Date: Thu, 30 Oct 1997 17:48:27 +0900 From: ss66428 <ss66428@hongo.ecc.u-tokyo.ac.jp> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4165$foo@default> Subject: Re: D.nidiformis and taxonomy of S.African Drosera
Jan and all,
> The true (?) _D. nidiformis_ is clearly related to _D.
> madagascariensis_ but it differs from it (i.e. also from "D. spec.
> Magaliesburg p.p.") by its much shorter but still distinct petioles
> that are incurved, so the lax rosette becomes distinctly concave. As
> this feature cannot easily be attributed to introgression by _D.
> burkeana_ or _D. dielsiana_, I would not assume that _D. nidiformis_
> is of direct hybridogenic origin.
I think that after a few years in cultivation the inevitable may have
happened: mixed-up seeds. I never noticed any differences between the
D.sp."Magaliesberg" I cultivated and the D.nidiformis I saw in other
collections, always assuming they were the same. The differences you describe
between both could easily be a result of different cultivation conditions.
But then again it could be a result of hybridization of the original
D.sp."Magal.", after it was introduced into cultivation, with some other
species. Remember I said I was able to cross D.nidiformis/D.sp."Magal." with
several African Drosera.....
Anyways what I cultivated as D.sp."Magal." had very long and distinct
petioles, relatively to D.natalensis, D.dielsiana, and even D.burkena plus the
form of D.madagascariensis I've seen in cultivation, which has petioles
shorter or equal to those of D.sp."Mag.". The D.madag. I saw in the wild in
the Pretoria/Jo'berg area had longer and thicker petioles than any of these,
often even canaliculated on the underside.
Considering the variability existing in D.madag., the only thing which
places D.nidiformis apart is its complete lack of stems. As for D.affinis, the
differences described for it in relation to D.madagascariensis (glabrous,
greener, longer petioles) can easily be caused by the fact that it grows in
wetter habitats than D.madagascariensis. I've seen that before with other
species in Brazil such as D.communis......
>> 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_).
Are there any proven hybrids between these rosetted species? With all
that variation how can you be sure, unless they were made in cultivation?
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." The only problem
is that D.nidif./sp."Magal." has petioles narrower than those of D.natalensis
and also narrower than those of the D.madag. native to N S.Africa, comparable
only to those of D.collinsiae. But then this species has wider lamina, ovoid
seeds, and short scapes which could not give rise to something like
D.nidif./sp."Magal." in a cross with the D.madag. form native to N S.Africa.
So for the moment it does seem best to keep D.nidiformis as a valid
taxon. W have to trace
> 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!
The only Drosera hybrids I remember as being fertile were the crosses
I made between D.sp."Magal." and the rosetted S.African Drosera, D.burmanni X
D.sessilifolia, and maybe D.filiformis subsp.filiformis X subsp.tracyi. All
other crosses to my knowledge are either sterile or nearly so. Comments,
anybody?????
> 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).
Multiple introgression between D.spatulata and D.rotundifolia in E
Asia? I guess you're referring to D.tokaiensis, the hexaploid Japanese Drosera
originated from a sterile cross between the diploid D.rotundifolia and
tetraploid D.spatulata which had its cromosome number doubled and became
subsequently fertile, the same situation which is suspected to have occurred
to the ancestor of D.anglica which supposedly origintated from a D.linearis X
D.rotundifolia cross. 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.
Anyways, do you believe that the variation observed in D.spatulata in
Asia is a result of introgression with D.rotundifolia? How could introgression
have happened considering they have different chromossome numbers? And also the
variation observed in the E Asian D.spatulata doesn't seem to be intermediate
between it and D.rotundifolia. 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.
>> 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.
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! Although there are much more pronounced differences
present, you've suggested clumping the petiolaris-complex taxa into 1 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??
Best Wishes,
Fernando Rivadavia
Tokyo, Japan
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