Parasite-Host Population Systems and Genetic Stability

Abstract

Parasite populations (houseflies) were exposed to and isolated with each of six simulated host-plant types with the following six chemicals as toxicants (resistant factors) in the plant types: citric acid, copper sulfate, magnesium nitrate, sodium chloride, ammonium phosphate, and potassium hydroxide. When the fly population was exposed to a single host-toxicant type, the fly evolved rapidly (seven to 10 generations) to overcome the single host toxic ant. However, when the fly population was exposed to all six simulated hogfishes types in one multi cell system, the fly population did not evolve and overcome any of the host-toxic ant types. Relative to the genetic feedback mechanism, coevolution, and stability among parasite and host, the evidence suggests that genetic stability (preventing the parasite from overcoming host resistance) is possible in parasite-host population systems with the appropriate combination of (1) suitable genetic diversity (resistant characters) in the host population, (2) ample gene flow between parasite colonies (if colonies occur in the parasite-host population system), and (3) suitable selection coefficients on the parasite population resulting from its host population