Re: OT: Chimera

I have found the definitions of chimera given here to be interesting.  It
puts a different perspective on the word for me.  It sort of puts sport and
chimera into the same category.  The only difference is that in a sport
there is no mixing of traits, but rather an entire branch or propagule is
different (but at some stage, in the beginning, they would have fit the
definition of a chimera, when the mutation first started, and before it
became "separate").

My understanding of the word in the past is less all inclusive, and it
always bothered me that Iris flowers with broken colors are often called
chimeras.  I've never really thought of it in the terms that Neil presented
though.

The definition I've always gone by is that a chimera incorporates genetic
material from two different individuals, not mutations from the same
individual (which I would have considered sports, or perhaps deformities).
The two sources of tissue can be fused in a number of ways.  Gametes can
fuse into one individual without combining genetic material, thus two sets
of tissue develop through the entire individual.  Fused embryos (ie. in
twin embryo seeds) can do the same.  Tissue mixing from grafting (natural
root grafting, natural stem grafting, or artificial grafting) is perhaps
best known.  There is a well known example of a Laburnum and a purple Broom
that have fused, and produce all sorts of weird combinations of foliage,
stems, growth habit, and flowers.  These two aren't even in the same genus,
so it is a very striking example.

When a plant has minor mutations or some sort of chemical trigger that
causes a color change in part of a flower, I've never heard that called a
"chimera" so far, except by Iris growers.  True this is genetic, but these
are all genes from one individual, and not a combination of different
genetics per sey.

By the definition that any mutation that causes a disparity in coloration
(or it could be morphology too), then most individuals of most species
would probably fit the definition of a chimera in one way or another (the
two eye colors is a good example, but what of people or animals that have
mismatched patches of hair or skin, or those that have an extra digit on
one appendage, but not another.  These are all usually caused by some
genetic mutation or some chemical signal that went a bit off.

By the definition I've followed all these years, no Iris flower that I've
seen so far would actually be a chimera.  Chimeras would be considered
quite rare.  Variegates usually wouldn't be considered to be chimeras
either.  However, by Neil's definition, I would suspect that many Iris
flowers are chimeras, perhaps even most with broken flower colors.

It would be interesting to hear other perspectives on this.


Dave

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