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Dispersal from an old to a new resource involves two components: (1) the number of dispersants, and (2) behavioral adaptations determining the probability of discovering a new resource. Dispersant numbers may be increased by dispersing at a younger stage, decreasing the biomass of individuals developed prior to dispersal and/or reducing the biomass of males. The probability of founding a new colony can be maximized if females mate before dispersal and/or through phoresy on a reliable host. The utility of the analysis is illustrated in comparisons of dispersal by three mites. Tetranychid mites maximize the number of dispersants but have a very low probability of dispersal. Poecilochirus is reliably dispersed by its host and has no adaptations to increase dispersant numbers. Iponemus feeds on scolytid eggs and is also phoretic on scolytids, thus, its probability of dispersal is maximal, but there is a direct selective disadvantage if resources are wasted so the size and frequency of males and females is modified to maximize the yield of dispersants from a scolytid egg.
The American Naturalist © 1970 The University of Chicago Press