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hardy  Aroids)" <ARISAEMA-L at NIC.SURFNET.NL> Aroids)" <ARISAEMA-L at NIC.SURFNET.NL>
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From: "J.E. Shields" <jshields104 at INSIGHTBB.COM>
Subject: Re: More on conservation, and associated matters, hybridiza=
tion,  genomes, etc
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Adam and all,

Many plant species are self-incompatible, presumably to prevent excessive
inbreeding and possible weakening by accumulation of deleterious recessiv=e
gene alleles.  As I understand most definitions of "species" they refer t=o
populations which can interbreed freely.  Disclaimer: I was trained as a
chemist and biochemist; my knowledge of genetics, plant breeding, or
taxonomy, is only that of an earnest amateur.

Self Incompatibility occurs in many species of the Amaryllidaceae as well
as in other plant families.  It takes a number of forms at the biochemica=l
level, always involving something that blocks the fertilization of an ovu=le
by the incompatible pollen.

-From the MOBOT database, it appears that A. amurense is tetraploid while
A. triphyllum is diploid.  That is not surprising; speciation by polyploi=dy
is not unknown in the plant world.

Glossary:

I don't want to insult those who already know the technical terms I use,
but maybe not everyone does.

allele -- one of a number of forms of a given gene
speciation -- formation of new species from an old species

At 11:32 PM 3/9/02 -0600, you wrote:
>I see that I have touched on some sore points.  Let me tell you some of
>these points ae sore with me too!  ABout 30-35 years ago I was instrumen=tal
>in importing rare oncocyclus iris species that had not been in the count=ry
>for more than 25 years.  They were distributed among those who knew best=how
>to grow them., and those who were willing to pay in an enthusiast group =not
>unlike this  onbe but I don';t really now anyone here.  I assume that al=l of
>you who have rare species know how to grow them and never lose them
>?  )<G>?  At any rate. Many of these were hybridized.  They do not self
>readily, at all.  (Most plants have barriers to self-pollination)  And m=ost
>of what we are pleased to call "species"  are artificial entities
>established by people (not given by God, or something)  based on holotyp=es
>which are dried specimens in  an herbarium   (which in the case of irise=s
>may not exist any more, neither the herbarium or the holotype).  Some of
>these irises exist (as far as is known) only in their hybrids,
>unfortunately.,because their original provenance has been over-collected=and
>the limited colonies are gone.  Others exist in profusion, but some form=s
>are gone., others, as I noted are subject to the inroads of increased
>building, etc.
>
>I do not necessarily recommend hybridization as a primary way of maintai=ning
>any species--but, do these things self-pollinate?  and set viable seed? =So
>far the hints I've gotten are that they may, or may not.   How does a
>species maintain its identity and euploid genome and supposed uniqueness=,
>if it cannot set seed from self-pollination?  I don't have a good answer=to
>this, and suspect I won't because our conceptualization of what goes on
>isn't a sufficient tool to answer this. .  Irises set seed within coloni=es
>of a species, where (one may assume) the individuals are sufficiently
>distinct and different enough to not trigger the enzymes that would bloc=k
>fertilization, and certainly there is variation within a speciecs.  But,
>people decide  whether the variation within the colony is so great as to
>remove it from a species classification, and assign it a forma, or a var.
>or,  an aff.  or   remove it from the species, or even  the genus,.  Thi=s is
>what keeps taxonomists busy, but I'm not going to say that what's good f=or
>taxonomists (or General Motors) is good   for conservation or the world..
>
>Just in my lifetime, a number of species have become extinct. I note thi=s,
>even as I shall become extinct, and even as some of my children have.  R=e
>hybridization:I don't think I suggested that indiscriminate hybridizatio=n
>was a goal or a likelihood.  With the chromosome numbers noted so far, I
>suspect that hybridization may be more dificult than  imagined
>
>Do we even have agreement on how to grow these things?   Do members of t=his
>group grow them reliably?  year in and year out?  I salute the idea of t=he
>exchange program and the entering requirement for AEG of who has what an=d
>where .    Has each of you made arrangements about what should be done w=ith
>your collection in case of your death?    Just this last few weeks I was
>lucky enough to brng a few rare hybrids from Australia into the US.  Som=e no
>longer existed in the U.S., others were developed in Australia and never
>entered commerce here.   At this time there is one rhizome of each of
>hybrid  of a "species" for which the provenance has never been establish=ed
>
>   I should note , also, that the hybridization of oncocyclus and regeli=a
>irises has been in large measure the result of backyard gardeners who ha=ve
>taken the trouble to learn the requisite skills to raise the seed
>(notoriously difficult to germinate in the past, short of embryo culturi=ng
>it).  Very few people in the U.S. have been able to keep the oncocyclus
>species alive for more than a few years at a time  I suspect that some o=f
>the arisaemas may prove equally fractious,  but I hope not.
>
>I don't know how to grow these things in Chicago, yet., except for
>triphyllum and dracontium which are native in the area.  But I hope to
>learn.    In evolutionary terms, I would not be surprised to find that A.
>triphyllum and amurense are exceedingly close, even as skunk cabbage her=e
>and in Siberia probably are.  Thanks to all who decided to respond.  I
>printed out the information on registration of cultivars which was new t=o
>me.
>
>  Adam Fikso,  3620 Glenview Rd., Glenview, IL 60025 USDA  Zone 5a,  to =-25F

*************************************************
Jim Shields             USDA Zone 5             Shields Gardens, Ltd.
P.O. Box 92              WWW:    http://www.shieldsgardens.com/
Westfield, Indiana 46074, USA                   Tel. +1-317-896-3925