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SPEC-tridentata and setosa

Jumping in on this discussion after a brief pause for family activities
and visitors, I would like to comment on two points which relate to
refugia during the last ice-age. Firstly, in response to Diana's
question "Do you think that the tridentata ancestor may have been shoved
down the middle of the continent by the last glacier and had to evolve
more to adapt to the climate that developed in the south?"  This seems
an unnecessarily complicated explanation.  The glaciation lowered the
sea level considerably and the newly exposed lowlands on the east coast
would have been an idea refuge for the development of hookeri.  It would
also have provided a route south for tridentata.  There must have been a
reason that the two split into two species - was there a very large
estuary at that time where the Hudson or Chesapeake now exists? After
that separation, then the tridentata could develop character which would
be warm climate specific.

On the west coast, setosa does occur in various form in different parts
of Alaska,eg. a coastal form and an interior form.  There was a large
unglaciated refuge in the Yukon, which would explain the occurance of
this species in that region and the adjoining area of northern British
Columbia.  I might note, for Bill's interest, that the Biological Survey
of Canada has just published a 4.5lbs book on the species (I believe
largely invertebrates) of the Yukon which might be of great interest in
the analysis of refugia species.

Ian, in Ottawa where we have just had 15cm (6 inches) of snow and it is
quite mild (-5C).  Merry Christmas to everyone!

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