Chad Brassil
Chad Brassil
Associate Professor

Ph.D. University of Toronto, 2005
        (Zoology: Ecology)
Ph.D. University of Maryland, 2000
        (Biology)
B.A. University of St. Thomas, 1997
        (Biology & Chemistry)
Contact Information
416 Manter Hall
402.419.0076

 

 

 

Research Interests


I use mathematical tools to address ecological questions from a theoretical perspective as well as a statistical perspective.  My work has crossed systems from plants to predators, from antler flies to Pacific salmon.  My lab constructs general models of ecological systems at the population or community level, but it also includes collaborative work with empiricists on the structure of prairie communities.  In-house, my lab is developing duckweed communities as a flexible empirical system in which to test general theoretical principles.  One of the major themes of my work is addressing the consequences of temporal fluctuations for ecological systems.  This is an important area of investigation because global climate change models predict increasingly variable weather patterns.

 For more information, browse my lab website.

 

Implications of Temporal Variation


I am interested in examining the implications of temporal variation for fundamental ecological theory.  Much of ecological theory has been developed with the assumption that populations will reach stable equilibria over the long term.  However, environmental conditions fluctuate with time and are predicted to undergo increased fluctuations by global climate models.  I examined how temporal fluctuations in the environment alters the indirect interaction in a simple three-species food web, two prey and a shared predator (Brassil 2006).

Besides environmental fluctuations, population sizes may fluctuate due to population interactions such as predator-prey interactions.  Interaction-driven fluctuations can result in a wide range of population dynamics and have important consequences for species co-existence (Abrams, Brassil, and Holt 2003).  The manner in which predators choose between prey can change the type of population fluctuations (Ma, Abrams, and Brassil 2003).  I have found that interaction-driven fluctuations can alter indirect interactions as well as environmental-driven fluctuations (Brassil and Abrams 2004).

My current research is examining mechanisms by which environmental variation might dampen fluctuations in population sizes.  The theoretical work is inspired by the empirical work of Mathew Leibold.

 

Development of Maximum Likelihood Analysis


I have developed maximum likelihood analyses as a powerful quantitative tool linking theoretical hypotheses and empirical data.  Many collaborations have addressed senescence in wild populations, including the first demonstration of senescence in wild insect populations (Bonduriansky and Brassil 2002).  Additional analysis utilized specific distribution functions to uncover important trade-offs between body size and ageing rate in these same wild populations (Bonduriansky and Brassil 2005).  Variation in senescence was examined across multiple wild populations of salmon (Morbey, Brassil, and Hendry 2005).

I developed analytic tools that could examine the serial transfer of pollen from pollinators to flowers but still account for the extremely skewed data that results from clumped, sticky pollen (Castellanos, Wilson, and Thomson 2003).  Currently I am collaborating with Meghan Duffy on a technique to analyze disruptive selection in a wild population of daphnia.

 

Recent Publications


 

  •  Bliss, T., T.O. Powers, C.E. Brassil .  2010.  The spatial influence of aboveground diversity on belowground communities.  Ecosphere.  1:art7.
  • Zajitschek, F., C.E. Brassil, R. Bonduriansky, R.C. Brooks. 2009. Sex-effects on lifespan and senescence in the wild when dates of birth and death are unknown. Ecology. 90:1698-1707.
  • Kawasaki, N., C.E. Brassil, R.C. Brooks, and R. Bonduriansky. 2008. Environmental effects on the expression of lifespan and aging: an extreme contrast between wild and captive cohorts of Telostylinus angusticollis (Diptera: Neriidae). American Naturalist. 172:346-357.
  • Duffy, M.A., C.E. Brassil, S.R. Hall, A.J. Tessier, C.E. C├íceres and J.K. Conner. 2008. Parasite-mediated disruptive selection in a natural Daphnia population. BMC Evolutionary Biology. 8:80.
  • Brassil, C.E. 2007. Temporal variation and the evolution of a parasitoid foraging cue. Oikos. 116:524-532.
  • Brassil, C.E. 2006. Can environmental variation generate positive indirect effects in a model of shared predation? American Naturalist. 167:43-54.
  • Morbey, Y.E, C.E. Brassil, and A.P. Hendry. 2005. Rapid senescence in Pacific salmon. American Naturalist. 166:556-568.
  • Bonduriansky, R., and C.E. Brassil. 2005. Reproductive ageing and sexual selection on male body size in a wild population of antler flies (Protopiophila litigata). Journal of Evolutionary Biology. 18:1332-1340.
  • Brassil, C.E., and P.A. Abrams. 2004. The prevalence of asymmetrical indirect effects in two-host-one-parasitoid systems. Theoretical Population Biology. 66:71-82.
  • Abrams, P.A., C.E. Brassil, and R.D. Holt. 2003. Dynamics and responses to mortality rates of competing predators undergoing predator-prey cycles. Theoretical Population Biology. 64:163-176.
  • Ma, B.O., P.A. Abrams, and C.E. Brassil. 2003. Dynamic versus instantaneous models of diet choice. American Naturalist. 162:668-684.
  • Bonduriansky, R., and C.E. Brassil. 2002. Senescence: rapid and costly ageing in wild male flies. Nature. 420:377.
  • Brassil, C.E. 2001. Mean time to extinction of a metapopulation with an Allee effect. Ecological Modelling. 143:9-16.