The effects of spatial and temporal environmental heterogeneities on persistence in a laboratory experimental community

Among many stabilizing factors for community dynamics, spatial and temporal heterogeneities have been widely considered in recent years as two of the most important properties. However, the difference between the two types of heterogeneities have not been studied, except for Clark and Yoshimura (1993). We evaluated experimentally the effect of temporal and spatial heterogeneities on the persistence of a biological community. The experimental communities consisted of one parasitic wasp species, one bean weevil species, and two kinds of bean. Temporal and spatial heterogeneities of experimental communities were generated by kinds and timing of bean supply. Of all the experimental communities, the most persistent community was a temporally and spatially homogeneous community with Red Kidney bean as primary resource. Compared to spatially heterogeneous communities, temporally heterogeneous communities were more persistent. These results were easily explained by considering the attack rate of parasitic wasps and the difference between arithmetic and geometric means. In order to discuss the relative importance of environmental heterogeneity and the mode of biological interaction on community persistence, we have to measure the degree of environmental heterogeneity as the rate of change of the strength of interspecific interactions.