Diversification dynamics in the global radiation of gobies

The pace of evolutionary diversification varies among groups, between environments, and over geologic timescales. Radiations may be linked to phenotypic innovations and ecological opportunity but for highly diverse groups the factors contributing to accelerated diversification are often less clear. We examine the dynamics and drivers of diversification in gobies, an exceptionally species-rich group with a cosmopolitan distribution in aquatic habitats that exhibits extensive ecological variation coupled with low phenotypic diversity. We establish their evolutionary timescale using a phylogenomic hypothesis of relationships calibrated with multiple fossils and identify a pronounced increase in diversification rate in the clade containing Gobiidae and Oxudercidae. This shift is correlated with both phenotypic and ecological traits; elevated diversification is found among marine lineages and those on reefs as well as in those possessing a fused ventral pelvic disc, a key innovation that facilitates stability on benthic substrates. Our analyses additionally reveal diversification fluctuations at the Eocene-Oligocene transition and in the mid-Miocene, periods of extinction and recovery in global marine habitats. Achieving even near-complete taxon sampling is unlikely in hyperdiverse groups such as gobies, but we show that evolutionary dynamics may still be reliably inferred with less than complete taxon sampling by validating our diversification shift patterns using completely sampled, stochastically resolved trees and confirming the robustness of our rate estimates across congruence classes.