Seasonal acclimation and latitudinal adaptation are of the same magnitude in Mytilus edulis and Mytilus trossulus mitochondrial respiration

Abstract

Species distribution models often assume homogeneous physiological performance within a species distribution range. This assumption potentially underestimates the distribution as it neglects physiological plasticity and adaptation among species and populations. Better knowledge on the physiological variation is, therefore, needed to better predict the effects of global warming on species distribution. Mussels in the genus Mytilus are known to display latitudinal variation in whole animal aerobic metabolism. Here we test the hypothesis that latitudinal variation in whole animal metabolic rate of two congeners of Mytilus (Mytilus edulis collected 56°N, and Mytilus trossulus collected 77°N) is related to differences in mitochondrial respiration. We further investigated the changes in mitochondrial respiration following long-term cold-water acclimation of M. edulis. We assessed mitochondrial respiration after five months of acclimation to 1 and 15 °C. At similar experimental temperatures, mitochondrial respiration in animals acclimated to 1 °C was higher compared to those acclimated to 15 °C. After five months of acclimation, 1 °C-acclimated M. edulis had similar mitochondrial respiration as 1 °C-acclimated M. trossulus despite their different geographical origin. Our data indicate that mitochondrial capacity does not support latitudinal observed differences in whole animal metabolism between M. edulis and M. trossulus. However, we reveal that mitochondrial respiration in M. edulis can increase by 283% after cold acclimation. Combined, our results show that seasonal variation in mitochondrial respiration is of the same magnitude as large-scale (>1000 km) latitudinal variation. The high respiratory plasticity in Mytilus spp. improves fitness in changing temperature environments and supports their large biogeographic distribution.