In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans.[1] Other examples include humans, the lichen species Parmelia sulcata and the mollusc genus Mytilus.[1] It may result from a broad range of environmental tolerances,[2][3] or from rapid dispersal compared to the time needed for evolution.[4]