Journal Article

Dimensionality of consumer search space drives trophic interaction strengths

Van M. Savage, Dell, Anthony I., Pawar, Samraat

2012

Overview

Trophic interactions govern biomass fluxes in ecosystems, and stability in food webs. Knowledge of how trophic interaction strengths are affected by differences among habitats is crucial for understanding variation in ecological systems. Here we show how substantial variation in consumption-rate data, and hence trophic interaction strengths, arises because consumers tend to encounter resources more frequently in three dimensions (3D) (for example, arboreal and pelagic zones) than two dimensions (2D) (for example, terrestrial and benthic zones). By combining new theory with extensive data (376 species, with body masses ranging from 5.24 × 10 −14 kg to 800 kg), we find that consumption rates scale sublinearly with consumer body mass (exponent of approximately 0.85) for 2D interactions, but superlinearly (exponent of approximately 1.06) for 3D interactions. These results contradict the currently widespread assumption of a single exponent (of approximately 0.75) in consumer–resource and food-web research. Further analysis of 2,929 consumer–resource interactions shows that dimensionality of consumer search space is probably a major driver of species coexistence, and the stability and abundance of populations. Consumption rates vary substantially between consumers searching in three dimensions (for example, arboreal and pelagic zones), with consumption rates scaling superlinearly with consumer body mass, and those searching in two dimensions (for example, terrestrial and benthic zones), with consumption rates scaling sublinearly with consumer body mass. An added dimension to nutrition Interactions between the feeding habits of different organisms in a food chain or web — trophic interactions — can take place in two or three dimensions, and many communities show a mix of the two. By relating search rate and consumption rate to body mass, the authors show that the relationship between trophic-interaction strength and body size scales sublinearly in two-dimensional interactions but superlinearly in three-dimensional ones. They develop a model to show how this explains differences between, for example, aquatic and terrestrial ecosystems because the extra dimension provides an additional niche or opportunity in which to find resources. As an example, the model predicts that a foraging Galápagos sea lion could enjoy a consumption rate up to 30 times higher in a pelagic zone near the surface of the ocean (in three dimensions) than deep-down in a benthic zone (in two dimensions).

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/601/18 / 704/158/853/2006 / Animal and plant ecology / Animal, plant and microbial ecology / Animals / Biological and medical sciences / Biomass / Biomechanics / Birds - physiology / Body Size / Body Weight / Confidence intervals / Eating - physiology / Ecology / Economic models / Ecosystem / Energy Metabolism / Exponents / Feeding Behavior - physiology / Fishes - physiology / Flight, Animal / Food / Food Chain / Food webs / Foraging behavior / Fundamental and applied biological sciences. Psychology / General aspects / Habitats / Humanities and Social Sciences / Locomotion - physiology / Models, Biological / multidisciplinary / Population Dynamics / Predatory Behavior - physiology / Reproduction - physiology / Ruminants - physiology / Science / Science (multidisciplinary) / Searching / Stability / Strength / Studies / Synecology / Three dimensional / Trophic relationships / Two dimensional