Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967–2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the groundwater. We used the ‘Northern Peel region’, a historically iron-rich peat landscape in The Netherlands as a case study. This allowed us to test the hypothesis that niche segregation in two closely related species of stickleback occurred along a physiological axis. Patterns in stickleback occurrence were strongly associated with spatial patterns in iron concentrations before 1979: iron-rich grid cells were avoided by three-spined stickleback (Gasterosteus aculeatus, Linnaeus 1758) and preferred by nine-spined stickleback (Pungitius pungitius, [Linnaeus, 1758]). After 1979, the separation between both sticklebacks became weaker, corresponding to a decreased influence of local groundwater on stream water quality. The way both species changed their distribution in the field provides a strong indication that they differ in their susceptibility to iron-rich conditions. These observed differences correspond with differences in their respiration physiology, tolerance of poor oxygen conditions and overall life-history strategy documented in the literature. Our results exemplify how species can partition niche along a non-structural niche axis, such as sublethal iron-rich conditions. Other fish species may similarly segregate along concentration gradients in iron, while sublethal concentrations of other metals such as copper may similarly impact fish via respiratory impairment and reduced aerobic scope.

中文翻译：

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生态系统沿生理轴在两个密切相关的棘背鱼种中的生态位隔离：解释由于铁引起的呼吸功能障碍而导致鱼类分布的十年变化。

急性接触铁可能会对鱼类致死，但是铁的长期亚致死影响需要进一步研究。在这里，我们研究了两个紧密相关的棘背类物种的时空分布（1967-2004年）是否与地下水中铁浓度的空间分布相匹配。我们以“北部果皮地区”（Northern Peel region）为例，该地区是荷兰历史上富含铁的泥炭地貌。这使我们能够检验这样的假设，即沿生理轴在两个密切相关的棘背类物种中发生了利基分离。1979年以前，棘背鱼发生的模式与铁浓度的空间模式密切相关：三刺棘背鱼（Gasterosteus aculeatus，Linnaeus 1758），并受到九棘刺棘背preferred（Pungitius pungitius，[Linnaeus，1758年]。1979年之后，两个棘背类动物之间的分离变得更弱，这对应于本地地下水对溪流水质的影响减小。两种物种改变其在田间分布的方式有力地表明，它们对富铁条件的敏感性不同。这些观察到的差异与文献中记载的呼吸生理，对恶劣的氧气条件的耐受性以及整个生命史策略的差异相对应。我们的结果例证了物种如何沿非结构性利基轴（例如，富铁致死条件）分配利基。其他鱼类也可能沿着铁中的浓度梯度分离，