Date: Tue, 28 Oct 1997 13:58:27 From: SCHLAUER@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4146$foo@default> Subject: Re: D.nidiformis and taxonomy of S.African Drosera
Dear Fernando and all,
> About D.nidiformis, I'm amazed Jan hasn't sent in his comments
> on this plant yet!
You must have written this shortly before I sent these comments (cf.
my previous mail).
> I think there is a possibility D.nidiformis could be a hybrid between
> the short-stemmed green D.madagascariensis and one of the local rosetted
> species, such as D.burkeana, D.natalensis, or D.dielsiana. I did see D.burkeana
> and D.madagascariensis growing together at one place, but no hybrids.
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_).
> It does seem strange to me though that D.nidiformis is so fertile, if
> it truly is a hybrid. Is there any Drosera hybrid which reproduces as well
> from seeds?
I do know only one _Drosera_ hybrid that is sterile, viz. _D.
anglica * rotundifolia_. Because the parents of this have different
ploidy levels (2n=40 and 20, respectively), this sterility is no
wonder at all. The nasty thing about it is that this very hybrid is
the only one to be widespread in Europe and N America, whence the
superstition was deduced that *all* or at least *most* _Drosera_
hybrids should be sterile.
This is not necessarily the case!
> I think it would be probably best, for the moment, to accept
> D.nidiformis as a valid name until it can be sorted out, one way or another. It
> certainly does not seem to belong under D.dielsiana, especially because the
> seeds are fusiform, more like those of D.madagascariensis, whilst D.dielsiana
> has ovoid seeds.
See my previous mail.
> It would be more comprehensive maybe, Jan, if you put it on
> the database as "S = D.madagascariensis X D.dielsiana/natalensis ?".
I cannot see the influence of any other species but _D.
madagascariensis_, and to the latter _D. nidiformis_ is no closer
than _D. affinis_.
> Still on the taxonomy of the S.African Drosera, I spent quite a while
> trying to understand where the borders lay between D.aliciae, D.natalensis, and
> D.dielsiana. Between the 1st two, it seems like geography is the main
> characteristic separating them while the latter two can supposedly be easily
> distinguished by seed and style shape. Considering how variable D.natalensis
> seems to be in the wild, its separation from D.aliciae seems very weak and
> Obermeyer even mentions in his Flora of S.Africa that "...it is sometimes
> difficult to distinguish them in the Eastern Cape where their ranges
> overlap;..."
Correct!
> As I said, it is "supposedly" easy to distinguish D.dielsiana from
> D.alic. and D.natal. because of its ovoid seeds. I had a hard time trying to
> identify a plant in cultivation and in the end could come to no conclusion,
> even with the help of another biologist, Robert Kunitz (Hi Rob, if you're out
> there!). The plants in question are what I called D.dielsiana for years in
> cultivation. They have flat rosettes of reddish spatulate-cuneate leaves, and
> the seeds, to my surprise, were neither ovoid nor as fusiform as those of
> D.aliciae we had available, which were clearly fusiform to the naked eye, more
> than showed by Obermeyer. In fact the 'fusiform' seeds drawn in that paper are
> almost ovoid.
> As to stigma shape, Obermeyer does mention a few differences such as
> spoon-shaped for D.dielsiana, but I am convinced that this is not a
> characteristic to bet your horses on, seeing how variable these are in some of
> the Brazilian taxa I've been looking into, as Jan knows. And the D.dielsiana(?)
> I was analyzing had style shapes more or less intermediate between those
> described for D.dielsiana and D.natalensis in Obermeyer. Quite a messy group!!!
Yes, indeed. There are fairly typical specimens of _D. dielsiana_ in
cultivation, however. They have the styles and seeds of _D. burkeana_
but they lack a petiole entirely. The confusing elements are the
"intermediates". In fact there seems to be a whole scale of gradation
from _D. aliciae_ to _D. dielsiana_, with _D. natalensis_ (and many
other names I do not accept) somewhere in between. The gap between
_D. dielsiana_ and _D. burkeana_ may also melt down in the future if
specimens with semi-distinct petioles will be found. From _D.
burkeana_ the line may be continued all the way towards _D.
madagascariensis_ (with _D. collinsiae_ as a witness). It may well be
that _D. nidiformis_ belongs phylogenetically into this line.
This is probably an example of multiple introgression between
_Drosera_ species with different seed and style morphologies
(another one being _D. spatulata_ / _D. rotundifolia_ in E Asia).
In the S African taxa, different ploidy levels do not seem to be a
problem, and it may be that the true species are only _D. aliciae_,
_D. burkeana_, and _D. madagascariensis_ (i.e. _D. natalensis_, _D.
dielsiana_, _D. collinsiae_, and _D. nidiformis_ representing
transition forms). But it is at least unusual that _D. natalensis_
(and not _D. aliciae_) is found on Madagascar.
> And to add more to this confusion, I could see no major differences
> between D.capensis and D.ramentacea to justify the separation into different
> species. The latter just seems to be a hairier form of the former.
The difference was pronounced enough for all previous authors,
and it seems to be sufficiently constant and distinct to warrant
specific distinction.
Kind regards
Jan
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