Duncan J. Irschick

Research Interests

Functional Morphology, Evolution, and Behavioral Ecology

The research in my laboratory addresses the interface among organismal design, function, and ecology. Broadly, we are interested in the evolution of complex functional systems in all its facets. Our research integrates microevolutionary and macroevolutionary approaches, and we apply both experimental and descriptive approaches to understand the causes of, and ultimately the consequences of this diversity. Among others, some of the methods employed in my laboratory include: phylogenetic comparative methods, ecological mark-recapture techniques, 2-D and 3-D kinematic analysis, analysis of kinetics (force dynamics), and analyses of hormones and morphology. While much of our research has focused on lizards as a model system, we also conduct studies with many other taxa, such as spiders, frogs, snakes, salamanders, and mice, among others.

Some of the questions being addressed in the laboratory are: Which factors drive the evolution of complex systems? Do morphology, behavior and habitat use co-evolve? Which factors limit performance, both in terms of mechanistic factors, as well as behavior? Can we understand a species habitat use based on their functional capacities? How are sexual selection, physiology, and performance related?

We take an integrative approach by incorporating both field-based and laboratory-based methods to address these and other questions. In the field, we conduct ecological experiments, quantify processes of death and reproduction, and observe animals to understand their natural behavior. We conduct laboratory experiments to understand how behavioral aspects, such as male competition and female choice relate to performance capacity. We also take an explicitly mechanistic approach to understand how morphological variation translates into variation in performance, behavior, and habitat use.

One example of my research concerns how species evolve specializations for different habitats by studying their performance capacities, such as maximum bite force, or maximum sprint speed. Such performance abilities can be important in many ecological contexts, such as during interactions with rival males, when capturing prey, or when eluding predators. We are also actively taking more mechanistic approaches for studying organism diversity by examining limits on locomotion in lizards. For example, one area of research has been a comprehensive attempt to understand whether mechanical power output acts as a limiting factor for climbing in arboreal lizards, such as geckos. Many geckos are remarkable climbers, but will also run with large loads that induce high power outputs, and hence offer an excellent model system for understanding whether power limits performance. Future studies will expand beyond lizards to include other animals and humans. We are also taking an evolutionary approach to this issue by examining power output among different species of lizards during different activities (e.g., running and jumping). This approach allows us to address whether species that are good accelerators are also capable of achieving high top speeds.

This research on power output fits into a broader theme of understanding limb function in arboreal specialists, such as Anolis lizards and geckos. Many lizards have independently invaded arboreal environments, and have evolved a series of fascinating morphological and behavioral adaptations, including adhesive toepads, and remarkable behavioral abilities to move on narrow and inclined surfaces. We are interested in testing the functional and behavioral mechanisms by which these species are able to accomplish these tasks, and further, understand how these traits have evolved. Much of our field work is conducted in the Caribbean, such as the islands of Jamaica, Puerto Rico, and the Bahamas to test how these species use different portions of their arboreal habitats. Other research in my lab includes examination of the role of sexual selection in the evolution of performance in lizards, selection on locomotor performance, and force platform analysis of vertebrate movement.

Finally, a new line of research consists of investigating the selective aspects of performance in Caribbean Anolis lizards in a clade of lizards that shows remarkable convergence in morphology and behavior. Do species that have converged similar phenotypes as a result of similar selection pressures also encounter equivalent selective pressures? We are actively investigating these issues by conducting intensive mark-recapture studies linking morphology, performance, and mortality in a diversity of Anolis species.

Representative Publications

Irschick, D.J., Vitt, L.J., Zani, P., Losos, J.B. 1997. A comparison of evolutionary radiations in Mainland and West Indian Anolis lizards. Ecology, 78: 2191-2203.

Irschick, D.J., Jayne, B.C. 1999. Comparative three-dimensional kinematics of the hindlimb for high-speed bipedal and quadrupedal locomotion of lizards. Journal of Experimental Biology, 202: 1047-1065.

Irschick, D.J., Losos, J.B. 1999. Do lizards avoid habitats in which their performance is submaximal? The relationship between sprinting capabilities and structural habitat use in Caribbean anoles. The American Naturalist, 154: 293-305.

Irschick, D.J., Garland, T. Jr. 2001. Integrating function and ecology in studies of adaptation: Investigations of locomotor capacity as a model system. Annual Reviews of Ecology and Systematics, 32: 367-396.

Irschick, D.J., VanHooydonck, B., Herrel, A., Androsceu, A. 2003. Effects of loading and size on maximum power output and kinematics in geckos. Journal of Experimental Biology, 206: 3923-3934.

Ramos, M., Irschick, D.J., Christenson, T. 2004. Overcoming an evolutionary conflict: Removal of a reproductive organ greatly enhances locomotor performance. Proceedings of the National Academy of Sciences, 101: 4883-4887.

Lailvaux, S., Herrel, A., VanHooydonck, B., Meyers, J., Irschick, D.J. 2004. Performance capacity, fighting tactics, and the evolution of life-stage male morphs in the green anole Lizard (Anolis carolinensis). Proceedings of the Royal Society of London, B., 271: 2501-2508.

Irschick, D.J., Ramos, M., Buckley, C., Elstrott, J., Carlisle, E., Lailvaux, S., Bloch, N., Herrel, A., VanHooydonck, B. 2006. Are morphology->performance relationships invariant across different seasons? A test with the green anole lizard (Anolis carolinensis). Oikos, 114: 49-59.

Herrel, A., Huyghe, K., Vanhooydonck, B., Backeljau, T., Breugelmans, K., Grbac, I., Van Damme, R., Irschick, D.J. 2008. Rapid large scale evolutionary divergence in morphology and performance associated with the exploitation of a novel dietary resource in the lizard Podarcis sicula. Proceedings of the National Academy of Sciences, 105: 4792-4795.