Population genomics of the island thrush elucidates one of earth's great archipelagic radiations

Andrew Hart Reeve*, Graham Gower, José Martín Pujolar, Brian Tilston Smith, Bent Petersen, Urban Olsson, Tri Haryoko, Bonny Koane, Gibson Maiah, Mozes P.K. Blom, Per G.P. Ericson, Martin Irestedt, Fernando Racimo, Knud Andreas Jønsson

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


Tropical islands are renowned as natural laboratories for evolutionary study. Lineage radiations across tropical archipelagos are ideal systems for investigating how colonization, speciation, and extinction processes shape biodiversity patterns. The expansion of the island thrush across the Indo-Pacific represents one of the largest yet most perplexing island radiations of any songbird species. The island thrush exhibits a complex mosaic of pronounced plumage variation across its range and is arguably the world's most polytypic bird. It is a sedentary species largely restricted to mountain forests, yet it has colonized a vast island region spanning a quarter of the globe. We conducted a comprehensive sampling of island thrush populations and obtained genome-wide SNP data, which we used to reconstruct its phylogeny, population structure, gene flow, and demographic history. The island thrush evolved from migratory Palearctic ancestors and radiated explosively across the Indo-Pacific during the Pleistocene, with numerous instances of gene flow between populations. Its bewildering plumage variation masks a biogeographically intuitive stepping stone colonization path from the Philippines through the Greater Sundas, Wallacea, and New Guinea to Polynesia. The island thrush's success in colonizing Indo-Pacific mountains can be understood in light of its ancestral mobility and adaptation to cool climates; however, shifts in elevational range, degree of plumage variation and apparent dispersal rates in the eastern part of its range raise further intriguing questions about its biology.
Original languageEnglish
JournalEvolution Letters
Issue number1
Pages (from-to)24-36
Number of pages13
Publication statusPublished - 2023


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