Comparative Dynamics of a Single-Host Aphid. II. Theoretical Consequences

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Abstract
A simulation model, developed for one population, can reproduce the dynamics of other populations of the species, given appropriate values of external parameters. A field test of the model is described [for a population of Masonaphis maxima]. Fecundity, generation time and morph proportions jointly optimize both the initial population increase and the subsequent, relatively constant, population density. Six environmental factors ultimately determine these population parameters. Several ecological mechanisms, including territoriality and the nuclear family, restrict individual fecundity to the level which is optimal for the population. An ecological argument negates the .times. 2 advantage of parthenogenesis to individual mothers, except when the whole population is rapidly expanding. Possible ecological advantages of sex are examined.