American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Metabolic rate interacts with resource availability to determine individual variation in microhabitat use in the wild”

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Sonya K. Auer, Ronald D. Bassar, Daniel Turek, Graeme J. Anderson, Simon McKelvey, John D. Armstrong, Keith H. Nislow, Helen K. Downie, Thomas A. J. Morgan, Darryl McLennan, and Neil B. Metcalfe (Aug 2020)

Metabolic rate interacts with resource availability to determine individual variation in microhabitat use in the wild

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Atlantic salmon habitat in the Scottish Highlands.<br />(Credit: Sonya K. Auer)
Atlantic salmon habitat in the Scottish Highlands.
(Credit: Sonya K. Auer)

Abstract

Ecological pressures such as competition can lead individuals within a population to partition resources or habitats, but the underlying intrinsic mechanisms that determine an individual’s resource use are not well understood. Here we show that an individual’s own energy demand and associated competitive ability influence its resource use, but only when food is more limiting. We tested whether intraspecific variation in metabolic rate leads to microhabitat partitioning among juvenile Atlantic salmon (Salmo salar) in natural streams subjected to manipulated nutrient levels and subsequent per capita food availability. We found that individual salmon from families with a higher baseline (standard) metabolic rate (which is associated with greater competitive ability) tended to occupy faster flowing water, but only in streams with lower per capita food availability. Faster flowing microhabitats yield more food, but high metabolic rate fish only benefited from faster growth in streams with high food levels, presumably because in low food environments the cost of a high metabolism offset the benefits of acquiring a productive microhabitat. The benefits of a given metabolic rate were thus context-dependent. These results demonstrate that intraspecific variation in metabolic rate can interact with resource availability to determine the spatial structuring of wild populations.