# Interspecific competition models and resource inequality between individuals

## TL;DR

This paper shows how a well-known model of interspecific competition can be derived from individual-level resource competition, linking population-level outcomes to individual resource allocation.

## Contribution

The study provides a bottom-up derivation of the Hassell–Comins model from individual-level random resource competition.

## Key findings

- The Hassell–Comins model can be derived from individual-level random resource competition.
- Resource inequality between individuals relates to key parameters determining density dependence in the model.
- The model can describe competition for species with ideal scramble or contest intraspecific competition.

## Abstract

Most classical discrete-time population models of interspecific competition have emerged as population-level phenomenological models with no evident basis at the individual level. This study shows that the Hassell–Comins model, a widely used discrete-time model of interspecific competition, can be derived in a bottom-up manner from a simple model of random resource competition between individuals of two species as an expression of expected population sizes in the next generation. The random competition leads to inequalities in resource allocation between individuals, which are related to the key parameters of the Hassell–Comins model that determine the density dependence of each species. The relationship between population-level parameters, such as intra- and interspecific competition coefficients, and individual-level parameters is discussed in detail, as is how the derived competition equations depend on the degree of inequality within each species. By considering limits of maximum or minimum resource inequality within each species, the derived model can describe interspecific competition for various combinations of two species exhibiting ideal scramble or ideal contest intraspecific competition.