Impact of the trophic strategy on the eco-functional diversification of a coral reef fish family

The analyses of the role of trophic strategies as promoter or constraint on processes of diversification remain understudied, especially in fish. The Pomacentridae (damselfishes), a species-rich (394 species) and worldwide distributed reef fish family, include three main trophic guilds: (1) pelagic zooplankton feeders, (2) benthic feeders grazing on turf algae or biting polyps and (3) an intermediate group feeding on zooplankton, small benthic invertebrates and algae.
Our study aims to analyze the role of the trophic strategies in the eco-functional diversity of Pomacentridae. Due to its feeding versatility, we hypothesize that the intermediate trophic group is the most successful group in terms of eco-functional diversity through evolutionary time. To target our aim, we compiled detailed dietary, environmental and behavioral data for 201 pomacentrid species, and compared the eco-functional diversity among trophic guilds. Various metrics, such as functional entity (i.e. unique combinations of functional traits) and functional richness revealed that the intermediate trophic group exhibited the lowest diversity. Then, we used time-calibrated phylogenies and comparative methods to evaluate the impact of trophic strategies on the tempo of ecological diversification. Results were consistent and the lowest rate of diversification was found for the intermediate trophic group. Our study shows that a generalist trophic strategy does not promote ecological diversification but being specialized may increase the ability to evolve greater diversity.