The Drosophila genus is paraphyletic. That means there are species nested within the phylogeny of the genus that belong to other genera. Or, in other words, there are species descended from the most recent common ancestor (MRCA) of all Drosophila species that belong to different genera. If that doesn’t make sense, just look at the tree.
A paraphyletic genus is a no-no in taxonomy. There are two ways to deal with the problem. First, the genera nested within the Drosophila phylogeny can be redesignated into the Drosophila genus. That’s not going to happen because the genus is too freakin’ big to begin with. The second option is to split the Drosophila genus into multiple genera. The genus is already split into two subgenera, Drosophila and Sophophora. D. melanogaster, the best known Drosophila species, is in the Sophophora subgenus. D. funebris, the type species of the genus (or the one that holds the rights to the name “Drosophila”), is in the Drosophila subgenus. So, if the genus gets split, D. funebris gets to keep the genus name Drosophila, while D. melanogaster will probably be renamed Sophophora melanogaster. That doesn’t sit well with some people.
There’s a movement afoot to ensure D. melanogaster gets to keep the genus name Drososophila, despite historical precedence saying otherwise. I, myself, really don’t care. I guess it would be a bit of an inconvenience if D. melanogaster was renamed S. melanogaster, considering that more papers have been written about D. melanogaster and its close relatives than about the species in Drosophila subgenus.
If this sort of thing gets you going — regardless of the side you’re on — the case has been brought to the International Commission on Zoological Nomenclature (ICZN). The ICZN is like the League of Nations or Super Friends for taxonomists. Anyway, it’s Case 3407 in the Bulletin of Zoological Nomenclature.
More information can be found here.