Endothermy is at the heart of the evolutionary success of mammals and birds, allowing them to become adapted to a very broad range of ecological conditions. The endogenous production of heat, even at rest and in the absence of muscular contraction, is tightly linked to mitochondrial proton leak which favours the conversion of food into heat at the expense of ATP production, and by extension of reproduction and growth. Beside its important role in energy balance, mitochondrial uncoupling appears also to limit mitochondrial ROS production at the benefit of long term health and survival. Because mitochondrial uncoupling is enhanced in response to cold exposure, we propose the novel ‘rate-of-heating hypothesis’ suggesting that in endotherms adaptation to the cold selects for greater (basal and induced) mitochondrial uncoupling, resulting in lower mitochondrial efficiency and production of ROS, that in turn favour the evolution of the frequently reported slower life-history trajectories in organisms at higher altitudes and closer to the poles.
Using wild derived voles as study system, we propose (i) to perform artificial selection experiment to test for the existence of genetic correlations between heat production and life history traits such as growth rates, and (ii) to perform common garden experiments associated with measurements of mitochondrial functioning to examine how genetic adaptation to altitude and environmental adaptation to cold shape changes in mitochondrial functioning (i.e. Oxygen consumption, ATP production, ROS production).
This proposal should shed new light on the role of mitochondrial proton leak in the evolution of animal paces-of-life, with the aim to reveal poorly understood connections of biological and medical importance between energy homeostasis, free radical production and growth or life expectancy. It builds on a novel hypothesis suggesting links between the evolution of endothermy, adaptation to cold climate and shifts in the rate of ageing.