Date: Sat, 01 Nov 1997 17:16:37 +0900 From: ss66428 <ss66428@hongo.ecc.u-tokyo.ac.jp> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4187$foo@default> Subject: Re: taxonomy of Drosera
Jan,
>> How could introgression have happened considering they have
>> different chromossome numbers?
>There is obviously no problem with this. The hexaploid (2n=60) hybrid
can even be crossed with the tetraploid (2n=40) _D. anglica_ to give a
pentaploid (2n=50) plant. There is really much more fertility in this
genus than is assumed by many!
Crossed yes, but the resulting hybrids are infertile and can not be
crossed back with either parent. Thus the 2n=60 D.tokaiensis are not capable
of backcrossing and causing introgression into either D.rotundifolia (2n=20)
nor D.spatulata (2n=40). This is the reason why you *can* say D.tokaiensis is
phylogenetically independent from the original parent species and thus *can*
be considered a good species, although it hasn't spread beyond the area of
occurrence of the 2 parents. Just because a species is not as successful as
others doesn't mean it's not a species.
>Have you seen "D. rotundifolia var. furcata" from China?
No, what is this like? I've only seen D.spatulata from E Asia that are
in cultivation. In fact, have you seen Shing Lam's pictures on his homepage of
D.oblanceolata (?) from Hong Kong? What do think of this species? Except for a few pictures showing plants with longer leaves, it looks pretty much like a D.spatulata to me (although a very beautiful form!). The differences are in the
details, I'm sure.
>It may grow in New Guinea, however...
I remember you mentioned this a few years ago. Have you seen this
collection? Was it found way up on the mountain tops?
>> But you're always telling me that leaf shape and pubescence alone are
>> not sufficient to separate two Drosera as distinct species, even when
>> consistently different!
> Which taxa are you talking about?
Aha! Different standards for different groups. Of course I was refering
to the Brazilian Drosera, which are mostly sect.Drosera and Sect.Oosperma,
which as you know better than anyone else includes most of the S.African
species too, like D.ramentacea. So why should a slight change in leaf shape
and pubescence between D.capensis and D.ramentacea be reason to keep them as
separate species, the same not applying to other species in sections Drosera
and Oosperma?
>The difference between the two _D. peltata_ subspp. is nowhere as fundamental
as between the two sections mentioned.
Why not? What other than seed shape leads you to believe D.rotundifolia
and D.intermedia are much more distantly related than D.auriculata and
D.peltata?
>I just will never buy
that _D. intermedia_ belongs to the same section (or call it series,
or whatsoever) as _D. rotundifolia_, while Ptycnostima should be a
separate subgenus.
I agree with you that these 2 species probably belong in different
section, series, whatever. I'm just trying to understand better your reasons
for going one way or another, that is, how you 'tick':):):) , and hopefully
learn more about these plants along the way...
Best Wishes,
Fernando Rivadavia
Tokyo, Japan
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