256017.fig.003a
(a)
256017.fig.003b
(b)
Figure 3: Adaptive and nonadaptive reaction norms. These hypothetical examples suppose that the optimum expression level for some gene increases with temperature and that increased temperature induces increased expression of the gene. (a) Plasticity is adaptive when it keeps expression closer to the optimum than it would be if expression, were constant across temperatures. (b) Plasticity is nonadaptive (maladaptive, in this case) when induced changes in a new environment take expression further from the optimum than it would be if it had remained constant. (b) is an example of countergradient variation, in which genetic differences cause cool-adapted genotypes to have higher gene expression than warm-adapted genotypes at the same temperature. The result is overexpression by cool-adapted genotypes transplanted to warm environments.