> > Flowers can only be important in terms of evolution in species which
> > produce seed sexually.
> Flowers are only important for sexual reproduction and sexual
> reproduction is the only way in which genetic variation and hence
> evolution can occur at the rate it does. Also, as far as I know no-one
> has ever changed suggested that seed result from asexual reproduction.
There are plants which produce seeds by parthenogenesis. There
are even salamanders, insects, and others which reproduce assexually, the
male gametes often coming into play just to stimulate the female gametes
and initialize their development (without the male genetic material ever
entering the female gamete). Mendel himself lost interest in his results
from the pea experiments after he tried the same methods on a plant
(which I can't remember the name) which produced part of its seeds from
parthenogenesis, and thus the results were never those nice 1:3, 1:2:1,
etc. which he'd gotten with the peas.
> > The ancestral Drosera in Australia
> > surely didn't know their habitats were shrinking and that they faced
> > almost certain extinction if they didn't adapt to the new conditions.
> Are we talking about Lamark or Darwin. Under Darwinian theory plants do
> not adapt but are selected by virtue of environmental pressures it is a
> passive process. The less constant the environment the more likely
> variation is to occur.
>
> Keep up the good work
>
> John Peacock (john_p@icr.ac.uk)
Sorry, I think I didn't express myself clearly once again. I
thought it was obvious that I was making a Lamarckian statement which
could not be taken seriously. It was supposed to sound ridiculous. I am
still trying to understand what factors were responsible for the evolution
of the Drosera in Australia. If the climate was changing and they suffered
a dry stress which selected those more apt to withstand drier climates,
then how would this differ from the plants growing in drier soils at the
edge of their ideal wet habitats next to a seepage habitat on a mountain
range here in Brazil, for example? You mentioned climate consistency.
Maybe with the climate changes in Australia, the seasons were more
inconsistent (unreliable, unstable, or whatever) than in the Drosera
habitats of South America over the past few million years. Thus the dry
stress would have been greater on the ancestral Drosera in Australia than
on the ancestral Drosera in South America, even on those growing in drier
soils of the transitional habitats around an ideal seepage habitat on a
mountain range in what is now Brazil, for example. Though it was not
ideal in these transition zones and the dry stress was present, at least
we can speculate that it must've been more stable than in the Drosera
habitats of Australia as the climate became drier and the seasons more
inconsistent. How about it Jan?
FERNANDO RIVADAVIA
Sao Paulo, Brazil