Transcriptome of the ladybird beetle Cryptolaemus montrouzieri fed different diets for several generations

Biological control agents usually suffer from shortage of target prey or hosts in their post-release stage. Some predatory agents turn to attack other prey organisms, which may induce their physiological and further evolutionary changes. In this study, we investigated the life history traits, gene expression and genotype frequency of the predatory ladybird Cryptolaemus montrouzieri during an experimental prey shifts. Ladybirds were either continuously fed by the alternative prey aphids for four generations, or shifted back to initial prey mealybugs in each generation. In general, utilizations of aphids resulted in reduced performances and severe physiological adjustments, indicated by the significant changes in development and fecundity traits and a large number of differentially expressed genes between two prey treatments. Within the aphid-feeding lines, the performances of developmental time, adult weight and survival rate recovered in a certain level in the sequent generations, which might be a result of adaptive evolution. Specially, we detected that shifts back to mealybugs caused gradually increase of fecundity. Correspondingly in the fecundity-related gene vitellogenin, a genotype contained several minor alleles in the initial population became the main one within four generations. Our results explored a short-term experimental evolution of a so-call specialist predator in a prey shift condition. This potential rapid adaptation to novel prey in biological control agents will increase environmental risks associated with non-target effects.