GRAND CHALLENGES Confronting the physiological bottleneck: A challenge from ecomechanics

We begin by giving away our punch line: A lack of physiological insight is the primary impediment to the successful prediction of the ecological effects of climatic change. To be sure, there are uncertainties in our predictions of future climate, especially at the local scale, and the complexities of ecological interactions stretch our ability to model complex systems. But it is physiology— our understanding of how individual organisms function and interact with their environment—that presents the largest challenge. Without a better mechanistic understanding of how plants and animals work, we can never be assured of an accurate warning of what lies ahead for life on earth. SICB’s Grand Challenges for Organismal Biology (Schwenk et al. 2009) accurately highlight many of the current gaps in our understanding of physiology as it relates to ecological prediction. Addressing these challenges will thus serve to advance our quest to predict the ecological effects of variability in climate. To justify these conclusions, let us step back and review a bit of academic history. The field of biomechanics applies the theory and methods of physics and engineering to explain how plants and animals exchange heat, mass, or momentum with their surroundings. At its core, biomechanics assumes a mechanistic, bottom-up approach to science, arguing, in essence, that if one understands the pertinent details of how plants and animals work, one can predict how they will function in any environment. Arguably, biomechanics gelled as a field with the work of Sir James Gray, a zoologist at Cambridge University in England. He applied fluid mechanical theory to the study of aquatic locomotion. (It was Gray who noticed that the power output of dolphins’ muscles appeared to be insufficient to propel them at the speed they are observed to swim, a conundrum known as Gray’s Paradox that continues to garner interest, e.g. Fish 2006.) From Gray, the biomechanical torch passed first to Torkel Weis-Fogh (also at Cambridge) and then (upon Weis-Fogh’s untimely death) to R. McNeill Alexander at Leeds University. Through their research and that of their students—and especially through Alexander’s prolific production of books on the subject— biomechanics expanded from its initial focus on animal locomotion to include elements of materials science, physical chemistry, and structural mechanics. Comparable headway was made in the prediction of organisms’ body temperatures through the application of quantitative heat budget models. In the 1970s and 1980s, this broadened field was consolidated and popularized by three classic texts: Mechanical Design in Organisms (Wainwright et al.1976), Biophysical Ecology (Gates 1980), and Life in Moving Fluids (Vogel 1981). Biomechanics currently stands as a highly successful example of both the mechanistic approach to biology and the potential for interdisciplinary science. Despite the impressive breadth of its subject matter—from bacteria to blue whales, diatoms to red woods, extant to long extinct species (and despite the title of Gates’ tome)—classical biomechanics has traditionally maintained its focus on a single level of