Date: Fri, 8 Oct 1999 19:45:22 -0300 From: "Fernando Rivadavia-Lopes" <email@example.com> To: firstname.lastname@example.org Message-Id: <aabcdefg3492$foo@default> Subject: RE: Manmade Species?
Hello Ivan and all,
>The coming CPN article will deal mainly with the treatment and
selection process involved with Colchicine use. I felt that the
philosophical details might make an amusing discussion topic here.
So, what is your opinion? Should this new manmade allopolyploid be
elevated to the species status as D.nagamotoi; or should it be kept
at the hybrid level as D. x nagamotoi?
Although I have already shared my views regarding this
privately with Ivan, I'd like to state them here on the
listserv in hopes of helping foment a lively debate on this
interesting issue. But before getting into this, let me
give a little more background for those of you who don't
remember or weren't on the listserv when this was discussed
a while ago (mainly between Jan Schlauer and I).
As Ivan mentioned, D.anglica is believed to be a species
which orginated from a D.rotundifolia X D.linearis cross
which had its chromosome number doubled by a genetic mishap
and then became fertile. D.tokaiensis is a similar case
from Japan. It is apparently a D.rotundifolia X D.spatulata
cross which also became fertile after chromosome doubling.
Here's where we enter murky taxonomical terrotory. While I
consider D.tokaiensis a valid species, Jan does not (Jan
please correct me here if I accidentally put any unwanted
words in your mouth!). There is really no conclusion since
we differ in regards to a few basic taxonomic opinions and
taxonomy is never 100% agreed upon anyways, so no worries.
Jan considers D.tokaiensis simply a fertile hybrid,
basically because it is still geographically restricted to
the range of the two parental species -- unlike D.anglica
which has spread far and wide (especially in comparison with
D.linearis) being present even in places where neither of
the parents are found (like Hawaii).
In my point of view, geography is not the important factor
here, but genetics. Because D.tokaiensis has 2n=60, it
cannot backcross with either D.spatulata nor D.rotundifolia
since the resulting hybrids come out sterile. Therefore it
is a fertile plant which is genetically isolated from its
ancestors (either of the parent species). This (in my
opinion) is enough to consider D.tokaiensis a valid species,
making it irrelevant or not if it had a recent origin and
has not yet spread beyond the range of its parents. But as
I said, this is MY opinion and other taxonomists have other
opinions and all the right to disagree or not.
Now in relation to manmade "species" I'd prefer to see such
plants referred to by a hybrid nomenclature, such as D.X
nagamotoi (and not D.nagamoto), simply because they are
Fernando Rivadavia Sao Paulo, Brazil
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