title: Density-independent population projection trajectories of chromosome-substituted lines resistant and susceptible to organophosphate insecticides in Drosophila melanogaster.
abstract: BACKGROUND
  Seasonal fluctuations in susceptibility to organophosphate insecticides were observed in the Katsunuma population of Drosophila melanogaster for two consecutive years; susceptibility to three organophosphates tended to increase in the fall. To examine the hypothesis that variation in fitness among resistant and susceptible genotypes could trigger the change of genetic constitution within the fall population, we investigated density-independent population projection trajectories starting from single adult females with characteristics of chromosome-substituted lines resistant and susceptible to the three organophosphates.
  
  
  RESULTS
  Density-independent population projection trajectories, expressed as the ratios of the number of each chromosome-substituted line to that of line SSS, for which all chromosomes were derived from the susceptible line, showed significant declines in numbers with time for all the resistant chromosome-substituted lines.
  
  
  CONCLUSIONS
  The declining tendency in the density-independent population projection trajectories of the resistant chromosome-substituted lines could explain the simultaneous decline in the levels of resistance to the three organophosphates, observed in the Katsunuma population in the fall.
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK. tmiyo1@staffmail.ed.ac.uk
authors.forename: Takahiro
authors.initials: T
authors.lastname: Miyo
authors.forename: Brian
authors.initials: B
authors.lastname: Charlesworth
mesh_terms: D000367:Age Factors; D000818:Animals; D002875:Chromosomes / Q000235:genetics*; D004331:Drosophila melanogaster / Q000187:drug effects* / Q000235:genetics*; D005260:Female; D014644:Genetic Variation / Q000235:genetics; D005828:Genetics, Population; D005838:Genotype; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides; D008957:Models, Genetic; D010755:Organophosphates / Q000378:metabolism*; D012621:Seasons; D014960:X Chromosome / Q000235:genetics
chemical_list: D007306:Insecticides; D010755:Organophosphates