RUI: Mechanistic Causes and Consequences of Micro-scale Spatial Variation within Intertidal Populations

Loyola Marymount University, Los Angeles CA

Investigators

Abstract

Temperature plays a key role in setting species ranges and driving evolutionary patterns on broad spatial and temporal scales. However, interpretation of the role of temperature in ecology and evolution may be confounded by complex spatial patterns of temperature variation. Within very small coastal intertidal areas, the investigators have documented micro-scale variation in body temperature among individuals that can exceed the average range of body temperature along an entire coastline. Essentially, different organisms experience the same environment in different ways. This micro-scale variation among individuals represents a critical caveat to the conclusion that a number of species currently live close to their temperature tolerance limits; instead, only some individuals do so. It is important to understand the causes and consequences of such micro-scale variation, particularly when attempting to forecast the large-scale outcomes of climatic changes. This project uses the sea mussel as a model system for a combination of field and laboratory studies designed first to answer two mechanistic questions: (1) How does micro-scale variation in body temperature arise, and do individuals use behavioral responses to modify their body temperature based on their recent experience? (2) Is variation in thermal history, the amount of recent heating, correlated with physiological abilities of individuals to combat stress associated with extreme temperatures? The investigators will first quantify the magnitude and the temporal persistence of micro-scale variation in body temperature (a necessity before scaling up to address broad ecological and evolutionary questions) and then link specific biochemical markers of thermal stress in individuals with their unique thermal histories. Finally, the investigators will address the potential sources of micro-scale variation in thermal physiology. Is inter-individual variation a function of variation in recent thermal history, or derived from fixed physiological differences between individuals in warm vs. cool microhabitats, or is individual physiological variation masked in the field by variation in other environmental factors such as food availability or by behavior? Inter-individual variation is an important, understudied aspect of organismal biology. This research will link inter-individual variation in physiology with parallel environmental variation to deepen understanding of evolutionary potential of species to cope with global change. To accomplish this goal, the team will integrate biochemical, behavioral, and biophysical approaches in field and laboratory studies. Importantly, a new understanding will be gained of the oxidative stress mechanisms that may set thermal tolerance costs and limits among species and among populations of a single species. Broader impacts are focused on integration of undergraduate teaching and research by forming a collaboration between Loyola Marymount University [LMU, a Primarily Undergraduate Institution (PUI) with 21% Latino/Hispanic population] and Stanford University. LMU undergraduates will be immersed in summer research at Stanford's Hopkins Marine Station, greatly enhancing their professional development and future career perspectives. A postdoctoral researcher based at LMU will receive PUI-specific professional development in research, classroom teaching, and student mentoring while enjoying access to world-class resources, expertise, and an excellent field site at Stanford. Finally, methods and findings of the research will be incorporated into several undergraduate courses at LMU.