DYNAMICS OF AGE-STRUCTURED AND HABITAT-STRUCTURED POPULATIONS

Traditional approaches to modeling population dynamics assume that individual performance (i.e.. fecundity, and survivorship) varies principally according to age/size, and that individuals occupy similar environments. Such an approach is more epiphenomenal than process oriented because performance may vary more between same-aged individuals living in different habitats than between different-aged individuals in the same habitat. One issue addressed in this paper is whether demographic status can legitimately be used as a first-order approximation of individual fecundity/survival. Another is whether age-structured populations exhibit different population dynamics than those structured by habitat. Computer simulations using population projection matrices showed age-structured populations to be more variable and to experience extinction more frequently than habitat-structured populations. This reflects differences in spatio-temporal processes underlying individual performance: in populations structured by habitat. individuals have the ability of changing performance simply by changing habitats, while in age-structured populations performance can only be changed through aging. One means of incorporating habitat structure into demographic analyses is through the use of submodels that account for the distribution of individuals among habitats, followed by habitat-specific analyses of demographics.