Liz Wason has published a second paper from her PhD dissertation, this one in Oecologia.
Wason and Hunter, 2013, Genetic variation in plant volatile emission does not result in differential attraction of natural enemies in the field, Oecologia, DOI 10.1007/s00442-013-2787-4.
Milkweed plants show genetic variation in the amount and composition of volatile organic compounds (VOCs) that they omit (normally and following herbivore damage). Herbivore damage increases the production of VOCs and alters their composition (they are a mix of lots of compounds). Both VOC concentration and blend affect the attack rate of natural enemies on herbivores (in this case predators that bite artificial caterpillars made out of clay). However, all the milkweed genotypes were effective at attracting natural enemies, so the genetic differences in chemical ecology did not translate into genetic differences in plant-herbivore interactions.