Evolutionary compromises to environmental toxins: urea and ammonia tolerance in Drosophila suzukii and Drosophila melanogaster

Drosophila suzukii is an invasive species, and a serious agricultural threat. Unlike other Drosophila, females of D. suzukii lay eggs under the skin of fresh fruits, through morphological and behavioral adaptations. Therefore, larval development and exposure to pathogens result in damage of a wide range of small and stone fruits. The more innocuous Drosophila melanogaster lays eggs in fermented fruits and larvae develop in a crowded environment characterized by accumulation of nitrogenous waste such as ammonia and urea. Behavioral avoidance cannot prevent larval exposure to environmental toxins, so physiological mechanisms evolved to cope with these compounds. While it is known how D. melanogaster responds to high concentrations of urea and ammonia, little is known on the potential effects on D. suzukii. We investigated the impact of different concentrations of these compounds on fecundity and larval development in both species. Females and larvae of D. suzukii showed a greater sensitivity to high concentration of nitrogenous waste, with a drastic decrease in fecundity and egg viability. Adaptation to a different ecological niche has allowed larvae to develop in a safer and healthier environment. However, metabolic adaptations to different food and environment have probably resulted in less efficient detoxifying and excretory mechanisms.