The age structured lottery model

The age structured lottery model

The lottery model of competition between species in a variable environmental has been
influential in understanding how coexistence may result from interactions between
fluctuating environmental and competitive factors. Of most importance, it has led to the
concept of the storage effect as a mechanism of species coexistence. Interactions
between environment and competition in the lottery model stem from the life-history
assumption that environmental variation and competition affect recruitment to the adult
population, but not adult survival. The strong role of life-history attributes in this
coexistence mechanism implies that its robustness should be checked for a variety of
life-history scenarios. Here, age structure is added to the adult population, and the
results are compared with the original lottery model. This investigation uses recently
developed shape characteristics for mortality and fecundity schedules to quantify the
effects of age structure on the long-term low-density growth rate of a species in
competition with its competitor when applying the standard invasibility coexistence
criterion. Coexistence conditions are found to be affected to a small degree by the
presence of age structure in the adult population: Type III mortality broadens
coexistence conditions, and type I mortality makes them narrower. The rates of
recovery from low density for coexisting species, and the rates of competitive exclusion
in other cases, are modified to a greater degree by age structure. The absolute rates of
recovery or decline of a species from low density are increased by type I mortality or
early peak reproduction, but reduced by type III mortality or late peak reproduction.
Analytical approximations show how the most important effects can be considered as
simple modifications of the long-term low-density growth rates for the original lottery
model.

Authors: Dewi, S.; Chesson, P.

Topic: life history,mortality,fecundity,measurement,models,environment,competition,invasion,analysis

Publication Year: 2003

Source: Theoretical Population Biology 64: 331-343


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