PAST AND FUTURE TROPICAL MARINE BIODIVERSITY HOTSPOTS

Hotspots of tropical marine biodiversity are places that harbour disproportionately large numbers of species or species richness compared to the rest of the tropics. Richness and location of these hotspots have changed throughout the Cenozoic era. Here we overview the global dynamics of Cenozoic tropical marine biodiversity hotspots, including the four major hotspots of the Indo-Australian Archipelago (IAA), western Tethys (present Mediterranean), Arabian Sea and Caribbean Sea. Our synthesis supports the ‘Hopping Hotspots’ model, which proposes that locations of peak biodiversity are related to Tethyan faunal elements and track broad-scale shallow-marine habitats and high coastal complexity created by the collision of tectonic plates. A null hypothesis is the ‘Whack-A-Mole’ model, which proposes that hotspots occur in habitats suitable for high diversity regardless of taxonomic identity or faunal elements. Earlier ‘Centre-of’ theories (e.g. centres of origin with diversity decreasing with distance from supposed areas of exceptionally high rates of speciation, for which easy connection to adjacent regions to the east and west is important) were based on the analysis of recent biotas with no palaeontological foundation and may better explain diversity dynamics within a hotspot rather than those between hotspots. More recently, however, human disturbance is massively disrupting these natural patterns. Synthesis effort in paleobiology advances the understanding of tropical biodiversity in the past, present and future.