Genetic variation underlies plastic responses to global change drivers in the purple sea urchin, .

Phenotypic plasticity and adaptive evolution enable population persistence in response to global change. However, there are few experiments that test how these processes interact within and across generations, especially in marine species with broad distributions experiencing spatially and temporally variable temperature and CO. We employed a quantitative genetics experiment with the purple sea urchin, , to decompose family-level variation in transgenerational and developmental plastic responses to ecologically relevant temperature and CO. Adults were conditioned to controlled non-upwelling (high temperature, low CO) or upwelling (low temperature, high CO) conditions. Embryos were reared in either the same conditions as their parents or the crossed environment, and morphological aspects of larval body size were quantified. We find evidence of family-level phenotypic plasticity in response to different developmental environments. Among developmental environments, there was substantial additive genetic variance for one body size metric when larvae developed under upwelling conditions, although this differed based on parental environment. Furthermore, cross-environment correlations indicate significant variance for genotype-by-environment interactive effects. Therefore, genetic variation for plasticity is evident in early stages of , emphasizing the importance of adaptive evolution and phenotypic plasticity in organismal responses to global change.