My research is primarily focused on how animals use muscle to power locomotion. Locomotion occupies a significant proportion of an animal’s daily activity pattern and the high rate of energy expenditure involved means that few aspects of an animal’s physiology, ecology and behavior are unaffected by its demands.
Previous work has included measurements of the mechanical properties and performance of muscle tissue, and the metabolic costs associated with locomotion. I have worked with both vertebrates and invertebrates, and investigated systems within the three major locomotory modes, swimming, terrestrial locomotion and flight.
Studies of animal locomotion have tended to fall into two categories: those that focus on externally measurable parameters such as oxygen consumption and force generation; and those that measure the characteristics of internal systems such as muscle and tendon. A major aim of work in the lab is to combine these approaches and study locomotory systems in an integrated way.
Top view of a swimming rainbow trout. A. Sequential video stills, midline highlighted in white, numbers show time in milliseconds. B. Isolated sequential midlines. C. Superimposed sequential midlines.
Variation in phenotype and behavior within populations
The diversification of organisms is a central focus of evolutionary biology. Darwin recognized that distinct varieties within a population were potential 'incipient species', an initial step in the process of diversification. Divergent forms within populations are typically assumed to represent adaptation to different habitats. Although the presence of divergent, habitat-specific forms, or ecomorphs, is well documented in many species, their adaptive significance is largely inferred from the potential functional consequences of differences in external morphology, rather than direct measures of performance in ecologically relevant tasks such as locomotion. This is problematic as natural selection acts on whole-organism performance, not morphology per se, and physiological factors can mask apparent links between form and function. Performance data are therefore required in order to assess the adaptive significance of ecomorphological divergence and its potential role in advancing diversification and speciation.
Recent work in the lab has established the presence of morphological divergence in the bluegill sunfish population in Lake Waban. We have also quantified habitat-related differences in multiple aspects of swimming performance: energy economy, maneuverability, maximum speed and differences in diet and feeding behavior. We are currently engaged in detailed analyses of the links between phenotypic and performance variation within the population and the consequences for fitness.
Top view of a bluegill sunfish swimming around a series of vertical, cylindrical obstacles. Video analysis allows the maneuverability of fish to be assessed.
Field swimming performance of fish
A detailed understanding of locomotor behavior in the field is essential if laboratory measurements of physiological performance are to be placed in context with organismal fitness. Measurements of field behavior also ensure that laboratory experiments can be designed to measure ecologically relevant aspects of performance. Current work in the lab is using underwater video camera arrays to quantify fish swimming performance in the field. This approach enables detailed three-dimensional reconstruction of fish trajectories and analysis of propulsive kinematics with a view to refining bioenergetic models of field metabolic rate in fish.