A simple spatially explicit ideal-free distribution: a model and an experiment

This investigation presents a simple spatially explicit analysis of the ide al-free distribution. The traditional ideal-free distribution assumes discr ete sites with definite boundaries, and predicts how many individuals shoul d occupy each site. In contrast, the present analysis assumes that a forage r's gains gradually decline with distance from a site, and asks where in sp ace individuals ought to be. Although many interesting situations may arise , the analysis asks how individuals should position themselves as the dista nce between two identical sources increases. Nash equilibrium positions sho uld follow a pitchfork pattern as the distance between sites is increased; that is, an individual should maintain a position between two sources when they are close together but should move nearer one of the sources when they are far apart. In addition, the text describes an experimental study that parallels the theoretical analysis. The experiment supports the predicted p itchfork pattern, and provides somewhat weaker support for the predicted di fferences in "individual" and "paired" pitchforks.