Size-Dependent Mortality Induces Life-History Changes Mediated through Population Dynamical Feedbacks

Abstract

The majority of taxa grow significantly during life history, which often leads to individuals of the same species having different ecological roles, depending on their size or life stage. One aspect of life history that changes during ontogeny is mortality. When individual growth and development are resource dependent, changes in mortality can affect the outcome of size‐dependent intraspecific resource competition, in turn affecting both life history and population dynamics. We study the outcome of varying size‐dependent mortality on two life‐history types, one that feeds on the same resource throughout life history and another that can alternatively cannibalize smaller conspecifics. Compensatory responses in the life history dampen the effect of certain types of size‐dependent mortality, while other types of mortality lead to dramatic changes in life history and population dynamics, including population (de‐)stabilization, and the growth of cannibalistic giants. These responses differ strongly among the two life‐history types. Our analysis provides a mechanistic understanding of the population‐level effects that come about through the interaction between individual growth and size‐dependent mortality, mediated by resource dependence in individual vital rates.