The physiological mechanisms underlying local adaptation in natural populations of animals, and whether the same mechanisms contribute to adaptation and acclimation, are largely unknown. Therefore, we tested for evolutionary divergence in aerobic exercise physiology in laboratory bred, size-matched crosses of ancestral, benthic, normal Lake Whitefish (Coregonus clupeaformis) and derived, limnetic, more actively-swimming ‘dwarf’ ecotypes. We acclimated fish to constant swimming (emulating limnetic foraging) and control conditions (emulating normal activity levels) to simultaneously study phenotypic plasticity. We found extensive divergence between ecotypes: dwarf fish generally had constitutively higher values of traits related to oxygen transport (ventricle size) and use by skeletal muscle (percent oxidative muscle, mitochondrial content), and also evolved differential plasticity of mitochondrial function (Complex I activity and flux through Complexes I-IV and IV). The effects of swim-training were less pronounced than differences among ecotypes and the traits which had a significant training effect (ventricle protein content, ventricle MDH activity and muscle Complex V activity) did not differ among ecotypes. Only one trait, ventricle mass, varied in a similar manner with acclimation and adaptation and followed a pattern consistent with genetic accommodation. Overall, the physiological and biochemical mechanisms underlying acclimation and adaptation to swimming activity in Lake Whitefish generally differ.

R code for nested, two-way ANOVAsR code for nested, two-way ANOVAs (example for Fig. 1A)Figs1-6_MixedEffectsModel_Code.RR_Code_for_DFAR_Code_for_DFA (Fig. 7)Fig7_DFA_Code.RFig1A_HematocritData for Figure 1AFig1B_VentricleMassData for Figure 1BFig2_HeartEnzymesData for Figure 2Fig3A_PercentRMData for Figure 3AFig3C,E_CapillaryDensityData for Figure 3C,EFig4_MuscleEnzymesData for Figure 4Fig5_MitoRespirationData for Figure 5Fig6_ETCenzymesData for Figure 6Fig7_DF(tank_means)Data for Figure 7 - tank means for all significant variables