Competition among freshwater clades explains cave colonization in blind cavefishes

Competition among entire clades is widely thought to shape macroevolutionary trajectories, yet direct tests have relied almost exclusively on paleontological evidence. Here, we present phylogenetic comparative interaction methods (PCIMs) for evaluating historical inter-clade competition. We apply this approach to North American cavefishes, an iconic system characterized by repeated transitions into subterranean habitats. Integrating dated phylogenies with comparative reconstructions of diversification dynamics (testing whether diversification bursts in other clades align temporally with cave colonization) and body shape and size, geography, and trophic ecology, we quantify ecological overlap between amblyopsids and co-occurring freshwater fish clades, then synthesize these axes into an integrated ranking of putative competitors. Our results identify darters as the most consistent ecological competitors across dimensions, whereas other clades show high similarity along isolated axes. By demonstrating how inter-clade competitive signatures can be extracted from phylogenies of living taxa, this study provides a generalizable framework for testing macroevolutionary ecological interactions.