[Taxacom] Drosophila melanogaster name change?

Kim van der Linde kim at kimvdlinde.com
Fri Apr 9 06:09:42 CDT 2010


Francisco,


On 4/9/2010 7:25 AM, Francisco Welter-Schultes wrote:
> Kim,
>> The case can be solved by creating a mega-genus Drosophila
>> containing many species, probably more than the currently included
>> 1500 species, so D. melanogaster would keep its genus-species
>> combination. This is the responsibility of taxonomists.
>
>> Yes, that is an option, which would generate a genus with 2250+
>> species, and with more than 100 secondary homonyms in need a new
>> species name. Talk about a nightmare.....
>
> Well, this is basically the same problem you had confronted the
> Commission with.

No. The commission was asked to rule about the nomenclatorial aspect, 
namely whether Sophophora melanogaster is appropriate when we revise the 
genus. They have no business to decide about taxonomy or phylogenetics. 
The only question remaining now is when we revise the genus, not if.

> The Commission had to decide, should or should they
> not distort the nomenclature of 1100 species of the funebris
> subgroup?

Again no. The genus is going to be split in four major clades. The name 
of the species in two clades, together 628 species, will change 
regardless. of the two remaining clades, the clade with funebris 
contains 304 species, the Sophophora subgenus contains 332 species 
(species counts as in original application). So, now that funebris 
remains the type species, the name of 28 more species are going to be 
changed. More over, this decision results in renaming of ALL species for 
which the genome is sequenced (14 species in total), instead of 3.

 > I understood that you do not like to solve problems with
> 800 species that you would have to incorporate to Drosophila in
> addition to those which are currently contained (if you like to keep
> the genus Drosophila for melanogaster).  The Commission did not like
> to be responsible for creating the same problems concerning the
> mentioned 1100 species. Why should the Commission solve a problem
> that you do not like to solve?

The decision to split or lump should be made on rational arguments, not 
be based on the preferred outcome for a few species. If we apply the 
criteria that we use in most cases when circumscribing genera, to 
Drosophila, each species group (about 60 or so) should become a genus. 
Drosophila with regard to other genera is far more heterogeneous and far 
older with the basic split between the two main clades (Sophophora + 
Loridphosa +Hirtodrosophila duncani versus sg Drosophila + sg 
Dorsilopha, + sg Siphlodora + Hirtodrosophila s.s + Mycodrosophila + 
Zaprionus + Samoaia + Liodrosophila + Dettopsomyia + Dichaetophora + 
Scaptomyza) at around 50 million years ago. If we would apply the same 
criteria to the other genera in the family, we would have to lump most 
genera together in just a few large genera.

> The Commission decided to let you take this decision yourself.

Then the commission has missed something, the only thing holding up the 
revision was the decision of the commission.

 > If
> taxonomists create such problems, sometimes they must find
> responsible solutions themselves. You still do have alternatives how
> to proceed, including ways to conserve the genus Drosophila for
> melanogaster by taxonomic means.

See above.

> There is also another way to proceed.
>
> Names were initially invented for the purpose of communication.
> You can publish your studies on phylognetic relationships within this
> group without taking conclusions concerning the change of generic
> names.

Done already. One published in 2008, the infamous 'unpublished' 
analysis, and a second being in press right now.

> No official document says that a generic name must refer to a
> monophyletic unit. This is just a currently widely accepted dogma.
> But it is a dogma. You do not need to follow it. There is no
> objective definition for a genus, as Mayr (1942) proposed it for the
> species. You can also say "we know that as a result of our
> studies Drosophila is likely to represent a polyphyletic genus. But
> we decided to keep using that generic name in the traditional sense
> for not distorting current usage in genus-species combinations of
> well-known organisms".

Basically, examine the phylogeny, but leave the taxonomy as is to 
preserve the name.

> These things are decisions you as taxonomists have to take.

Agreed.

> In the garden snail Helix aspersa we have the same problem. Known
> under this name until the 1990s, then taxonomists argued that the
> genus Helix was inappropriate and proposed to place the species in
> either Cryptomphalus, Cornu or Cantareus. This poor species is
> currently known under 4 generic names and 3 different gender
> declinations. Helix still being by far the most frequently used one.

And that is what we tried to avoid. Unfortunately, the commission did 
not see it as a sufficient problem.

Kim




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