Date: Fri, 31 Oct 1997 11:21:14 From: SCHLAUER@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4175$foo@default> Subject: Re: taxonomy of _Drosera_
Dear Fernando,
> > I cannot see the influence of the ovoid-seeded species (if _D.
> > dielsiana_ or _D. burkeana_ were involved, the seeds should become
> > less fusiform, as they do e.g. when these species hybridize into _D.
> > natalensis_).
>
> Are there any proven hybrids between these rosetted species? With all
> that variation how can you be sure, unless they were made in cultivation?
You may call them intermediate or transitional specimens. Of course
their hybrid nature could only be proved by caryological studies
(as has been done with D. * tokaiensis by Kondo).
> And are the seeds of D.nidiformis/sp."Magal." equally as fusiform as those of
> D.madag.? Even if yes, that still leaves space for a D.madag.X D.natalensis
> cross resulting in something similar to D.nidif./sp."Magal."
This would almost certainly result in repeatedly divided styles
(inherited from _D. natalensis_). Please, do *not* use the confusing
terminology "D.nidiformis/sp.Magaliesberg"! I have seen specimens
of non-nidiformis material in cultivation under the name
"Magaliesberg". The latter "name" is invalid and the two are
at least not always the same. Why merging things when one element is
typified and unabiguous while the other isn't even a name?
> (...) We've discussed this one before, but I still do not
> understand why you won't accept D.tokaiensis as a valid species simply because
> it seems to be of more recent origin than D.anglica and still has not spread
> as much.
Because the hybrid is not independent phylogenetically from either
parent (it does only occur where the two parents occur together),
while _D. anglica_ has a much wider range than the non-rotundifolia
parent in the meanwhile.
> Anyways, do you believe that the variation observed in D.spatulata in
> Asia is a result of introgression with D.rotundifolia?
No. At least not all of the variation. The hybrids/introgression
products are more or less clear intermediates from regions where both
species occur, while the variability within _D. spatulata_ affects
populations without any obvious connection to _D. rotundifolia_.
> 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!
Even _D. lanata_ (?n=19) does produce viable seeds. Don't ask me how!
> And also the
> variation observed in the E Asian D.spatulata doesn't seem to be intermediate
> between it and D.rotundifolia.
Have you seen "D. rotundifolia var. furcata" from China?
> In fact the D.spatulata I've seen which look
> the most like D.rotundifolia was one of the several N.Zealand forms, maybe a
> diploid like D.rotundifolia, but the latter does not grow anywhere near NZ.
It may grow in New Guinea, however...
> 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?
> Although there are much more pronounced differences
> present, you've suggested clumping the petiolaris-complex taxa into 1 species.
In this complex, we are at least made believe up to now that the
differences are constant. Wait a few years until all intermediates
are described as new species...
> Not to mention that you consider D.auriculata a subsp. of D.peltata, even
> though both have completely different seed shapes, a characteristic
> you always mention to be so important in Drosera, using it even to
> create section Oosperma and distinguishing it from section Drosera.
> Double standards??
Do you have better standards to offer? The difference between the two
_D. peltata_ subspp. is nowhere as fundamental as between the two
sections mentioned. Anyway, if you can propose a better solution to
the problem of subdividing the horribly polytypical section _Drosera_
s.lat., I am certainly open for suggestions. 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.
Kind regards
Jan
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