Ecological specialisation of reef fishes peaks in global biodiversity hotspots

The role off ecological specialization in shaping evolutionary and biogeographic patterns remains unresolved. To date, few studies have quantitatively examined ecological specialization at a global scale, especially for reef fishes. Here, we describe global biogeographic and evolutionary patterns of reef fish specialization. We assemble the largest dataset on reef fish trophic interactions, including dietary information for 5,000 individuals across 387 reef fishes. We add reef fish geographic distributions, using their thermal niche as a proxy for thermal specialization. We reveal that species richness is positively associated with trophic specialization, while isolated reefs are dominated by trophic and thermal generalists. We also reveal a trade-off in specialization: while specialization may be favored in biodiversity hotspots, generalists have a higher colonization capacity and represent an advantageous strategy on isolated reefs. This work sheds new light on the origin and maintenance of fish communities in coral reefs.