Developmental noise and phenotypic plasticity are correlated in Drosophila simulans

Non-genetic variation is the phenotypic variation induced by the differential expression of a genotype in response to varying environmental cues and is broadly categorized into two types: phenotypic plasticity and developmental noise. These aspects of variation have been suggested to play an important role in adaptive evolution. However, the mechanisms by which these two types of non-genetic variations influence the evolutionary process are currently poorly understood. Using a machine-learning-based phenotyping tool, we independently quantified phenotypic plasticity and developmental noise in the wing morphological traits of the fruit fly Drosophila simulans. Utilizing a rearing experiment, we demonstrated plastic responses in both wing size and shape as well as non-zero heritability of both phenotypic plasticity and developmental noise, which suggests that adaptive phenotypic plasticity can evolve via genetic accommodation in the wing morphology of D. simulans. We found a positive correlation between phenotypic plasticity and developmental noise, while the correlation between the plastic response to three kinds of environmental factors that were examined (nutrient condition, temperature, and light-dark cycle) was poor. These results suggest that phenotypic plasticity and developmental noise contribute to evolvability in a similar manner, however, the mechanisms that underlie the correspondence between these two types of variation remain to be elucidated. Non-genetic variations consist of phenotypic plasticity and developmental noise, and these variations have been suggested to influence the direction and rate of phenotypic evolution. However, the role of phenotypic plasticity and developmental noise in the evolutionary process is still poorly understood. In this study, we examined the broad-sense heritability of plasticity and developmental noise, as well as the correlation between the degree of plasticity in response to three kinds of environmental factors and between the degree of plasticity and developmental noise in wing size and wing shape in Drosophila simulans. We found that phenotypic plasticity and developmental noise were heritable and positively correlated with each other, while the correlation between plasticity induced by different environmental cues was poor. Our results suggest that phenotypic plasticity and developmental noise may affect the direction and rate of phenotypic evolution in a similar manner.