Life history, wing morphology and reproductive output of Pararge aegeria L. on drought stressed host plants

To create host plants for Pararge aegeria larval rearing, potted plants of the grass species Poa trivialis were grown under standard conditions. Plants were randomly assigned to one of two treatment groups: control or drought-stressed and watered according to protocol. Newly hatched P. aegeria larvae were randomly selected and collected from four different outbred laboratory stock populations that originated from two different landscape types in Belgium: two populations from a deciduous woodland landscape and two populations from an agricultural landscape. The larvae were placed on either control or drought-stressed potted P. trivialis plants and reared in a climate room in common garden conditions until emergence as an adult. The rearing pots were spatially randomized with respect to population of origin and host plant treatment group. To determine how growth on drought stressed host plants differentially affects woodland and agricultural landscape larval development and survival the following data were recorded: total development time (days) and mean egg to adult survival per population. To measure fecundity and egg hatching success, on the day of emergence adult female P. aegeria from each of the host plant treatment groups (control vs. drought stressed) were randomly chosen and placed individually in netted cages along with a potted P. trivialis for oviposition and a male for mating. Fifty females of woodland landscape of origin and 50 of agricultural landscape of origin were set up. To determine whether development on drought stressed host plants differentially affects resource allocation to reproduction in females from woodland versus agricultural landscapes the following data were collected: total number of eggs laid by a female during life, mean lifetime egg size (mm2), and lifespan (days). To determine how growth on drought stressed host plants differentially influences resource allocation to flight morphological traits in both male and female P. aegeria from woodland versus agricultural landscapes, digital images were taken of the dorsal wing surface under carefully controlled light conditions. Using these digital pictures, forewing surface area (mm2), hindwing surface area (mm2), forewing length (mm) and forewing melanization, were measured using the image analysing software Image J 1.38x. Wing loading was calculated as total body weight / total wing area. Mean forewing length and mean forewing surface area were determined for each individual, and these measures were used to calculate forewing aspect ratio: forewing length2/forewing area. For each trait measured, damaged wings were excluded from analyses. Based on repeat measurements of a random subset of 30 individuals, the amount of measurement error because of imaging and digitizing was negligible. Full methods can be found in the manuscript: Gibbs M, Van Dyck H & Breuker CJ. (2012) Development on drought stressed host plants affects life history, flight morphology and reproductive output relative to landscape structure. Evolutionary Applications, volume 5(1), 66-75.