Date: Mon, 3 Nov 1997 07:29:33 From: SCHLAUER@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4209$foo@default> Subject: Re: taxonomy of _Drosera_
Dear Fernando,
> 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).
How can you say this? IMHO this is sufficient evidence to prove that
_Drosera_ hybrids are fertile or may at least become fertile. If the
_D. spatulata_ * _D. rotundifolia_ hybrid managed to become fertile
once, why should it not be able to repeat just this?
> 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.
This is your opinion. I think D. * tokaiensis is no less a hybrid
than the (still sterile) D. * obovata. In any event is the
identity in the chorological behaviour between these two *hybrids*
much more evident than the rather circumstantial and not at all
conclusive similarity of the hybrids to the entirely independent
(yet hybridogenic) species _D. anglica_.
> >Have you seen "D. rotundifolia var. furcata" from China? >
> No, what is this like?
Like introgression of _D. spatulata_ into _D. rotundifolia_.
> 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 beautifu
(Don't forget to press your return key once in a line!)
> details, I'm sure.
I do not know what was the context of your original message but _D.
oblanceolata_ differs in a few important details from even the most
extraordinary variant of _D. spatulata_. 1. It is obviously
heterophyllous (two distinct classes of leaf lengths within a single
rosette). 2. The styles are multipartite and widest near the apex
(in _D. spatulata_ the styles are only basally bifurcate and widest
near the base).
> > >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?
I do not know at which altitude the specimen (only one collection
known) was collected. I have not seen it personally, but the
knowledgeable Australian _Drosera_ expert Barry J. Conn has compared
the specimen directly with European ones and with _D. spatulata_, and
he could not find a difference between the New Guinea plant and _D.
rotundifolia_, while it was definitely not a _D. spatulata_.
> 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?
Again, which taxa do you mean, specifically? I do not know of any
taxon as constantly distinct from another species as _D. ramentacea_
from _D. capensis_ that was not accepted as a separate taxon by
myself.
> >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?
The seed shape difference between the two subspecies of _D. peltata_
simply is not as fundamental as the constant and large differences
between _D. rotundifolia_ (fusiform, reticulate) and _D. intermedia_
(ovoid, papillose). The above cited expert writes: "(...) the shape
of the seeds of _D. peltata_ varies from more or less ellipsoid
(the usual shape) to oblong-cylindrical. When the seeds are oblong-
cylindrical, they are difficult to distinguish from those of _D.
auriculata_ which are narrow-linear to oblong-cylindrical." So we
have two widely overlapping ranges of shapes (no way a real
*difference*) in this case. Besides seed shape, there is of course a
large set of additional characters (phytochemical, chorological,
morphological) separating _D. rotundifolia_ from _D. intermedia_.
Kind regards
Jan
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