The polychaeta species group is characterized by having three dorsocentral setae (most members of the genus Drosophila have only two. This group currently contains a total of 8 species (Baechli,2005), distributed mainly in the Asian tropics. Throckmorton (1975) and Tatarenkov and Ayala (2001) placed the polychaeta group close to the base of the virilis-repleta radiation. Remsen and O’Grady (2002) suggested that this group came out in a clade separate from the remainder of the genus Drosophila, as the sister taxon of the clade formed by Dettopsomyia, Liodrosophila, and Sphaerogastrella. The latter result is consistent with the geographic distributions of these species, but additional work will be required to resolve the placement of the polychaeta species group within the genus Drosophila. Relationships within this group are not well understood, and have yet to be tested with phylogenetic methods.
(excerpted from Markow and O’Grady, 2006, Chapter 1)
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