Data from: Temperature-sensitive fitness cost of insecticide resistance in Chinese populations of the diamondback moth Plutella xylostella

Alleles conferring a higher adaptive value in one environment may have a
detrimental impact on fitness in another environment. Alleles conferring
resistance to pesticides and drugs provide textbook examples of this
trade-off as, in addition to conferring resistance to these molecules,
they frequently decrease fitness in pesticide/drug-free environments. We
show here that resistance to chlorpyrifos, an organophosphate (OP), in
Chinese populations of the diamondback moth, Plutella xylostella, is
conferred by two mutations of ace1 – the gene encoding the
acetylcholinesterase enzyme targeted by OPs – affecting the amino acid
sequence of the corresponding protein. These mutations were always linked,
consistent with the segregation of a single resistance allele, ace1R,
carrying both mutations, in the populations studied. We monitored the
frequency of ace1R (by genotyping more than 20 000 adults) and the level
of resistance (through bioassays on more than 50 000 individuals) over
several generations. We found that the ace1R resistance allele was costly
in the absence of insecticide and that this cost was likely recessive.
This fitness costs involved a decrease in fecundity: females from
resistant strains laid 20% fewer eggs, on average, than females from
susceptible strains. Finally, we found that the fitness costs associated
with the ace1R allele were greater at high temperatures. At least two life
history traits were involved: longevity and fecundity. The relative
longevity of resistant individuals was affected only at high temperatures
and the relative fecundity of resistant females – which was already
affected at temperatures optimal for development – decreased further at
high temperatures. The implications of these findings for resistance
management are discussed.