Amplification of the Net Reproductive Number by Dispersion for a Matrix Population Model Applicable to the Invasive Round Goby Fish

Matrix population models have proved popular and useful for studying stage-structured populations in quantitative ecology. The goal of this paper is to develop and analyze a general matrix population model that is applicable to the population dynamics of the invasive round goby fish that incorporates both stage structure—larvae, juveniles, and adults—and dispersion. Specifically, we address the issue of whether or not dispersion can amplify the net reproductive number. To this end, we will first review the mathematics of matrix population models with dispersion, particularly those with an Usher demography matrix. Techniques for computing the net reproductive number, like the graph reduction method of de-CaminoBeck and Lewis, will be discussed. A common theme will be the usefulness of submatrices of relevant matrices obtained by the expunging of rows and columns corresponding to non-newborns. Finally, examples will be provided, including the calculation of the net reproductive number for multiple regions using the graph reduction method of de-Camino-Beck and Lewis, examples where dispersion results in a total population flourishing when the populations would otherwise go extinct, and an application to the invasive round goby fish.