approach），结果显示该物种的异域支系（allopatric lineages）沿干旱梯度（aridity gradient）存在显著的环境生态位分化（environmental niche divergence）。尽管目前尚无法确凿认定本研究所涉及的O. glaber分离种群属于独立的、生殖隔离物种（reproductively isolated species），但本研究纳入了另一维度的进化变化测度——即生态多样化（ecological diversification），从而补充并佐证了此前的系统地理学分析（phylogeographic analyses）结果。尽管本研究存在部分方法学局限（methodological limitations），本文亦对其进行了讨论，但我们仍强调近期分类学概念进展的重要价值：这些进展允许分类学通过整合研究物种起源与演化的多学科理论与方法，进一步优化物种界定（species delimitation）实践。