Re: Jan's Drosera Dichotomous Key

SCHLAUER@chemie.uni-wuerzburg.de
Tue, 29 Oct 1996 14:36:09

Dear Fernando,

Sorry all you listeners who are fed up with all this stuff and
who have to pay their mailbox bitwise, but there are obviously some
(strange people!) who want to read it. Maybe we should create a sub-
list "cp_jans_weird_views"?

> The fact that bifid styles is synapomorphic in subgen.Drosera, to
> me, suggests exactly that Subgen.Lasiocephala is derived from one of these
> "more advanced" taxa from Subgen.Drosera.

Interesting idea, indeed. The only present representatives of
Subgen.Drosera in or near the range of Lasiocephala are Prolifera,
Arachnopus, and _D.spatulata_ (+ _D.rotundifolia_ in N.Guin, but
this came rather certainly after Lasiocephala). Can you imagine
a descent of Lasiocephala from one of the precursors of these? I have
never considered this possibility but it may be worth a thought.

(...)
> Yes, that's my point. D.meristocaulis has 3 undivided styles.
(...)
> The next natural step would be the styles divided several
> times at the apex as found in many subgen.Drosera taxa in S.Africa and in
> Lasiocephala taxa.
> The only problem is (...several problems mentioned)

I think that the basal bifurcation of the styles in Lasiocephala
and all representatives of Subgen.Drosera is a synapomorphy of these
two subgenera. I.e. they are IMHO younger than those "primitive"
species with basally undivided styles (Thelocalyx, Arcturia,
Stelogyne, Meristocaulis, Regiae). Bryastrum has undivided styles,
while it could IMHO still have arisen from a primitive stock which
has also led to other groups which are nowadays exclusively
represented by taxa with divided styles (I can not think of a better
candidate than Lasiocephala here, but perhaps you have another idea?).

> that in several other groups, including more
> "advanced" ones, we find 3 styles which are only divided near the top,
> and not at the base.

Which group do you mean?

> This is just to say that 3 styles with no subdivision at the base may not
> ALWAYS be plesiomorphic, especially when we look at the complex floral
> morphology of the Aussie Drosera.

Yes, an example is Bryastrum mentioned above.

> BTW, looking at Allen's CPs of Australia Vol.2, he shows that
> D.hamiltonii has 5 styles fused at the base, yet Diels says that there are
> only 3. Which is correct?

I would guess Diels but have to check it. At least I have reserved a
place in the primitive corner for Stelogyne. No problem to shift it
further "downwards". Thanks for highlighting this!

> So anyways, single flowers on short scapes and 3 styles bipartite
> at the base found in D.felix could be seen as a natural intermediate
> between D.meristocaulis (with single flowers and 3 undivided styles) and
> the taxa from Subgen.Drosera with 3 styles bipartite at the base and
> several flowers per scape.

_D.felix_ seems to be very close to _D.kaieteurensis_. I cannot see
any close resemblance with _D.meristocaulis_. Would you think that
_D.acaulis_, _D.felix_, and _D.meristocaulis_ should be grouped
together *just* because they have a reduced peduncle? Once again: Do
not disregard style morphology! It is *essential* in the infrageneric
classification of _Drosera_.

> These are only divided at the tip, though, aren't they?

No. Basally (like all Subgen.Drosera representatives) *and* apically.

> In all
> other species in your Sect.Ptycnostygma, the styles are divided at the
> base and may be further divided near the apex.

Yes.

> >Yes, they are called "stalks", but they are *not* hairs but
> >emergences.
>
> What about the ones on the flower scapes? I believe these are
> hairs and not emergences, correct?

Yes.

> Isn't polen of D.regia considered to be the most primitive
> among Drosera? More than Thelocalyx? Yet if we consider that pentamerous
> led to trimerous Drosera, than how could the more primitive polen be
> explained in D.regia?

Thelocalyx also has a distinctly primitive pollen type (so has
allegedly Arcturia). The tree by Takahashi and Sohma is a hypothesis
based *only* on pollen morphology. Other characters indicate a (only
slightly) different sequence of events. Still I think the
palynological data are very important here (they are useless at the
level of Subgen.Drosera, Bryastrum, Ergaleium & al. because pollen
types 7-8 are ubiquitous there).

> I agree flower color is weak, but you cut out my other comment on
> the erect X ascending scapes.

Sorry! I only have no comment on this. Is it constant?

