Density effects in population growth: an exploration.

In this paper a heuristic approach is taken to the investigation of density effects in population growth when the limiting factor is food resources. Explicit modeling of resource dynamics lets us to distinguish between density effects that are due to the diminution of the available resources, from density effects arising from direct interference among individuals. While species specific growth dynamics should vary extensively, it is possible to postulate some properties of hopefully, general applicability. This work examines the consequences of three postulates: (a) no growth occurs in the absence of resources; (b) the per capita growth rate increases with available resources; and (c) intraspecies interference competition causes the per capita growth rate to decrease as population density increases. Using these three postulates, I have constructed generalized functional description for each type of density dependence. These functions let us examine interspecies competition in class specific terms. The results indicate that intraspecies interference confers significant advantages in interspecies competition for long term occupation of ecological niches.