Genotype and environment shape the fitness of Drosophila melanogaster

Fitness traits of Drosophila are believed to be expressed under genetic control and the environment. This study focuses on the interaction between the genotype (expressing high and low fitness level) of Drosophila melanogaster and the environment (diet and infection). The environmental factors are supposed to modify traits such as the survival rate, development time, adult dry weight and response to microbial infection. The results indicated that yeast species (nutrients), bacterial infection and the genotype of Drosophila affected the survival rates and the development time of Drosophila. The fit Drosophila produces more survivors and develops faster than the unfit one. The yeast, Pichia toletana induced the highest survival and the fastest development of Drosophila, while Metschnikowia pulcherrima induced the opposite. The origin also had an effect on the development time; the African lines developed faster than the European ones. The yeast species and its concentration appeared to affect the dry weight of Drosophila too. Following infection with Pseudomonas stutzeri, several antimicrobial peptides, such as drosomycin and metchnikowin have been activated in Drosophila adults when they feed on less nutritive yeast (M. pulcherrima). The above mentioned results support the capacity of genotype-by-environment interactions to shape the fitness of D. melanogaster, where the contribution of each factor may differ according to the trait observed and the population under investigation.