Monster Seminar JAM - Is Density-dependence an Evolvable Property? Deriving a Testable Hypothesis and Reporting on Results in Hand
Dr. Joseph Travis, Department of Biological Science, Florida State University
AbstractThe general theory of density-dependent selection predicts that the most fit genotypes in regulated populations will be those with the higher rates of increase at the equilibrium density, which translates, loosely, into those with the higher equilibrium densities. An aspect of this theory that is not widely appreciated is that density-dependent selection can elevate the equilbrium density and decrease the sensitivity of population growth rate to the depressant effect of density, thereby increasing the stability of numerical dynamics as a by-product. This theoretical result offers potential insight into the observed variation among natural populations in the strength of density-dependence and can therefore link two seemingly disparate literatures. There are enough empirical studies of various kinds to indicate that the theory is plausible, for example, studies showing genetic variation in the norm of reaction of fitness to density sensitivity, but only a few laboratory studies of model systems that truly test the idea and no study of natural populations. In this presentation I review this theory and outline the criteria that would be needed to test it and discern its implications. I will argue that populations of the least killifish, Heterandria formosa, fulfill the criteria for a set of natural populations that can offer a fair test. I review the studies of least killifish numerical dynamics and life history that my students, colleagues, and I have been conducting for the last thirteen years and present two experimental studies that test the hypothesis that the strength of density-dependence has evolved to be different in different populations.
University of Washington
Date and Time:
June 1, 2006,
11:00 am - 12:30 pm