Collaborative Research: Understanding the rules of honest signaling

About This Grant

Red feather coloration in the House Finch and other songbirds serves as an honest signal of individual condition. This finding is both well documented and quite remarkable. It is far from obvious why the hue of feathers reveals the individual quality or what prevents low-quality birds from cheating this system. A series of recent breakthrough studies brings us to the doorstep of understanding honest signaling via red feather coloration. We now know key enzymes and transporters responsible for the production and accumulation of red plumage pigments. In the proposed research, a team of scientists with expertise spanning animal physiology, cell biology, and genomics will use both whole animals and cell culture to study the molecular and biochemical mechanisms of coloration. The investigators will examine and compare these processes in House Finches in good or poor condition to deduce the specific mechanisms that promote or inhibit the production and accumulation of red pigments and hence, control plumage coloration. Understanding the biochemical and cellular rules that govern carotenoid coloration in songbirds is important not just for a better understanding of this central process in nature but because carotenoid pigments play a key role in cellular homeostasis in humans. A better understanding of carotenoid systems in birds will inevitably lead to a better understanding of ourselves. The investigators will share these insights and support STEM education through an ornithology summer camp program, curricula development and training workshops for public school teachers, and middle and high school student visits to investigator laboratories. The biochemical, genetic, and evolutionary processed that either prohibit or enable honest communication of information in the context of mate choice remain poorly understood. The proposed research will focus on uncovering fundamental rules of honest signaling by integrating subcellular, cellular, and whole-organism approaches. In birds including the House Finch, high-quality males produce feathers with brighter and redder carotenoid coloration than do low-quality males. Understanding how the condition of individuals affects the function of these genes and hence color expression is the focus of proposed work. The Resource Tradeoff Hypothesis proposes that stress causes loss of red coloration because carotenoids must be diverted away from ornamentation so they can function as antioxidants or immune system enhancers. Alternatively, the Shared Pathway Hypothesis proposes that oxidation of yellow dietary pigments to red ornamental pigments depends on core cellular processes, and particularly cellular respiration in mitochondria, that are sensitive to organism function and environmental conditions. These hypotheses make contrasting predictions regarding the cellular and environmental conditions that will affect ketolation and hence production of red coloration, and we will employ both whole animal and cell culture experiments to test these predictions. The proposed research holds the potential to significantly advance understanding of the ubiquitous links between stress, individual condition, and carotenoid coloration. The experiments that we propose will provide important new insights for how, at a mechanistic level, carotenoid color serves as a signal of condition and hence key insights into a fundamental rule of life—how to keep signaling honest. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.