Date: Mon, 22 May 2000 16:22:05 +0000 From: schlauer@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1612$foo@default> Subject: re: Fossil Site / Ancient Relatives
Dear Ivan,
> Fossil evidence for any CP and their possible ancestors is quite rare. It
> is better that we compare the different groups of CP to living relatives.
It would be better to consider *all* evidence available (both fossil
and recent).
> I can make an educated guess as to what these possible fossil ancestors
> of Sarraceniaceae may be like.
But such guesses can easily be overthrown by a single fossil.
> Others have suggested that this family may be close to the greater
> Heath family and allies. (...)
Yes, but genetic data suggest an even closer relationship to
Roridulaceae. There is very little resemblance between the two
families, and I do not know anyone who would have made the educated
guess that they are related from a superficial comparison of the
plants (i.e. not of their genes or of their secondary metabolites).
Fossil evidence is admittedly scant in this case, but morphological
data alone would certainly be misleading.
> Sundew Ancestors?
> Some researchers have suggest that Droseraceae is kin to the family
> Caryophylaceae which includes the Catchflies, genus Silene
Do you have a reference? On which observations was this suggestion
based? A very interesting point!
> I have dissected the Scarlet Catchfly from here in California.
> This plant has sticky glandular trichomes and does capture insects. The
> plant is similar in many features when compared to Drosophylum
The gland structure is much simpler in _Silene_, and these organs
(in Caryophyllales) are quite certainly not homologous to the
glandular structures (Licopolian glands) in Nepenthales. The fact
that they are sticky is the only remaining similarity.
> , the most primitive sundew,
I have tried in previous messages to make clear why I think that
_Drosophyllum_ is not a sundew. There are more differences than
similarities, and _Drosophyllum_ does not even belong to the same
family, i.e. it is less closely related to _Drosera_ than to
_Triphyophyllum_, and even _Dionaea_ is closer to _Drosera_!
> also the flower arrangement is the same.
The inflorescence structure is quite different (although the
fundamental cymose type of both is common in Caryophyllids). The
flower structure is quite different. _Silene_ has a free central
placenta, while placentation in _Drosophyllum_ is basal. Anyway,
floral morphology is very variable within Nepenthales, and
similarities of any type may be due to convergence. Just consider the
even sympetalous condition in Plumbaginaceae (which are more closely
related to Drosophyllaceae than Caryophyllaceae are).
> Coincidently?
Quite probably.
> all Catchflies share the same basic chromosome count as Drosophylum, 2n =
> 12. I don't know if Drosophylum and Silene are in fact related
They are (both are caryophyllids, as far as genetical/chemical data
are reliable). But there are additional families in between.
> but I would say that Silene is at least representative of a link between
> CP and nonCP.
>From a structural/functional viewpoint this is certainly true.
Kind regards
Jan
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