Wanderlust World Wanderlust World The scenario that best illustrates oceans as barriers rather than highways: marine life evolving independently in different ocean basins.
Why: Vast ocean expanses prevent dispersal and gene flow between populations. Over evolutionary time, isolated groups diverge into distinct species.
Example: Coral reef fish families (butterflyfish, angelfish, wrasses) have different species complexes in the Pacific, Atlantic, and Indian Oceans—each adapted to local conditions, unable to cross deep-water barriers.
This vicariance pattern—geographic isolation driving speciation—is a cornerstone of marine biogeography. Oceans connect along coasts and currents, but across basins, they're walls.