Genetic Drift, Not Selection, Drives Rapid Feather Color Evolution in Island Bird Radiation
A new study using whole-genome data and detailed plumage measurements from an island bird radiation found that genetic drift — not sexual or ecological selection — is the primary driver of rapid feather color evolution. Researchers observed that rates of color change accelerate as genomic diversity declines, consistent with small, isolated populations undergoing drift. The findings challenge assumptions about the role of selection in speciation and suggest neutral demographic processes can be central to generating biodiversity.
Published as a preprint on bioRxiv, the study examined a complete taxon sample from an insular bird radiation historically important to theories of allopatric speciation, integrating whole-genome sequencing with fine-scale, whole-body plumage coloration data. The researchers tested whether the evolution of signaling traits — specifically feather coloration — covaries with lineage diversification rates and whether selection or drift is the dominant mechanism. They found that lineages with faster rates of color evolution also diversify more rapidly, linking phenotypic change directly to speciation dynamics. Crucially, color evolution rates accelerated as genomic diversity declined, pointing to genetic drift in small, isolated island populations as the key driver rather than strong sexual or ecological selection. This provides one of the first direct empirical links between population demography and macroevolutionary patterns of phenotypic diversification. The results suggest that neutral processes, long considered secondary to selection in shaping signal evolution, may play a central and underappreciated role in island radiations.
What's missing
Key limitations include whether drift-driven color changes are functionally neutral with respect to mate choice, or whether they secondarily acquire selective significance — a distinction the study acknowledges but may not fully resolve. It is also unclear whether the findings generalize beyond island systems to continental radiations.
What different sources said
- bioRxivCenter
Drift drives phenotypic evolution in a rapid island radiation
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