DYNAMICS OF THE EMERGENCE OF GENETIC-RESISTANCE TO BIOCIDES AMONG ASEXUAL AND SEXUAL ORGANISMS

A stochastic, agent based, evolutionary algorithm, modeling mating, re production, genetic variation, phenotypic expression and selection was used to study the dynamic interactions affecting a multiple-gene syst em. The results suggest that strong irreversible constraints affect th e evolution of resistance to biocides. Resistant genes evolve differen tly in asexual organisms compared with sexual ones in response to vari ous patterns of biocide applications. Asexual populations (viruses and bacteria) are less likely to develop genetic resistance in response t o multiple pesticides or if pesticides are used at low doses, whereas sexual populations (insects for example) are more likely to become res istant to pesticides if susceptibility to the pesticide relates to mat e selection. The adaptation of genes not related to the emergence of r esistance will affect the dynamics of the evolution of resistance. Inc reasing the number of pesticides reduces the probability of developing resistance to any of them in asexual organisms but much less so in se xual organisms. Sequential applications of toxins, were slightly less efficient in slowing emergence of resistance compared with simultaneou s application of a mix in both sexual and asexual organisms. Targeting only one sex of the pest speeds the development of resistance. The fi ndings are consistent to most of the published analytical models but a re closer to known experimental results, showing that nonlinear, agent based simulation models are more powerful in explaining complex proce sses. (C) 1997 Academic Press Limited.