on the contrary, sympatric speciation can be more rapid when a species has multiple small demes. this rapid speciation is both observed in plants and vertebrates. rapid speciation is explained by the ecology and social structure of demes. species that behave more territorial, live in patchy environments and/or have a polygynous breeding system with only one reproductive male tend to have smaller deme sizes. interbreeding between small demes is rare due to these factors. furthermore, alleles fixate more rapid in smaller demes. small demes could, therefore, become genetically distinct from each other.