The origins of tropical marine biodiversity

Recent phylogeographic studies have overturned three paradigms for the origins of marine biodiversity. (i) Physical (allopatric) isolation is not the sole avenue for marine speciation: many species diverge along ecological boundaries. (ii) Peripheral habitats such as oceanic archipelagos are not evolutionary graveyards: these regions can export biodiversity. (iii) Speciation in marine and terrestrial ecosystems follow similar processes but are not the same: opportunities for allopatric isolation are fewer in the oceans, leaving greater opportunity for speciation along ecological boundaries. Biodiversity hotspots such as the Caribbean Sea and the Indo-Pacific Coral Triangle produce and export species, but can also accumulate biodiversity produced in peripheral habitats. Both hotspots and peripheral ecosystems benefit from this exchange in a process dubbed biodiversity feedback.

► Recent phylogeographic studies overturn several assumptions about speciation in the sea, indicating a prominent role for divergence along ecological partitions rather than geographic isolation. ► Oceanic archipelagos and other depauperate regions are not evolutionary graveyards, but can generate and export biodiversity. ► Marine biodiversity hotspots both export and import fauna from peripheral areas in a synergistic process named biodiversity feedback.