Multiple origins of Hawaiian drosophilids: Phylogeography ofScaptomyzaHardy (Diptera: Drosophilidae)

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AbstractScaptomyzais a highly diversified genus in the family Drosophilidae, having undergone an explosive radiation, along with the Hawaiian‐endemic genusIdiomyiain the Hawaiian Islands: about 60% of 269Scaptomyzaspecies so far described are endemic to the Hawaiian Islands. Two hypotheses have been proposed for the origin and diversification of Hawaiian drosophilids. One is the “single Hawaiian origin” hypothesis:ScaptomyzaandIdiomyiadiverged from a single common ancestor that had once colonized the Hawaiian Islands, and then non‐HawaiianScaptomyzamigrated back to continents. The other is the “multiple origins” hypothesis: HawaiianScaptomyzaandIdiomyiaderived from different ancestors that independently colonized the Hawaiian Islands. A key issue for testing these two hypotheses is to clarify the phylogenetic relationships between Hawaiian and non‐Hawaiian species inScaptomyza. Toward this goal, we sampled additional non‐HawaiianScaptomyzaspecies, particularly in the Old World, and determined the nucleotide sequences of four mitochondrial and seven nuclear genes for these species. Combining these sequence data with published data for 79 species, we reconstructed the phylogeny and estimated ancestral distributions and divergence times. In the resulting phylogenetic trees, non‐HawaiianScaptomyzaspecies were interspersed in two Hawaiian clades. From a reconstruction of ancestral biogeography, we inferred thatIdiomyiaandScaptomyzadiverged outside the Hawaiian Islands and then independently colonized the Hawaiian Islands, twice inScaptomyza, thus supporting the “multiple origins” hypothesis.