|Danka, Robert - Bob|
Submitted to: Journal of Evolutionary Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/9/2011
Publication Date: 4/1/2012
Citation: Greenfield, M.D., Danka, R.G., Gleason, J.M., Harris, B.R., Zhou, Y. 2012. Genotype x environment interaction, environmental heterogeneity, and the lek paradox. Journal of Evolutionary Biology 25(4):601-613 Interpretive Summary: An important question in evolutionary biology asks why genetic variation is maintained in populations of animals despite selection pressure for favorable attributes in mates. A good example of this occurs for signaling activities by males, where females should choose only the fittest males. Theory suggests that, with certain restrictions (environmental variation in space or time, and some genetic mixing), interactions between genetic types and specific environments allow different behavioral types to excel in different environments. This research addressed the potential role of such interactions in maintaining genetic variance during sexual selection. We measured parameters of ultrasonic courtship calling “songs” of a honey bee pest, the lesser wax moth, in laboratory settings. This animal is a useful model for testing because of genetic population structure and behavior. Genetic lines were created using four neighboring populations of moths, and these were reared under different environmental conditions (warm versus cold) in one year. In addition, genetic lines of one population were reared in consecutive years. Interactions occurred for the various song parameters in the several populations, but this did not occur at a greater frequency between populations than it did within a population. However, for several key song parameters, interactions between genetic lines taken from two different years were greater than between lines from the same year. This suggests that variation through time in sexual selection by this animal is the primary means of conserving variation in response to different environments.
Technical Abstract: Substantial additive genetic variance (VA) often exists for male signaling traits in spite of the directional selection that female choice imposes. One solution to this problem, generally termed the ‘lek paradox’, is that genotype x environment interaction (GEI) occurs and generates a ‘crossover’ of reaction norms in which no one genotype performs in a superior manner in all environments. Theoretical work indicates that such crossover can sustain genetic variance provided that either 1) spatial heterogeneity in environmental conditions combined with limited migration among populations or 2) temporal heterogeneity in environmental conditions combined with occasional generation overlap is present. Whereas some recent studies have revealed the intersection of reaction norms for sexually-selected traits in laboratory and in natural populations, associated information on environmental heterogeneity, migration, and generation overlap has not been investigated. We studied this question in an acoustic pyralid moth, Achroia grisella, in which previous work indicated GEI and crossover of reaction norms for several parameters of the male song evaluated by females. We measured reaction norms for male song as expressed when development was completed under different environmental conditions in four neighboring, yet isolated, populations during one year, and in one of these populations during consecutive years. Crossover occurred for the various song parameters in the several populations, but we did not observe a higher incidence of crossover between genotypes taken from two different populations than from the same population. However, for several key song parameters, crossover between genotypes taken from two different years was higher than between genotypes from the same year. We suggest that temporal heterogeneity in the form of varying selection could potentially conserve VA in A. grisella, but we also note other factors that might contribute.