Abstract
The current subgenus Drosophila (the traditional immigrans-tripunctata radiation) includes major elements of temperate drosophilid faunas in the northern hemisphere. Despite previous molecular phylogenetic analyses, the phylogeny of the subgenus Drosophila has not fully been resolved: the resulting trees have more or less varied in topology. One possible factor for such ambiguous results is taxon-sampling that has been biased towards New World species in previous studies. In this study, taxon sampling was balanced between Old and New World species, and phylogenetic relationships among 45 ingroup species selected from ten core species groups of the subgenus Drosophila were analyzed using nucleotide sequences of three nuclear and two mitochondrial genes. Based on the resulting phylogenetic tree, ancestral distributions and divergence times were estimated for each clade to test Throckmorton’s hypothesis that there was a primary, early-Oligocene disjunction of tropical faunas and a subsequent mid-Miocene disjunction of temperate faunas between the Old and the New Worlds that occurred in parallel in separate lineages of the Drosophilidae. Our results substantially support Throckmorton’s hypothesis of ancestral migrations via the Bering Land Bridge mainly from the Old to the New World, and subsequent vicariant divergence of descendants between the two Worlds occurred in parallel among different lineages of the subgenus Drosophila. However, our results also indicate that these events took place multiple times over a wider time range than Throckmorton proposed, from the late Oligocene to the Pliocene.
Highlights
The genus Drosophila is the most speciose and intensively studied species assemblage in the family Drosophilidae, yet the genus has long been recognized as paraphyletic since the 1975 report of Throckmorton [1], and this characterization has been confirmed in all subsequent, family-wide phylogenetic studies [2,3,4,5,6]
The other clade comprised 35 species belonging to nine species groups
The clade including the quinaria + guttifera groups was split into two subclades with high confidence; one was comprised of D. angularis, D. brachynephros, D. curvispina, D. unispina, D. phalerata, D. falleni and D. innubila, and the other of D. quinaria, D. tenebrosa, D. deflecta, D. subpalustris, D. recens, D. transversa, D. nigromaculata and D. guttifera
Summary
The genus Drosophila is the most speciose and intensively studied species assemblage in the family Drosophilidae, yet the genus has long been recognized as paraphyletic since the 1975 report of Throckmorton [1], and this characterization has been confirmed in all subsequent, family-wide phylogenetic studies [2,3,4,5,6]. The revised subgenus Drosophila includes 21 species groups [6], of which 15 have been regarded as members of the immigrans-tripunctata clade [4] They are widely distributed mainly in the northern hemisphere, with four species groups endemic to the Old World (the ancora, bizonata, histrio and immigrans groups), 14 to the New World (the appendiculata, calloptera, cardini, ecuadoriensis, guarani, guttifera, lutzii, macroptera, pallidipennis, peruensis, rubrifrons, sticta, tripunctata and xanthopallescens groups) and three distributed in both (the funebris, quinaria and testacea groups). Some of them, such as the funebris, guttifera, quinaria and testacea groups, represent major elements of temperate drosophilid faunas in the northern hemisphere
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