Re: flowering 'juvenilies'

From: "Eduardo Goncalves" edggon at hotmail.com> on 2000.06.21 at 01:59:48(4867) Dear Jody, Thanks for your comments. In my post, I just forgot to include a good definition of both terms. You did it with precision! I hope someone have other possible examples with other groups in this marvelous family. Best wishes, Eduardo. +More >From: Jody Haynes >Reply-To: aroid-l@mobot.org >To: Multiple recipients of list AROID-L >Subject: Re: flowering 'juvenilies' >Date: Fri, 16 Jun 2000 19:49:38 -0500 (CDT) > >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 >-- >Jody Haynes >Corresponding Secretary, Editor & Webmaster >Palm & Cycad Societies of Florida (PACSOF) > Virtual Palm & Cycad Encyclopedias > Website: > & >Seedbank Facilitator, Webmaster & List Owner >Azafady Madagascar Seedbank > Website: > E-mail List: > >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) > > > > > > > > > ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com

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