Jeffrey Walker, PhD
HE | HIM | HIS
- Professor of Biology
Education
- PhD, Anatomy, SUNY Stony Brook
- BA, Geology, University of Pennsylvania
Research Interests
Work in the Walker lab focuses on how functional systems evolve. The evolution of naturally engineered functional systems and human engineered systems are both constrained by trade-offs. For example, kayaks that track well aren't much fun in the surf or white water because of a trade-off between yaw stability and maneuverability. Trade-offs can be mitigated with modular designs. This would be tough with kayaks but the multiple gears of a bike is a good example of a modular design. Modular designs, of course, come with costs. This interplay between costs of modularity v. costs of trade-offs is what makes the evolution of functional systems an interesting focus of study.
The heart of the work is a "general model of functional constraints on phenotypic evolution", whose inchoate form appeared in an NSF dissertation improvement award proposal in about 1991. The vortex of work around this model has spun off side projects in a number of different directions including morphometric modeling, biomechanical modeling of locomotion in fish and fruit flies, and lots of Monte-Carlo simulations to discover best practices.
The core of the "functional constraints model" is the mapping from phenotype to performance (or "form-function mapping"). This mapping requires two things: 1) functionally relevant measures of morphology, which we satisfy with a combination of geometric morphometric variables and biomechanical shape indices, and 2) measures of the ability of organisms to perform fitness-related tasks such as acquiring prey, avoiding predators, and attracting mates. The empirical work in the lab, then, tends to resemble an animal Olympiad. We use Trinidadian guppies, threespine sticklebacks, and, of course, the fruit fly, Drosophila melanogaster, to test various aspects of the functional constraints model.
Dr. Walker joined the Biology Department at USM in 2000 after postdoctoral work at the Field Museum in Chicago. He is a physiologist with expertise in the evolution of functional systems, and his research combines computational and empirical approaches.
Dr. Walker regularly teaches Human Physiology (BIO 221, 223) and Applied Biostatistics (BIO 413/513). He also occasionally teaches the organismal biology course (BIO 107) and the plant and animal physiology course (BIO 109) in the introductory biology sequence, as well as a graduate course in Research Methods (BIO 601).
Selected Publications
McGilvrey, M., Fortier, B., Tero, B., Cooke, D., Cooper, E., Walker, J., Koza, R., Ables, G., Liaw, L. 2023. Effects of dietary methionine restriction on age-related changes in perivascular and beiging adipose tissues in the mouse. Obesity 39: 159-170. doi: 10.1002/oby.23583.
Diamond, KM, Lagarde, R, Griner, JG, Ponton, D, Powder, KE, Schoenfuss, HL, Walker, JA, Blob, RW, 2021. Interactions among multiple selective pressures on the form-function relationship in insular stream fishes. Biological Journal of the Linnean Society 134: 557-567. doi: 10.1093/biolinnean/blab098.
Heathcote, R.J.P., Troscianko, J., Darden, S.K., Naisbett-Jones, L.C., Laker, P.R., Brown, A.M., Ramnarine, I.W., Walker, J., and Croft, D.P. 2020. A matador-like predator diversion strategy driven by conspicuous coloration in guppies. Current Biology 30:2844-2851.
Diamond, K.M., Lagarde, R., Schoenfuss, H.L., Walker, J.A., Ponton, D., and Blob, R.W. 2019. Relationship of escape performance with predator regime and ontogeny in fishes. Biological Journal of the Linnean Society 127:324-336. DOI: 10.1093/biolinnean/blz055
Education
- PhD, Anatomy, SUNY Stony Brook
- BA, Geology, University of Pennsylvania
Research Interests
Work in the Walker lab focuses on how functional systems evolve. The evolution of naturally engineered functional systems and human engineered systems are both constrained by trade-offs. For example, kayaks that track well aren't much fun in the surf or white water because of a trade-off between yaw stability and maneuverability. Trade-offs can be mitigated with modular designs. This would be tough with kayaks but the multiple gears of a bike is a good example of a modular design. Modular designs, of course, come with costs. This interplay between costs of modularity v. costs of trade-offs is what makes the evolution of functional systems an interesting focus of study.
The heart of the work is a "general model of functional constraints on phenotypic evolution", whose inchoate form appeared in an NSF dissertation improvement award proposal in about 1991. The vortex of work around this model has spun off side projects in a number of different directions including morphometric modeling, biomechanical modeling of locomotion in fish and fruit flies, and lots of Monte-Carlo simulations to discover best practices.
The core of the "functional constraints model" is the mapping from phenotype to performance (or "form-function mapping"). This mapping requires two things: 1) functionally relevant measures of morphology, which we satisfy with a combination of geometric morphometric variables and biomechanical shape indices, and 2) measures of the ability of organisms to perform fitness-related tasks such as acquiring prey, avoiding predators, and attracting mates. The empirical work in the lab, then, tends to resemble an animal Olympiad. We use Trinidadian guppies, threespine sticklebacks, and, of course, the fruit fly, Drosophila melanogaster, to test various aspects of the functional constraints model.