> Also the leaves are more cuneate in
> D.burmanni and more spathulate in D.sessilifolia.
> Actually, I saw a few D.burmanni forms in Isao Takai's collection
> here in Japan which left me a bit dubious as to whether D.sessilifolia is
> a good species. These D.burmanni were all from Australia, from Allen
> Lowrie's seeds. They were growing side-by-side in different pots, yet same
> soil, and were so surprisingly different from each other! Some were truly
> cuneate, but varied all the way to linear-spathulate!

Interesting. This would be the first amphi-pacific species in
_Drosera_. Still the plants should be kept separate at some rank
because the disjunction is probably an old one.

> Yes, but what I want to know is why you wanted to create a new
> section (add more names to the confusion, as you often say) based on a
> characteristic which is not so reliable

I think it *is* reliable to some degree.

> and which you knew would separate an inhomogeneous section into 2
> inhomogeneous sections.

3 sections if you consider Ptycnostigma.

I think that this has at least created 2 homogeneous sects., viz.
Ptycnostigma (with the "primitive end") and Drosera (with all the
apparently more "advanced" members). I am not entirely
sure about _D.dielsiana_, however. It may have arisen by
introgression of the "primitive" _D.burkeana_ into the "advanced"
_D.aliciae/natalensis_ complex. _D.collinsiae_ may be another such
example. But as even intergeneric hybrids are known in the plant
kingdom, such phenomena do not necessarily invalidate my concept.

The problems in Oosperma (the trash can for all non-Ptycnostigma &
non-Drosera taxa) may necessitate further subdivision but this
should only be done after further study (as it would otherwise only
add confusion to the names).

> >> 10.) As to D.chrysolepis leaf shape, I'd say it's more lanceolate
> >> than spathulate.
> >
> >The key says "oblong spathulate". The important point in the key is
> >that it is decidedly "rounder" than "linear".
>
> I think that's hard to say, it would be somewhere right in the
> middle of both terms, if not more towards linear. The lamina is only
> slightly wider than the petioles and is pointed at the apex. Maybe it
> would be more correct as laceolate-spathulate.

But you still see the difference between _D.chrysolepis_
and _D.villosa_, even if you use my key, don't you?

> As to the info available to you, I was under the impression that
> you had examined Saint Hilaire's type specimens, which includes
> D.ascendens and D.villosa. I also had the impression that you at least had
> read his original description of D.villosa where it does *NOT* say
> glabrous scapes.

Perhaps this should be changed in an update to the key. However, it
would still be helpful if you published your revision first in order
to consider *all* the (rather numerous) pertinent changes.

> Missing one characteristic doesn't mean he didn't see them.

He didn't! Else, he would not have described D.ericksoniae.

> >Yes. BTW "D.ericksoniae" is a synonym.
>
> Of which? D.nitidula subsp.omissa (the true one)?

Yes!

> I'm looking at
> Allen's book now and though there are several similarities between his
> D.ericksonae and D.nitidula, the styles of the former are really very
> unique. If that is the true D.omissa Diels, than maybe that's how it
> should remain, and not among the other taxa considered D.nitidula by
> Allen in his book.

Maybe. But Allen Lowrie himself has decided to reduce Diels' name in
rank.

> BTW, according to his maps, these 4 taxa are all
> sympatric with each other in at least a small area, with the possible
> exception of his D.ericksonae and his D.nit.subsp.omissa.

!

> And since when do the 2 taxa have to be sympatric along their
> whole ranges to be varieties and not subspecies? By what I know, if 2 taxa
> occur together in at least one site, that's enough to put them as var.

Not necessarily. In _Sarracenia purpurea_ there is also a gradual
transition between the two subspp.

> If not, then in how many places do they have to occur together
> to be considered truly sympatric?

It is not the number but rather the geographic pattern. The
geographic distribution pattern of _D.peltata subsp.auriculata_
suggests allopatric speciation (in the E AU part of the range of
_D.peltata_).

> And to complicate the story, we have to
> remember that sympatry is very relative, since often the plants may occur
> in the same geographical region, but are widely separated ecologically and
> never actually grow side-by-side.

And even if they do, there may be barriers to cross-pollination...

> As to your comment on D.insolita being synanthropous

Please cite correctly:"a recent -synanthropous?- range extension"

> , I don't see how that can be possible. In your key you say that it
> differs in having crescentic leaves

This is not a distinguishing but a *common* character with
_D.peltata_. The distinctive features are: bracts dentate apically
(rather weak), cauline leaves rarely developped (very weak).

> You think it could've developed these characteristics in maybe 100
> or 200 years after being brought by British colonists?

Even that would be possible.

> Or when do you suppose it was introduced to Zaire by the aborigenes?

I don't know. But the British were definitely not the first to sail
the Indian Ocean and to cross Africa from one coast to the other.

Kind regards
Jan