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SPEC: Variability


From: "Ian E. & Shirley Efford" <avocet.intl@sympatico.ca>

Dan raised a couple of questions about variability in versicolor and
setosa.  Firstly, the ice age eliminated virtually all life from the
northern part of Canada and parts of the US, especially the eastern
mountains, during a period which ended about 12,000 years ago.  There
were a number of protected exceptions, the Yukon area seems to have been
between two ice sheets as were the two coastlines.

Iris setosa was apparently split into two.  One forms the present
setosa, centred around Alaska and the Yukon and extending down a little
into British Columbia and probably the NWT, but I can not remember if it
actually recorded from that territory.

The other one remains hugging the east coast of Canada and New England
as Iris hookeri.

I. versicolor originated a cross between virginica and setosa
[hookeri].  It covers all of eastern Canada and extends down into along
the east coast of the US.  Tony Huber has traced virginica shrevei
coming up the Mississippi into the Great Lakes and down the Ottawa River
to the St Lawrence.  Obviously, this movement has occured after the Ice
Age. It is know from as far east as Quebec City where it just about
reaches hookeri.

As to variability on the eastern margin of versicolor's range, this may
be due to climatic or geographical variability at that end of the range
compared to the western edge, which is Saskatchewan.  It should be
noted, however, that the general history of variability in species is
that it occurs most often at the margins of the distribution areas,
rather than in the middle.  This is because the margins move back and
forth and this gives rise to isolated populations which developed
significant differences.

Finally, as Brian Mathew states, virginica and versicolor are sometimes
considered the same species as they are a devil to separate.  Sandy,
Maureen and I have about ten "stocks" between us and each on is easy to
identify.  Put them all side by side and doubts begin to arise.  I now
have a bed which is devoted to comparing these plants and defy anyone to
really separate the species.  The so-called beard on virginica is, in my
view, a result on too much whiskey before examining the material!  Black
stems for virginica - we have green, black nodes, some black stems, and
black stems,.....  What we need is a detailed doctoral study on this
complex with the best biochemical and chromosomal analysis.

I say all this, knowing that Bill Shear has a much more up to date
knowledge of the theory of evolution than I do and he is welcome to
destroy my arguments!!

Ian, in Ottawa where dandfordiae will flower tomorrow and Panayoti
Kelaidis arrives today to give two lectures.

------------------------------------------------------------------------
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