Geographic variation for tissue-specific developmental plasticity in natural Drosophila melanogaster populations
Phenotypic plasticity plays a significant role in adaptation, especially in animals that are exposed to heterogeneous habitats. Exposure to different environmental conditions during development can yield varying morphologies through a process called developmental plasticity. Previous studies in Drosophila have shown that temperature and nutrition during development affect body size, but each organ responds to environmental conditions in a unique manner. However, whether there are population differences in organ-specific developmental plasticity remains unclear.
To investigate whether local adaptation to temperate and tropical environments affects the evolution of developmental plasticity, we estimated the effect of temperature and nutrition on wing and femur size in Drosophila melanogaster populations from Maine and Panama City. Population lines were reared at either 21C or 25C on standard lab food or diluted nutrient poor food.
Through dissecting and measuring the femurs and wing lengths of males and female flies, we concluded that wing and femur size is consistently smaller at lower temperatures. In addition, we found that wings are generally more sensitive to temperature changes while femurs are more sensitive to changes in nutrition, consistent with previous studies (Shingleton et al., 2009). These patterns suggest that developmental plasticity of body size evolves in an organ-specific manner in natural D. melanogaster populations.
Comparing males and females of both populations, we observed that plasticity can evolve in a sex-specific manner. This is noted in the increased plasticity response to starvation that is displayed by the females of the temperate population. Given that this increased plasticity response is only observed in the temperate population, we also conclude that the temperate population appears to be more sensitive to changing conditions than the topical population.