Invasion and coexistence of two phenotypically variable species

The effect of ecological polymorphism on the coexistence of species has not previously been studied. Using a model of competitive interactions within and among species I investigate invasion of both monomorphic and polymorphic species. Three comparisons are considered which place previous work in a broader context and extend it to cover the situations characterized by polymorphism. First, I examine invasion of a monomorphic species into the range of another monomorphic species. This is done in a manner which allows for generalization to the following more complex cases. Second, I examine invasion of a monomorphic species into the range of a polymorphic species. Finally, I examine invasion and coexistence of a polymorphic species in the range of another polymorphic species. This sequence of comparisons produces some simple generalizations concerning invasion and coexistence of species in a variety of ecological situations. Furthermore, it emphasizes polymorphism as a potentially important factor in shaping ecological communities.