While adaptive dynamics theory added new perspectives to our understanding of speciation processes driven for example by competition for resource, controversy arises about how to incorporate genetic detail in such models. Simultaneously doing justice to the complexities of ecology and genetics is difficult. Conventional quantitative genetics theory, assuming unimodality of character distribution to derive moments equations, inevitably fails once a population becomes multimodal.

We here propose ‘oligomorphic dynamics theory' to deal with the quantitative genetics with multimodal character distribution. We first decompose the character distribution into the sum of unimodal distributions corresponding to individual morphs. Characterizing these morphs by their positions, widths, and relative frequencies, we derive the coupled dynamics of these quantities. Three stability concepts of character distribution, community stability, convergence stability, and evolutionary stability, are found to correspond respectively to the local stability of morph frequencies, positions, and widths. As first applications of oligomorphic dynamics theory, we derive the effects (a) of the strength of disruptive selection on waiting times until speciation, (b) of mutation on conditions for speciation, and (c) of the 4th moments of competition kernels on patterns of speciation.