Beetlemania This resource aint big enough for two of us © Steven Begin CC-BY-NC-SA

Darwinian Competition As the species of the same genus usually have, though by no means invariably, much similarity in habitats and constitution, and always in structure, the struggle will generally be more severe between them, if they come into competition with each other, than between the species of distinct genera. (Darwin 1959)

Ecological effects of one species on the other Species 2 +- Species 1 + MutualismPredation - Competition

Competition occurs when two species each require the same limited resource. The availability of the resource to one species is negatively influenced by the presence of the other species. It is a "-/-" interaction. Tribolium confusum Tribolium castaneum Park, Thomas (1948) Interspecies Competition in Populations of Trilobium confusum Duval and Trilobium castaneum Herbst. Ecological Monographs 18(2): Images © Sarefo CC-BY-SA from

Gauses Competitive Exclusion Principle: When two species make similar demands on a limited resource, then one or the other species will go extinct as a result of competition for the resource. In Parks experiments one species won and the other went extinct in every one of the 170 Tribolium competition populations, providing strong support for Gauses principle.

Equilibrium population size when reared ALONE Predict the winner of the competition Climate T. castaneumT. confusum Cold-Dry Cold-Wet Warm-Dry Warm-Wet Hot-Dry Hot-Wet

Equilibrium population sizes when reared ALONE Winner in COMPETITION Climate T. castaneumT. confusumT. castaneumT. confusum Cold-Dry %100% Cold-Wet %70% Warm-Dry %87% Warm-Wet %14% Hot-Dry %90% Hot-Wet %0%

Environment dependence In the Cold-Dry climate, T. confusum eliminated T. castaneum in every two- species replicate. In the Hot-Wet climate, T. castaneum always eliminated T. confusum. Stochasticity In the intermediate environments, each species won in some of the replicates. The outcome of competition is not deterministic.