Constraints on adaptive mutations in the codling moth Cydia pomonella (L.): measuring fitness trade-offs and natural selection

Abstract

Adaptive changes in populations encountering a new environment are often constrained by deleterious pleiotropic interactions with ancestral physiological functions. Evolutionary responses of populations can thus be limited by natural selection under fluctuating environmental conditions, if the adaptive mutations are associated with pleiotropic fitness costs. In this context, we have followed the evolution of the frequencies of insecticide-resistant mutants of Cydia pomonella when reintroduced into an untreated environment. The novel set of selective forces after removal of insecticide pressure led to the decline of the frequencies of resistant phenotypes over time, suggesting that the insecticideadapted genetic variants were selected against the absence of insecticide (with a selective coefficient estimated at 0.11). The selective coefficients were also estimated for both the major cytochrome P450-dependent monooxygenase (MFO) and the minor glutathione S-transferase (GST) systems (0.17 and negligible, respectively), which have been previously shown to be involved in resistance. The involvement of metabolic systems acting both through xenobiotic detoxification and biosynthetic pathways of endogenous compounds may be central to explaining the deleterious physiological consequences resulting from pleiotropy of adaptive changes. The estimation of the magnitude of the fitness cost associated with insecticide resistance in C. pomonella suggests that resistance management strategies exclusively based on insecticide alternations would be unlikely to delay such a selection process.

Building of an Experimental Cline With Arabidopsis thaliana to Estimate Herbicide Fitness Cost

“…The second group of methods refers to the definition of fitness, i.e., the average per capita lifetime contribution of individuals of a genotype to future generations in this population (Futuyma 1997). It involves the measure of changes in the frequencies of resistance alleles either in isolated populations that are not treated with pesticides over several generations (method 2;Cochran 1993;Boivin et al 2003;Gustafsson et al 2003) or in several connected populations located along a transect between treated and untreated areas (method 3; Lenormand et al 1999). Methods 2 and 3 are the only ones that estimate complete fitness costs.…”

Resistance cost of a cytochrome P450 herbicide metabolism mechanism but not an ACCase target site mutation in a multiple resistant Lolium rigidum population

“…Of course, it is not valid to widely extrapolate from this result as it remains to be established whether the physiological cost accompanying the nontarget site P450-based enhanced herbicide metabolism resistance mechanism observed in this SLR31 L rigidum population is associated with resistance in other L. rigidum populations and other resistant species. With insecticide-resistant insect species, P450-enhanced metabolism has been shown to incur significant resistance costs (Boivin et al, 2003).…”

Mutation in the RmβAOR gene is associated with amitraz resistance in the cattle tick Rhipicephalus microplus

“…Compensatory mutations at second mutational sites may modify the fitness cost and the epistatic effect modulates the overall fitness of the individual (11,12). Nonetheless, fitness costs may be sufficiently high to erode the frequency of the resistance allele in the absence of chemical control (13).…”