No signature of selection on the C-terminal region of glucose transporter 2 with the evolution of avian nectarivory

Abstract

Flying birds, especially those that hover, need to meet high energetic demands. Birds that meet this demand through nectarivory face the added challenges of maintaining homeostasis in the face of spikes in blood sugar associated with nectar meals, as well as transporting that sugar to energetically demanding tissues. Nectarivory has evolved many times in birds and we hypothesized that the challenges of this dietary strategy would exert selective pressure on key aspects of metabolic physiology. Specifically, we hypothesized we would find convergent or parallel amino acid substitutions among different nectarivorous lineages in a protein important to sensing, regulating, and transporting glucose, glucose transporter 2 (GLUT2).