Miller Tom E. X.

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Miller
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Tom E. X.
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  • Article
    Sex-biased dispersal and the speed of two-sex invasions
    (University of Chicago, 2011-04-07) Miller, Tom E. X. ; Shaw, Allison K. ; Inouye, Brian D. ; Neubert, Michael G.
    Population models that combine demography and dispersal are important tools for forecasting the spatial spread of biological invasions. Current models describe the dynamics of only one sex (typically females). Such models cannot account for the sex-related biases in dispersal and mating behavior that are typical of many animal species. In this article, we construct a two-sex integrodifference equation model that overcomes these limitations. We derive an explicit formula for the invasion speed from the model and use it to show that sex-biased dispersal may significantly increase or decrease the invasion speed by skewing the operational sex ratio at the invasion’s low-density leading edge. Which of these possible outcomes occurs depends sensitively on complex interactions among the direction of dispersal bias, the magnitude of bias, and the relative contributions of females and males to local population growth.
  • Preprint
    Density dependence in demography and dispersal generates fluctuating invasion speeds
    ( 2017-04) Sullivan, Lauren L. ; Li, Bingtuan ; Miller, Tom E. X. ; Neubert, Michael G. ; Shaw, Allison K.
    Mitigating the spread of invasive species remains difficult—substantial variability in invasion speed is increasingly well-documented, but the sources of this variability are poorly understood. We report a mechanism for invasion speed variability. The combined action of density dependence in demography and dispersal can cause invasions to fluctuate, even in constant environments. Speed fluctuations occur through creation of a pushed invasion wave that moves forward not from small populations at the leading edge but instead, from larger, more established populations that “jump” forward past the previous invasion front. Variability in strength of the push generates fluctuating invasion speeds. Conditions giving rise to fluctuations are widely documented in nature, suggesting that an important source of invasion variability may be overlooked.