Habitat selection and the ideal free distribution: Pemphigus aphids revisited

Background/Question/Methods The spatial distribution of a population of foragers is the result of habitat selection by individuals. However, one of the most fundamental models of forager distribution, the ideal free distribution, predicts the result of habitat selection without explicit reference to an individual forager’s decision-making process. This disconnect between individual behavior and population distribution has motivated a large body of theoretical and empirical work to address the question: How do animals select habitats, and do they  possess the perceptual ability to assess habitat quality? I will re-analyze published data from a model system, Pemphigus aphids, in which the fitness consequences of habitat selection can be quantified.

Results/Conclusions Previous research on this system has resulted in two conflicting interpretations of the population-level distribution patterns: 1) an ideal free distribution arises from individual habitat assessment and adaptive decision-making, or 2) the observed distribution is merely a consequence of temporal variation in habitat availability. I will show that neither of these simple behavioral models (select the best patch vs. settle in any available patch) suffices to explain the observed population distribution. Instead, I will argue that the empirical pattern suggests that a more complex habitat selection process must occur in Pemphigus aphids.