Cryptic microgeographic variation in responses of larval Atlantic cod to warmer temperatures

AbstractAlthough temperature is known to drive species dynamics and distributions, our understanding of the extent to which thermal plasticity varies within species is poor. Differences in plasticity can arise through local adaptation to heterogeneous environments, hybridization, and the release of cryptic genetic variation in novel environments. Here, wild Atlantic cod (Gadus morhua) from contrasting environments inside and outside of a fjord system in southern Norway spawned freely in a semi-natural laboratory environment, generating pure crosses and reciprocal hybrids. A common-garden rearing experiment of the larvae at 6°C, 9.5°C, and 13°C revealed cryptic genetic variation in thermal r…