Rapid and repeated evolution of the pigmentation patterns in reef fishes

Abstract

Pigmentation patterns are integral to animal biology1-3 and uncovering the mechanisms driving their diversification is essential for determining the evolutionary principles that shape this fundamental aspect of biodiversity4-7. Coral reef fishes are particularly notable for their extraordinary pattern diversity, ranging from simple spots and stripes to intricate, maze-like designs. Despite over a century of investigation, the evolutionary processes that govern the diversification of these pigmentation patterns remain one of the most persistent unresolved questions in evolutionary biology. Here, we investigate the relationship between pattern diversity, species richness, and geography across six iconic families of pattern-diverse coral reef fishes. Utilizing time-calibrated phylogenies, we reveal constant disparity of pigmentation patterns across globally variable reef fish communities8. We find strong evidence for a positive correlation between pattern diversity and species richness, with a high divergence of pigmentation patterns in sympatry that highlights the role of these patterns in speciation and phenotypic differentiation. Moreover, our findings support the stages model of adaptive radiation9, revealing that most pigmentation pattern diversity has emerged in evolutionary history. These results demonstrate that the evolutionary history of pigmentation patterns in reef fishes is characterized by a combination of rapid and constrained phenotypic diversification that has likely played a crucial role in their speciation dynamics.