In biogeography, geodispersal is the erosion of barriers to gene flow and biological dispersal. Geodispersal differs from vicariance, which reduces gene flow through the creation of geographic barriers. In geodispersal, the geographical ranges of individual taxa, or of whole biotas, are merged by erosion of a physical barrier to gene flow or dispersal. Multiple related geodispersal and vicariance events can be mutually responsible for differences among populations. As these geographic barriers break down, organisms of the secluded ecosystems can interact, allowing gene flow between previously separated species, creating more biological variation within a region.