Critical daylength experiment

Critical daylength experiment of Pararge aegeria from five Swedish population

Data from: Diapause induction and relaxed selection on alternative developmental pathways in a butterfly

1. Seasonal phenotypic plasticity entails differential trait expression depending on the time of season. The facultative induction of winter diapause in temperate insects is a developmental switch mechanism often leading to differential expression in life history traits. However, when there is a latitudinal shift from a bivoltine to univoltine life cycle, selection for pathway-specific expression is disrupted, which may allow drift towards less optimal trait values within the non-selected pathway. 2. We use field- and experimental data from five Swedish populations of Pararge aegeria to investigate latitudinal variation in voltinism, local adaptation in the diapause switch, and footprints of selection on pathway-specific regulation of life history traits and sexual dimorphism in larval development. 3. Field data clearly illustrated how natural populations gradually shift from bivoltinism to univoltinism as latitude increases. This was supported experimentally as the decrease in direct development at higher latitudes was accompanied by increasing critical daylengths, suggesting local adaptation in the diapause switch. 4. The differential expression among developmental pathways in development time and growth rate was significantly less pronounced in univoltine populations. Univoltine populations showed no significant signs of protandry during larval development, suggesting that erosion of the direct development pathway under relaxed selection has led to the loss of its sex-specific modifications

Life history traits experiment

Life history traits experimen

Field observation data

Field observations of Pararge aegeria at five locations in Sweden for years 2004-201

Life history traits experiment: Protandry

Life history traits experiment: Protandr

Data from: The evolution of alternative developmental pathways: footprints of selection on life-history traits in a butterfly

Developmental pathways may evolve to optimize alternative phenotypes across environments. However, the maintenance of such adaptive plasticity under relaxed selection has received little study. We compare expression of life history traits across two developmental pathways in two populations of the butterfly Pararge aegeria where both populations express a diapause pathway but one never expresses direct development in nature. In the population with ongoing selection on both pathways the difference between pathways in development time and growth rate was larger while the difference in body size was smaller compared with the population experiencing relaxed selection on one pathway. This indicates that relaxed selection on the direct pathway has allowed life history traits to drift towards values associated with lower fitness when following this pathway. Relaxed selection on direct development was also associated with a higher degree of genetic variation for protandry expressed as within-family sexual dimorphism in growth rate. Genetic correlations for larval growth rate across sexes and pathways were generally positive, with the notable exception of correlation estimates that involved directly developing males of the population that experienced relaxed selection on this pathway. We conclude that relaxed selection on one developmental pathway appears to have partly disrupted the developmental regulation life history trait expression. This in turn suggests that ongoing selection may be responsible for maintaining adaptive developmental regulation along alternative developmental pathways in these populations

DataDryad JEB_2012

Raw data for all analyses excluding individuals that died before pupation or did not follow the expected developmental pathway (see paper for details)