Genomic and geographic diversification of a "great-speciator" (Rhipidura rufifrons).

This article investigates the genomic and geographic diversification of the Rufous Fantail (Rhipidura rufifrons), a bird complex considered a "great speciator" due to its rapid differentiation across the southwest Pacific despite high dispersal ability. Using thousands of single nucleotide polymorphisms (SNPs) from 89 individuals representing 19 taxa, the study identified seven genetically distinct lineages within R. rufifrons, with evidence of gene flow between geographically isolated populations and discordance between plumage variation and genetic relationships. The findings suggest a recent radiation (1.35–2.31 million years ago) characterized by rapid phenotypic differentiation and multiple independent lineages, supporting the classification of R. rufifrons as a great speciator. Biogeographically, the Louisiade Archipelago appears to have played a key role as an early stepping stone in diversification, while remote island populations such as those in the Northern Mariana and Santa Cruz Islands show unexpected sister relationships, highlighting complex colonization and gene flow patterns across the Pacific.