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THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVITY OF POPULATION GROWTH TO SURVIVAL, GROWTH AND REPRODUCTION
Citation:
Gleason, T R., W R. Munns Jr., AND D E. Nacci. THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVITY OF POPULATION GROWTH TO SURVIVAL, GROWTH AND REPRODUCTION. Proceedings of the Conference of Applied Biologists, London England, July 8-9, 1999.
Description:
Matrix population models are often used to extrapolate from life stage-specific stressor effects on survival and reproduction to population-level effects. Demographic elasticity analysis of a matrix model allows an evaluation of the relative sensitivity of population growth rate ( ) to each demographic parameter. When developing a model, choices must be made regarding number of stages, stage durations, and model time step. The tacit assumption has been that model time step does not influence model results. However, to date, there has not been a critical analysis of this assumption. We used data from a published model and developed three models with identical numbers of stages, but differing time step. Our analyses indicated that the three models had very different demographic elasticities. Total reproductive elasticity, summed across all stages, declined markedly with reductions in time step. Clearly, the selected time step can have serious and largely unrecognized implications for model results.