Spatial scales of population synchrony in predator-prey systems

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Javier Jarillo, Research Unit of Environmental and Evolutionary Biology, Namur Institute of Complex Systems, and Institute of Life, Earth, and the Environment, University of Namur, Namur, Belgium, Bernt-Erik Sæther, Centre for biodiversity dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway, Steinar Engen, Centre for biodiversity dynamics, Department of Mathematical Sciences, Norwegian University of Science and Technology, Trondheim, Norway and Francisco J. Cao-García, IMDEA Nanoscience, Madrid, Spain; Universidad Complutense de Madrid, Madrid, Spain

Background/Question/Methods
Many species show synchronous fluctuations in population size over large geographical areas, which are likely to increase their regional extinction risk. Theoretical analyses of single‐species models have revealed that the degree of population synchrony increases with increasing spatial covariation in environmental fluctuations and increased interchange of individuals, but decreases with local strength of density dependence. More recent studies have further shown how interspecific competition is able to modify the spatial pattern of population synchrony of the species. Here we examine how the spatial synchrony in population dynamics is affected by trophic interactions using a two-species predator-prey model with spatially correlated environmental noise.

Results/Conclusions
In bottom-up regulated systems, the predator has a larger spatial scale of population synchrony than the prey. This result might indicate that in food webs, the spatial scale of synchrony of the predator populations increases beyond the scale of the spatial autocorrelation in the environmental noise and in the prey fluctuations. Harvesting the prey increases the spatial scale of population synchrony of the predator, while harvesting the predator reduces the spatial scale of the population fluctuations of its prey. Hence, the development of sustainable harvesting strategies should also consider the impact of harvesting or human perturbations on other trophic levels, as they can affect food web structures over large geographical areas.