Re: [aroid-l] self pollination of aroids
- Subject: Re: [aroid-l] self pollination of aroids
- From: "Julius Boos" firstname.lastname@example.org
- Date: Tue, 20 May 2003 05:28:30 -0400
----- Original Message -----
From: "Marc Gibernau" <email@example.com>
Sent: Monday, May 19, 2003 9:49 AM
Subject: Re: [aroid-l] self pollination of aroids
Dear Marc and Friends,
Thank you for your most informative and interesting comments! I think we
both agree completely without realizing it! I am not an expert on these
matters, but was trying to determine/illustrate that apomixis was at least
as good and perhaps better than self-pollination, as perhaps there was more
and different genetic material available in apomixis for continued and later
cross-pollination in a population of plants that were started by just one
good seed originally produced from cross-pollination, but growing all by
itself in a remote area. I thought that perhaps reproduction by apomixis
(vs. cross-pollination) until there were a few plants in this new population
to enable cross-pollination to begin may be 'the better of two evils' as it
were, but obviously not as 'good' as cross-pollination in a large and
thereby very genetically variable population.
>>>>>Dear Julius, and Friends,
I have many comments on your last message.
You are right Julius, there are two phenomena :
self-pollination, that is the fertilization of ovules by its own pollen
that will consequently lead to the formation of seeds.
Apomixis that will lead to the formation of (viable) seeds without any
fertilization (e.g. no pollen needed) by "parthenogenesis/parthenocarpy" of
some cells (you have about 10 kinds of apomixis according to the kind of
cells implied: egg-cell, endosperm,.).
In the first case, two genetic informations are mixed whereas in the second
just one genetic information is duplicate.
As you mention for Urospatha and Xanthosoma acutum, may not present
self-pollination as you observe that protogyny is complete (no overlap).
Then apomixis is certainly present in these taxa. The best way to test it
(without counting chromosomes) is to castrate (part of) inflorescences to
see if just female flowers can produce seeds. In my recent study of
Montrichardia (for those interested see attached file), I observe that
bagged inflorescences produced seeds, but I was not able to distinguish
between self-pollination and apomixis. Such answer needs a specific
I suspect that apomixis is common in horticultural aroids as it's the case
for many other families. Fig trees are a good example: about 700 varieties
of Ficus carica, the edible fig, created by men. Half of them are
parthenocarpic, they produce mature figs with (or not) seeds, but without
the fig wasp pollinators (no pollen needed); the other half is more
"traditional" and needs to be pollinated by the fig wasps (carrying pollen)
in order to get mature figs. Consequently parthenocarpic fig species can be
cultivated in areas outside the natural range of the fig wasp.
I don't know if it's better to self-pollinated or to reproduce by apomixis,
in the first case genetic recombination can occur and can create some
variability, but inbreeding can cause low seed set. Some apomictic Rubus
species which are self-fertile have developed in a second step
Apomixis occurs in many taxa thus it must advantageous in some situations.
In many cases, its origin may be from sexually sterile hybrid polyploids
(with high genetic diversity).
Assured reproduction (seeds formation) in absence of pollination (sexual
partners) or/and pollinators.
Clonal reproduction equivalent of vegetative reproduction
'Cost of meiosis' and the mother genetic contribution 100% (instead of 50%)
to her offspring
Fix and disseminate an extremely fit genotype.
Accumulate disadvantageous mutations
Inability to recombine novel mutants
A very narrow niche/habitat
No adaptation to stable habitats (often weeds in transitory habitats).
You thoughts were right except may be about which system is more
I don't know if it helps!!!!