Testing the role of reefs as a source of evolutionary novelty in the oceans

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Historical and ecological factors are discussed as potential causes of the great diversity of modern tropical coral reefs. In this project I want to explore historical aspects focusing on the question of whether reef diversity is mostly created in situ or if it is largely due to the recruitment of taxa that evolved in other environments. In other words, I intend to evaluate the role of reefs as a source of evolutionary novelty. Several previous analyses have demonstrated that in the oceans substantial evolutionary innovation originated in onshore shallow-water environments and in the tropics. If the loci of evolutionary novelty can be specified more precisely remains unknown, however. Although the great species richness of tropical coral reefs and the high number of sibling species might indicate that evolutionary novelty stems from the reefs themselves, an evolutionary radiation outside the reef environment and subsequent recruitment is also plausible. Data from the Paleobiology Database (listing Phanerozoic taxonomic occurrences in their geological context) and the PaleoReefs database (listing geometric, sedimentological and paleontological attributes of Phanerozoic reefs) will be combined to (1) identify taxa that have a distinct affinity to reefs opposed to taxa that have an affinity to level-bottom ecosystems, (2) compare diversity dynamics of reef lovers and level-bottom lovers, and (3) determine the openness of the reef system to emigration (dispersal) and immigration (recruitment). The analyses will detail the role of reefs in macroevolution over the entire Phanerozoic. In addition to testing for the innovation potential of reefs in general, this project will test if this potential has changed through time, contrasting the Paleozoic with the post- Paleozoic and background extinction intervals with mass extinction intervals. This study will (1) add new perspectives to the loci of evolutionary novelty at several taxonomic levels, and (2) have implications for reef evolution in particular but also for evolutionary processes in general.