The cover shows an artistic impression of marine life in Indonesia’s coral reefs. The question of whether there are limits to biodiversity in the seas is typically addressed by examining the fossil record. In this week’s issue, Pedro Cermeño and his colleagues present a model that combines the fossil record with plate tectonics and Earth’s environmental conditions to offer insight into regional diversification of marine invertebrates. The researchers used the model to examine how biodiversity recovered after mass extinctions during the Phanerozoic eon, covering

 some 500 million years of Earth’s history. They found that throughout the Phanerozoic, less than 2% of area of the globe covered by water showed signs of diversity levels reaching saturation. The team also note that as Pangaea broke up into continents, the stability of Earth’s environmental conditions allowed the development of diversity hotspots that helped to drive an increase in biodiversity in the late Mesozoic and Cenozoic eras.