title: Niche segregation in two closely related species of stickleback along a physiological axis: explaining multidecadal changes in fish distribution from iron-induced respiratory impairment.
abstract: 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.
authors.affiliation: Department of Animal Ecology and Ecophysiology, Institute for Water and Wetland Research, Radboud University, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands ; Bargerveen Foundation, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands ; Marine Biology and Ecology Research Centre, University of Plymouth, Davy Building, Drake Circus, Plymouth, PL4 8AA UK.
authors.forename: Wilco C E P
authors.initials: WC
authors.lastname: Verberk
authors.affiliation: Staatsbosbeheer, Regio Zuid, Spoorlaan 444, 5038 CH Tilburg, The Netherlands.
authors.forename: Piet J J
authors.initials: PJ
authors.lastname: van den Munckhof
authors.affiliation: Experimental Zoology Group, Department of Animal Sciences, Wageningen University, De Elst 1, 6708 WD Wageningen, The Netherlands.
authors.forename: Bart J A
authors.initials: BJ
authors.lastname: Pollux
keywords: Distribution; Heavy metals; Life-history strategy; Oxygen; Physiological tolerance; Toxicity