Variable performance of individuals: the role of population density and endogenously formed landscape heterogeneity

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Abstract
Summary: Individuals can show positive correlations in performance (e.g. growth and reproduction) through time beyond the effects of size or age. This ‘performance autocorrelation’ has been attributed previously to traits that differ among individuals or to extrinsic generators of environmental heterogeneity. A model of mobile consumers on a dynamic resource showed that consumer foraging gave rise to resource heterogeneity that in turn generated autocorrelation in growth in consumers. Resource heterogeneity and growth autocorrelation were most pronounced when consumers were poorer foragers, moving locally and with an imperfect ability to identify the highest resource cells. The model predicted that lowered population density enhanced resource heterogeneity and the strength of growth autocorrelation. Consistent with model predictions, an experiment with tidepool limpets demonstrated that autocorrelation in growth changed with population density, with individuals in lower density tidepools showing stronger temporal correlations in growth. Our model and empirical results contrast with those of previous studies with plants, where dominance and suppression increases with increasing density. Our results suggest that growth autocorrelation can occur without invoking size‐dependent advantages, intrinsic trait differences or extrinsic generators of environmental heterogeneity.