How many niches does a community offer? How is it that the trees seemed to have just enough foliage diversity to accommodate all of MacArthur’s species of warblers? Or, is a niche concept built strictly on ecology somewhat tautological? Ecological niche concepts generally provide systematic ways for describing an organism’s attributes and natural history. But, the extant species become synonymous with available niches. Here, we model an evolutionary niche concept using game theory and the concept of evolutionarily stable strategies (ESS).
We define the Darwinian Niches as those strategies (=species) that are global peaks on the adaptive landscape and that are convergent stable in the sense that natural selection will drive the species’ strategies to these peak. We define Niche Archetypes as all configurations of strategies that are convergent stable. When the Darwinian niche comprises 5 species there will often be a niche archetype for 1, 2, 3 or 4 species but not for greater than 5 species. These niche archetypes may place species at convergent stable minima or at local but not global maxima of the adaptive landscape. When the Darwinian niches are not filled the system can often support 2 to 3 times as many species as the number of Darwinian niches. This occurs when species possess strategies that straddle peaks of the adaptive landscape. Such communities can be ecologically persistent but they are not evolutionarily stable. Evolution will force species out. The evolutionary niche concept of our model predicts and captures many of the salient principles and hypotheses sought after by theories of limiting similarity, assembly rules, niche packing, and niche coevolution. Furthermore, a concept for evolutionary niches applies directly to questions of invasive species, predictions of empty niches, and the maintenance of biodiversity.