A test of the cross-scale resilience model: Functional richness in Mediterranean-climate ecosystems

Authors

Donald A. Wardwell, University of Nebraska-Lincoln
Craig R. Allen, University of Nebraska-LincolnFollow
Garry D. Peterson, McGill University, Montreal, Quebec, CanadaFollow
Andrew J. Tyre, University of Nebraska-LincolnFollow

Date of this Version

2007

Comments

Published in Ecological Complexity, Volume 5, Issue 2, June 2008, Pages 165-182

Abstract

Ecological resilience has been proposed to be generated, in part, in the discontinuous structure of complex systems. Environmental discontinuities are reflected in discontinuous, aggregated animal body mass distributions. Diversity of functional groups within body mass aggregations (scales) and redundancy of functional groups across body mass aggregations (scales) has been proposed to increase resilience. We evaluate that proposition by analyzing mammalian and avian communities of Mediterranean-climate ecosystems. We first determined that body mass distributions for each animal community were discontinuous. We then calculated the variance in richness of function across aggregations in each community, and compared observed values with distributions created by 1000 simulations using a null of random distribution of function, with the same n, number of discontinuities and number of functional groups as the observed data. Variance in the richness of functional groups across scales was significantly lower in real communities than in simulations in eight of nine sites. The distribution of function across body mass aggregations in the animal communities we analyzed was non-random, and supports the contentions of the cross-scale resilience model.