Re: Drosera_evolution

Jan Schlauer (
Mon, 12 Jun 1995 10:25:46 +0100

Hello Arnoud,

>I had just read some related information
>about that, maybe it is interesting for some of you. In the seventies some
>>chemical substances have been isolated from several Drosera species.

Did you read the recent work by Alastair CULHAM (Hi, Alastair!), already
(as you still use obsolete/illegitimate infrageneric names, I have some
doubts)? This is quite interesting and most comprehensive/up-to-date.

IMHO, the presence/absence of certain compounds is a (ONE) suitable
character to check the homogeneity of certain (not all) infrageneric taxa.
Another one being DNA sequence comparisons. However, it is rather difficult
to reconstruct a phylogeny based exclusively on these characters.

The most widespread and most complex sect. Drosera (s.l.) is obviously
inhomogeneous even if judged by morphological criteria (probably
paraphyletic and perhaps of polyphyletic origin), and I do not have a good
theory about the evolution of this one. On the other hand, subgenera
Ergaleium and Bryastrum are rather straightforward and homogeneous
(obviously of monophyletic origin and holophyletic), and (as you may have
noticed) I do have some ideas concerning these...

>Two very interesting examples are D.cistiflora and D.capensis, for they
>have both naphtoquinoses. They might offer us an important clue about the
>evolution of the Drosera's.

As sect. Ptycnostigma (_D.cistiflora_) did rather certainly evolve from an
ancestor common with sect. Drosera (e.g. _D.capensis_, but also the
certainly closely related _D.ramentacea_), and different from the (older)
one common with other sects. like Arachnopus (_D.indica_), the common
occurrence of n & p is not so astonishing (but note the inhomogeneity of
sect. Drosera s.l. in this respect, cf. also additional data by CULHAM!).

Kind regards