Are Structured Life Histories Really Buffered Against Environmental Change?

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Demographic research seeks to understand the links between vital rates of organisms, i.e. patterns of mortality, growth and reproduction, and the growth or decline of their populations. In ecological terms, linking life history data with population dynamics can allow us to manage populations for conservation, pest control or harvesting. In evolutionary terms, links between vital rates and fitness determine the action of natural selection, and have promoted the evolution of an incredible diversity of life cycles and life histories among plants and animals.The environment in which plants and animals live is an unpredictable place, and it is changing rapidly. How do species protect themselves against this unpredictability and change? How do they evolve to cope? One of the most important and well-supported theories in population ecology, the Demographic Buffering Hypothesis, states that the best way to cope is to buffer the most important parts of the life cycle against this environmental variation. For example, the population dynamics of frogs might be most sensitive to the survival of mature individuals, but less sensitive to the annual production of frogspawn. If this is true, then frogs should evolve to make sure mature individuals are resistant to annual fluctuations in weather and temperature, at the expense of similar resistance in egg production.The Demographic Buffering Hypothesis has found support in the analysis of annual fluctuations in rates of survival, growth and reproduction in a wide variety of organisms, from plants to mammals to fish and even corals. However its assumption, that "variation" is "bad for" fitness, is flawed. Furthermore, statistical patterns in vital rate variation means that the evidence base could be found simply by inventing life histories that have NOT evolved to be buffered in any way. The goal of this project is to PROPERLY ask whether wild species have evolved so that their mnost important vital rates are buffered against changes in their environment.Our study resource is a global database of thousands of demographic models of hundreds of species of plants and animals. We aim to convert this database into a searchable web-database, available to scientists and public alike.Our overarching goal is to try to make sense of the bewildering array of plant and animal life cycles, to find patterns and to use these patterns to (a) design management strategies that will help us to exploit natural resources sustainably, and (b) predict the endangered and invasive plants and animals of the future.