Individual variation and ecotypic niches in simulations of the impact of climatic volatility

Expectations of the impacts of climatic variation on species can depend on whether and how intraspecific variability is incorporated in models. Coefficients of variation from tree-ring records of Pinus albicaulis through time and across space were used to parameterize volatility and individuality, respectively. The records across sites were used to differentiate the average modes on an environmental gradient for Gaussian fitness of ecotypic niches, and to add further individual variation in mode and standard deviation of these functions in individual-based Monte Carlo simulations of reproduction and mortality with inheritance of individual variability. Ecotypic gamma and Shannon diversity decreased with volatility included, however, the decreases were mitigated by niche differentiation, but not individual-level variability. Increasing climatic volatility may threaten biodiversity, but less so if a species has ecotypes as represented by ecotypic niches in the model. The results illustrate the usefulness of these parameterizations and of simulations versus analytical solutions.