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Summary: 1
CHAOS FROM LINEAR FREQUENCYDEPENDENT SELECTION
LEE ALTENBERG
Department of Zoology, Duke University, Durham, NC 27706
Submitted February 13, 1989; Revised March 9, 1990; Accepted May 20, 1990 1
Abstract.---The simplest diploid model of frequencydependent selection can gen
erate periodic and chaotic trajectories for the allele frequency. The model is of
a randomly mating, infinite diploid population with nonoverlapping generations,
segregating for two alleles under frequencydependent viability selection. The
fitnesses of each of the three genotypes is a linear function of the frequencies of
the three genotypes. The region in the space of the coefficients that yields cy
cles and chaos is explored analytically and numerically. The model follows the
perioddoubling route to chaos as seen with logistic growth models, but includes
additional phenomena such as the simultaneous stability of cycling and chaos. The
general condition for cycling or chaos is that the heterozygote deleteriously effect
all genotypes. The kinds of ecological interactions that could give rise to these fit
ness regimes producing cycling and chaos include cannibalism, predator attraction,
habitat degradation, and disease transmission.
The possibilities for complex dynamical behavior from even the simplest models
of population growth regulation (May, 1974, 1976) have led to the examination of
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