asexual seed and naphthoquemistry

Jan Schlauer (
Mon, 12 Jun 1995 17:12:58 +0100

John & al.,

>> Flowers can only be important in terms of evolution in species which
>> produce seed sexually.
>Flowers are only important for sexual reproduction

No, at least not always (v.i.). Some sterile taxa of _Drosera_ (e.g.
_D.anglica * rotundifolia_) do produce normal flowers, but they apparently
never produce any viable seed.

>and sexual reproduction is the only way in which genetic variation and hence
>>evolution can occur at the rate it does.

No. It is a way of genetic *recombination*. Variation (as a result of
mutations) and thus evolution is a phenomenon which occurs in all living
things irrespective of their way of reproduction. The *rate* of evolution
is affected by other factors (e.g. isolation, change of environment) as

>Also, as far as I know no-one has ever changed suggested that seed
>result from asexual reproduction.

So let me be the first in your knowledge to do so. The asexual production
of seed is well known as apomixis among botanists (it does occur e.g. in
_Taraxacum_, _Hieracium_, and the _Ranunculus auricomus_-complex). I could
well imagine a species with 19 (!) somatic chromosomes (e.g. _Drosera
lanata_) to produce viable seed (!) by apomixis.

>Keep up the good work

I keep trying.

The source of more recent work on naphthoquinones in _Drosera_ is:
A.CULHAM & R.J.GORNALL, "Taxonomic Significance of Naphthoquinones in the
Droseraceae", Biochem. Syst. & Ecol. 22(5):507-515 (1994)

BTW, plumbagin is 2-methyljuglone (=5-hydroxy-2-methyl-1,4-naphthoquinone),
i.e. an isomer (and possible biosynthetic "alternative") of 7-methyljuglone
(=5-hydroxy-7-methyl-1,4-naphthoquinone). As I have understood them, CULHAM
& GORNALL could not confirm the presence of naphthoquinones in any species
of subgen. Bryastrum (e.g. _D.pygmaea_).

Kind regards