RE: Manmade Species?

From: Fernando Rivadavia-Lopes (
Date: Fri Oct 08 1999 - 15:45:22 PDT

Date: Fri, 8 Oct 1999 19:45:22 -0300
From: "Fernando Rivadavia-Lopes" <>
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
        artificial, manmade.

Best Wishes,

Fernando Rivadavia Sao Paulo, Brazil

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