Using elasticity analysis of demographic models to link toxicant effects on individuals to the population level: an example

1, A simple two-stage population model was applied to data from a previousl y published life-table response experiment (LTRE), which examined the toxic ity of 4-n-nonylphenol to life-history traits of the polychaete Capitella s p. I. Population growth rates (lambda) and the relative sensitivities (= el asticities) of lambda to changes in each of the individual life-history tra its were calculated. 2. In the present study, the life-history parameters measured in laboratory -reared individuals were manipulated to simulate potential effects of compe tition and predation on fecundity, time to reproductive maturity and juveni le survival to explore how such factors might influence the sensitivity of population growth rate to toxicant-caused changes in individual life-histor y traits. 3. Dramatic changes in elasticity patterns among simulations indicate that population growth rates may respond very differently to toxicant exposure d epending on the extent to which other demographically limiting factors (e.g . competitors and/or predators) are operating on the population, 4, Effectively predicting the population-level consequences arising from to xicant effects measured on individuals can be improved by exploring the ela sticity pattern of a for the population over a range of realistic ecologica l situations.