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1 July 2008 Determinants of the Strength of Disruptive and/or Divergent Selection Arising from Resource Competition
Peter A. Abrams, Claus Rueffler, Gary Kim
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We investigate how the intensity of competition for resources affects the strength of disruptive selection on a resource acquisition trait. This is done by analyzing several consumer–resource models in which consumers use a linear array of resources. We show that disruptive selection can be diminished under both strong and weak competition, making disruptive selection a unimodal function of the strength of competition. Weak selection under strong competition arises when competition causes the extinction (for self-reproducing resources) or depletion (for abiotic resources) of the most rapidly caught resources. Weak selection under weak competition is a consequence of minimal effects of consumers on resources. The precise relationship between intensity of competition and strength of disruptive selection is sensitive to the shape of the consumer's resource utilization curve and the nature of resource growth. The most strongly unimodal competition–selection relationships result from utilization curves with long tails. Our results show that a simple comparison of the width of the resource abundance distribution and the consumer's utilization function is not sufficient to determine whether selection is disruptive. The results may explain some contradictory experimental findings regarding the effect of consumer mortality on the strength of disruptive selection.

Peter A. Abrams, Claus Rueffler, and Gary Kim "Determinants of the Strength of Disruptive and/or Divergent Selection Arising from Resource Competition," Evolution 62(7), 1571-1586, (1 July 2008).
Received: 18 October 2007; Accepted: 1 March 2008; Published: 1 July 2008

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apparent competition
competition coefficient
disruptive selection
frequency-dependent selection
resource competition
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