From: Jody Haynes webmaster at plantapalm.com> on 2000.06.17 at 00:49:40(4806)
Eduardo,
Yours was an interesting post. I, too, have some knowledge (and an astute
interest) of paedomorphosis and neoteny--but only in animals. I was not
aware of
the process in plants.
I feel that these terms should be clarified. Although they both refer to the
"possession in the adult stage of features typical of the juvenile stage of the
organism's ancestor", neoteny specifically refers to sexual maturation of the
'juvenile' stage: "heterochronic evolution whereby development of some or all
somatic features is retarded relative to sexual maturation, resulting in
sexually mature individuals with juvenile features" (Futuyma, D. J. 1986.
Evolutionary Biology. Sinauer Associates, Inc. Sunderland, MA.).
Thus, paedomorphosis refers to the simple possession of juvenile traits in an
adult organism, but does not specify a process; conversely, neoteny is the
process by which somatic maturation is retarded relative to sexual maturation.
Does this make sense? Anyone else care to comment on this interesting topic?
Jody
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Jody Haynes
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Palm & Cycad Societies of Florida (PACSOF)
Virtual Palm & Cycad Encyclopedias
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Eduardo Goncalves wrote:
> Dear Aroiders,
>
> The production of sexual parts in juvenile individuals is a
> morphogenetic "accident", but it is usually explored by the evolutionary
> history of many groups. There are two morphogenetic processes associated to
> this aspect: Paedomorphosis and Neoteny. Both concern juvenile individuals
> with mature sexual parts or juvenile structures that are kept active in
> adult individuals. These phenomenons occur in both plants and animals. Some
> evolutionists say that humans are just neotenic apes, because our brain
> continues to develop for a long time after birth! Anyhow, theses processes
> are also know in plants and maybe they are a good natural method to "make"
> new species. Juvenile (or poorly diferenciated) organs are usually very
> plastic and can adapt to different conditions. If this ability to be
> morphologically plastic is important for the effective survival of a quoted
> species, it can be kept or even "improved" by natural selection.
> I have one possible example. One of the most morphologically variable
> genus in the tribe Spathicarpeae is Spathicarpa. It is small, with poorly
> differenciated ground tissues and have usually the simplest leaf type in the
> tribe (I mean the same type we find in seedlings of almost all genera of
> the tribe). One of my hypothesis (still in test) is that Spathicarpa is a
> neotenic genus in Spathicarpeae. The same for Urospathella wurdackii
> G.S.Bunting (now currently recognized as Urospatha wurdackii (G.S.Bunting)
> Hay). It is a Urospatha that flowers with the leaves of seedlings!!!! Maybe
> this kind of leaf is useful in those savannas this species occurs. Or maybe
> it is just an accident that soon will be erased by natural selection!
> In the case of the supposed M. dubia that flowers with juvenile
> flowers, we can make some free speculation about this. In the "normal"
> environment of the species, maybe it is not a good idea flowering this way,
> because pollinators may not be able to find the flowers. Meanwhile, if this
> plant spread to new areas, maybe with smaller trees and different potential
> pollinators, it can prove to be successful (in evolutionary aspects), so it
> can diverge from the main species and become ANOTHER species. If evolution
> can be so creative than me (I don't think so), it is really possible to
> occur in nature!
>
> I hope you enjoy those crazy ideas!! :o)
>
> Eduardo.
>
> >From: "Peter Boyce"
> >Reply-To: aroid-l@mobot.org
> >To: Multiple recipients of list AROID-L
> >Subject: flowering 'juvenilies'
> >Date: Thu, 15 Jun 2000 16:45:43 -0500 (CDT)
> >
> >Dear All
> >
> >The newly raised issue of juvenile monsteroids flowering is
> >interesting because, while the production of flowers by a plant
> >vegetatively in a juvenile phase does occur in the monsteroids,
> >notably Monstera tuberculata, Rhaphidophora hayi, R. latevaginata,
> >R. pachyphylla, R. parvifolia, R. okapensis and Scindapsus lucens,
> >this 'M. dubia' thing is that the plants are flowering with very small
> >leaves and BENEATH the leaves, whereas in all of those listed
> >above while the juvenile growth morphology is retained into
> >flowering in most instances the leaves of flowering individuals are
> >considerably larger than those of youngsters and the
> >inflorescences are carried clear of the leaves either at the tips of
> >clinging shoots or on free shoots arising from the leaf axils. If the
> >description of this 'dubia' plant is correct it would appear that
> >inflorescences are arising directly from the leaf axils. Because
> >aroids ALWAYS flower at the shoot apex it would mean that in this
> >plant each inflorescence is carried at the tip of a very short shoot
> >arising in the leaf axil (the same situation as in Pothos scandens) -
> >a feature not yet recorded in the Monstereae.
> >
> >Pete
> >
> >----------------------------
> >Peter Boyce
> >Herbarium
> >Royal Botanic Gardens, Kew
> >Richmond, Surrey
> >TW9 3AE
> >Tel. (+44) (0)20 8 332 5207
> >fax. (+44) (0)20 8 332 5278
> >email: p.boyce@rbgkew.org.uk (work)
> > boyce@pothos.demon.co.uk (home)
> >
> >
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