The macroecology of fish migration

Aim: We still lack a consensus on the main variables driving changes in migratory strategies. Different hypotheses have been proposed: productivity, energy, environmental heterogeneity, and genetic predisposition. This work takes an integrative view and analyzes migrations from a macroecological perspective estimating the extent to which different environmental variables and historic factors influence migratory life histories. Location: Global Time period: Current Major taxa studied: Actinopterygian fishes Methods: Using public domain museum records, global repositories, and global measures of temperature, productivity, precipitation and heterogeneity, we spatially analyzed the distribution of anadromous, catadromous, amphidromous, potamodromous and oceanodromous migratory fish using 1676 species and compared it to 1616 non-migratory fishes. After analyzing the individual roles of productivity and temperature in shaping biodiversity, we conducted path analyses including several environmental variables and principal coordinates of phylogenetic structure (PCPS). Results: The different migratory strategies are not evenly distributed around the globe and phylogeny is a relevant variable in shaping current patterns. Productivity is positively related to species richness, except for anadromy and potamodromy, where we observed a unimodal curve. Temperature significantly drives migratory species richness (except for anadromy). The role of environmental heterogeneity, measured as temperature seasonality and annual range is strongest for anadromous species, which helps explain their skewed distribution towards higher latitudes and why the kinetic-energy hypothesis fails in explaining their richness patterns. Main conclusions: Overall, migratory fish richness can be explained by the interaction of multiple variables, such as productivity, temperature, environmental heterogeneity, and the role of phylogeny, but these variables interact differentially in each strategy, diverging mostly for the anomalous anadromous fishes. Integrating these results into a global framework to better understand the evolutionary and ecological dynamics of migration will help with predicting responses to anthropogenic climate change

研究目的：目前学界尚未就调控洄游策略演变的核心变量达成共识。已有研究先后提出四类调控假说：生产力、能量供给、环境异质性与遗传易感性。本研究采用整合视角，从宏生态学层面展开分析，量化不同环境变量与历史因素对洄游生活史的影响程度。
研究区域：全球范围
研究时段：当前
研究类群：辐鳍鱼纲（Actinopterygian fishes）鱼类

研究方法：本研究整合公开馆藏博物馆记录、全球公共数据库资源，以及温度、生产力、降水与环境异质性的全球量化指标，针对1676种涵盖溯河洄游（anadromous）、降河洄游（catadromous）、双洄游（amphidromous）、淡水洄游（potamodromous）与海洋洄游（oceanodromous）五类洄游策略的鱼类，开展空间分布分析，并与1616种非洄游鱼类进行对比。在明确生产力与温度对生物多样性的单独调控作用后，本研究纳入多环境变量与系统发育结构主坐标分析（principal coordinates of phylogenetic structure, PCPS），构建路径分析（path analyses）模型。

研究结果：不同洄游策略的鱼类在全球的分布并不均匀，系统发育关系是塑造当前分布格局的重要变量。生产力与物种丰富度呈正相关关系，但溯河洄游与淡水洄游类群除外，二者与生产力呈单峰曲线关系。温度显著调控洄游鱼类的物种丰富度（溯河洄游类群除外）。以温度季节变异性与年温度范围表征的环境异质性，对溯河洄游类群的影响最为显著，这一结果解释了为何溯河洄游鱼类多集中分布于高纬度区域，同时也阐明了动能能量假说无法合理解释该类群丰富度格局的原因。

主要结论：总体而言，洄游鱼类的物种丰富度可通过生产力、温度、环境异质性与系统发育等多变量的交互作用进行解释，但这些变量对不同洄游策略的调控效应存在显著差异，其中以异常的溯河洄游类群表现最为突出。将本研究结果整合至全球分析框架中，以深化对洄游行为演化与生态动力学的理解，将有助于预测鱼类类群对人为气候变化的响应。