The dynamics of adaptation and evolutionary branching Stefan A.H. Geritz Collegium Budapest, Institute for Advanced Studies, Szentharomsag 2, 1014 Budapest, Hungary Stefan.Geritz@zeus.ColBud.hu J.A.J. Metz Institute of Evolutionary and Ecological Sciences, University of Leiden, Kaiserstraat 63, 2311 GP Leiden, the Netherlands Metz@rulsfb.LeidenUniv.nl Eva Kisdi Department of Genetics, Eotvos University, Muzeum krt. 6-8, 1088 Budapest, Hungary Eva.Kisdi@elte.hu Geza Meszena Department of Atomic Physics, Eotvos University, Puskin 5-7, 1088 Budapest, Hungary Geza.Meszena@elte.hu Abstract We present a formal framework for modelling evolutionary dynamics with special emphasis on the generation of diversity through branching of the evolutionary tree. Fitness is defined as the long term growth rate which is influenced by the biotic environment leading to frequency-dependent selection. Evolution can be described as a dynamics in a space with variable number of dimensions corresponding to the number of different types present. The dynamics within a subspace is governed by the local fitness gradient. Entering a higher dimensional subspace is possible only at a particular type of attractors where the population undergoes evolutionary branching.