Seasonal fluctuation in susceptibility to insecticides within natural populations of Drosophila melanogaster. II. Features of genetic variation in susceptibility to organophosphate insecticides within natural populations of D. melanogaster

Abstract

To elucidate genetic variation in susceptibility to organophosphate insecticides within natural populations of Drosophila melanogaster , we conducted an analysis of variance for mortality data sets of isofemale lines (10-286 lines) used in the previous studies. Susceptibility of isofemale lines to the three organophosphate insecticides was continuously distributed within each natural population, ranging from susceptible to resistant. Analysis of variance showed highly significant variation among isofemale lines in susceptibility to each insecticide for each natural population. Significant genetic variances in susceptibility to the three chemicals were estimated for the Katsunuma population; 0.0529-0.2722 for malathion, 0.0492-0.1603 for prothiophos, and 0.0469-0.1696 for fenitrothion. Contrary to the consistent seasonal tendency towards an increase in mean susceptibility in the fall, reported in the previous study, genetic variances in susceptibility to the three organophosphates did not change significantly in 1997 but tended to increase by 2-to 5-times in 1998. We tested whether both the observed situations, maintenance and increase in genetic variance in organophosphate resistance, can be generated under circumstances in which the levels of resistance to the three organophosphates tended to decrease, by conducting a simulation analysis, based on the hypothesis that resistant genotypes have lower fitnesses than susceptible ones under the density-independent condition. The simulation analysis generally explained the pattern in the mean susceptibility and genetic variances in susceptibility to the three organophosphates, observed in the Katsunuma population of D. melanogaster . It was suggested that the differences in the frequencies of resistance genes in the summer population could affect the patterns in genetic variance in organophosphate resistance in the fall population.

Contributions of three‐site mutations in acetylcholinesterase and cytochrome P450 to genetic variation in susceptibility to organophosphate insecticides within a natural population of Drosophila melanogaster

“…In previous studies, not only did we demonstrate that the dynamics of genetic variation in susceptibility to organophosphates within the Katsunuma population can be sufficiently explained by the fluctuation in the frequency of the resistance factor on the third chromosome of the resistant lines, but we also suggested that genetic variation within the Katsunuma population might also be constructed by other factors, such as various Ace alleles as well as the factor on the second chromosome (Miyo and Charlesworth 2004;Miyo et al 2006). Although the numbers of flies newly collected in the field were small, this study demonstrated that genetic variation in susceptibility to organophosphate insecticides within the Katsunuma population is contributed by several genotypes, produced by at least four Ace alleles as well as cytochrome P450 on the second chromosome, therefore confirming the previous suggestion.…”

“…This concentration of malathion has been shown to kill a majority of individuals of a standard laboratory strain Canton-S (Miyo et al 2000), and the Katsunuma population has been shown to possess genetic variation in susceptibility to 2.5 lg/cm 2 malathion (Miyo et al 2006). To generate various genotypes regarding the three sites, seven isofemale lines established from the population collected on August 4th were mass-cultured.…”

“…3. In a series of studies on genetic variation in susceptibility to organophosphates in the Katsunuma population, it was postulated that resistant-type mutations would decrease in frequency under the density-independent population-growing condition (Miyo et al 2003(Miyo et al , 2006Miyo and Charlesworth 2004). Therefore, one-tailed tests were performed for evaluating significance levels of differences.…”

“…The natural population of Drosophila melanogaster at Katsunuma (Yamanashi Prefecture, Japan) is one of the best-analyzed Drosophila populations in Japan (Hatano et al 1999), and has been shown to possess a wide range of genetic variation in susceptibility to organophosphate insecticides (Miyo et al 2000(Miyo et al , 2001(Miyo et al , 2006. In this study, we attempted to elucidate the resistance factors present in the resistant lines isolated from the Katsunuma population, one on the second chromosome (*II-62) and the other on the third chromosome (*III-50; .…”

The genetic architecture of insecticide resistance within a natural population of <i>Drosophila melanogaster</i>

“…Although Drosophila flies are not recognized as pest species, insecticide selection pressures have been imposed on the Katsunuma population of Drosophila melanogaster (Meigen), owing to management of other pest species [13]. In fact, the Katsunuma population of D. melanogaster exhibited genetic variation in susceptibility to OPs, which was composed of several resistance factors, including a resistant-type AChE and a cytochrome P450 [14,15]. Therefore, it is conceivable that various agents could mold genetic variation within the Katsunuma population, and that the effects of the fluctuations of genetic variation in OPEN ACCESS susceptibility to one class of insecticides within the population could also affect those to other classes of insecticides simultaneously.…”