Meeting Abstract
As environmental conditions change in space and time, they alter fitness through effects on processes including energy acquisition, mechanical performance, metabolic cost, growth rate, survivorship and reproductive output. Organisms can respond by altering their morphology, material composition, physiology and life histories via phenotypic plasticity or by genetic change in populations. Researchers considering the interaction of environmental variables and traits typically concentrate on particular components of fitness, although methods exist to calculate a population level estimate of average fitness, for a set of identical individuals with a designated set of traits. Such models can also estimate future population responses in the field, based on predicted environmental change (e.g. climate change). Components of fitness (performance measures) are not always good predictors of fitness or population response; they can differ in both direction and magnitude. As an example, one set of environmental conditions could maximize growth and lifetime reproduction, but could also result in higher mortality (e.g. wave-induced dislodgment), and thus lower fitness, compared to an energetically less optimal environment. Here, energetics models formulated for growth and allocation are combined with models that calculate population growth rate. Both intertidal and subtidal invertebrates are used as examples, where there is a hypothesized energetic trade-off between shell and attachment production (affecting survivorship), and how energy is allocated toward growth, final size and reproduction. Here, one such model is used to examine effects of environmental variability on fitness, fitness components, and phenotypic variability in critical traits (including body size) and to determine an optimal set of conditions where fitness is maximized.
