Relative importance of spatial and temporal scales in a patchy environment

Abstract

The purpose of this study was to examine the relative importance of temporal and spatial scales of habitat heterogeneity on regional abundance of populations in patchy environments. Temporal scale is habitat lifespan relative to the generation time of the organism, and spatial scale is the distance between habitat patches relative to the dispersal distance of the organism. A spatially explicit simulation model of population growth and dispersal was constructed for a population that is distributed on a grid. The grid contains two sorts of habitat, useable and nonuseable habitat; useable habitat occurs in habitat patches. Habitat patches are transient; they are “born” at random with a specified probability, and they exist for a specified length of time, the patch “lifespan.” Distance between patches is directly related to habitat patch size when the fraction of the grid in useable habitat is held constant. A factorial simulation experiment was conducted in which the fraction of the grid in useable habitat was held constant and patch lifespan, patch size, and species dispersal distance were varied. The relative importance of temporal scale (patch lifespan) and spatial scale (patch size, a surrogate for inter-patch distance per species dispersal distance) on regional population size was tested by analysis of variance. Population size increased with increasing temporal scale and decreased with increasing spatial scale. The effect of temporal scale far outweighed the effect of spatial scale. Implications for design of ecological research programmes are discussed.