Meeting Abstract
Organisms may respond to changing environments through phenotypic plasticity or adaptive evolution. In most cases, the two processes will interact to influence phenotypic trajectories, but whether adaptation will lead increased or decreased plasticity will depend on the genetic correlation between trait values and the slopes of their norms of reaction (plasticity), a relationship that is unknown for most traits. To examine the effect of adaptation to heat stress on the plasticity of heat tolerance, we hybridized populations of the crustacean Tigriopus californicus that show divergent phenotypes for heat tolerance, selected for increased tolerance in hybrids, then measured heat tolerance, and the phenotypic plasticity of heat tolerance in selected lines and unselected controls. To test whether changes in phenotypic plasticity are associated with changes in the plasticity of gene expression, we also sequenced the transcriptomes of selected and unselected lines, both under heat shock and at ambient temperatures. We observed increased heat tolerance in selected lines, but also lower phenotypic and gene expression plasticity in response to heat stress. The plastic response to heat stress was highly enriched for hydrolytic and catalytic activities, suggesting a prominent role for degradation of mis-folded proteins in heat tolerance. Our findings have important implications for biological responses to climate change: if adaptation to heat stress reduces plasticity, then plasticity and adaptive evolution will make overlapping, rather than additive contributions to buffering populations from environmental change.
