| This project aims to study how animals, facing severe environments with constrained body design and limited energy supply, solve conflicting physiological demands using phenotypic flexibility at multiple levels of integration. I ask whether and how animals can adjust specific components of their physiological machinery to changes in environmental conditions to balance their energy budget and maximize survival. Throughout the annual cycle, animals face energetically challenging situations. Although it is accepted that they can reversibly adjust behavioral and physiological traits to specific demanding conditions, little is known about the way they cope with conflicting demands on the phenotype. I am studying how red knots use phenotypic flexibility to maximize survival in a context of limited energy supply and constrained body design. I investigates the interactions between two major groups of organs responding to different needs occurring simultaneously in the wild, the digestive system and the pectoral muscles. In the Wadden Sea, wintering molluscivore red knots are digestively constrained by the amount of shell material that can be processed by their digestive organs. This constraint forces the birds to generate and maintain large and energetically expensive digestive systems. Furthermore, when facing cold and windy wintering environments, red knots need to maintain large fat stores for fasting days and large pectoral muscles to maintain adequate levels of heat production through shivering thermogenesis, yet facing limited energy supplies. To make ends meet, the birds therefore have to adjust the different parts of their machinery through physiologically mediated phenotypic trade-offs. In this study, I examine these phenotypic compromises through laboratory experiments and will later scale up the comparison to the contrasting requirements of red knots across their European coastal range. Studying the conflicting demands and the resulting- trade-offs at multiple levels of integration (tissue metabolism, organ size, metabolic rate, thermogenic capacity, hormonal regulation, food intake, locomotor activity as well as behavior), this research aims at a profound understanding of physiological decisions in terms of system development and maintenance in an interpretable context of natural selection. |
