RoL: FELS: EAGER: Metabolic asymmetry: An energetic rule for linking biology across scales

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Ecosystems are composed of animals often referred to as being either 'warm' or 'cold' blooded. While warm-blooded organisms (endotherms) can generate their own body heat, cold-blooded organisms (ectotherms) rely on outside temperatures to determine their internal body temperatures. This difference between organisms can influence how they grow and develop, when they can be active, and the amount of food resources they require. This study explores the role of changing environmental temperatures on the way endotherms and ectotherms evolve and interact with each other. For example, warmer temperatures may cause declines in the hunting success and abundance of endotherms feeding on cold-blooded prey. The goal of this study is to develop general rules about the biology of endo- and ectotherms that can be applied to understand their relationships within and across ecosystems. The results of this study will inform conservation efforts through a focus on how different types of organisms respond to environmental change. The development of general rules that shape life on Earth will be used to engage the public through an on-line film and photo essay, and the development of an interactive website for students and the public to explore how temperature influences species behavior, interactions, and evolution. This work will provide opportunities to mentor and engage undergraduates through research. Although energetic constraints on organismal and ecosystem processes are well recognized, general rules for how individual energetics shape biotic interactions and diversity are rare. This ambitious project addresses this gap in understanding by exploring the energetic basis of movement, foraging, and competitive behavior to derive a quantitative framework for 'metabolic asymmetry'. The work explores how the metabolic differences between antagonistic species drive ecological interactions and shape biodiversity across space and time. Objective I is to derive and develop a general theory of biotic interactions based on metabolic asymmetry that links physiology, behavior, and community ecology. An initial focus will be endotherm/ectotherm interactions, which best exemplify metabolic asymmetries in nature. Objective II will experimentally assess and refine theory using laboratory and field foraging experiments on endothermic shrews (Soricidae), their ectothermic salamander and lizard competitors, and shared ectothermic invertebrate prey. Objective III will explore macroecological and macroevolutionary implications of the metabolic asymmetry theory, by a) assessing metabolic escalation - the progressive increase in metabolic rates - across space for 376 extant species of shrews; b) evaluating metabolic escalation across deep time, using recent phylogenetic methods to reconstruct basal metabolic rates across the tree of life, and c) forecasting ecosystem-level shifts in the relative dominance of endotherms and ectotherms across the globe, given future climate warming scenarios.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.