In a message dated 8/18/08 6:02:41 AM, Robert writes:
> what constitutes a species? The standard version which I was taught in
> public school was that if two organisms can mate and produce fertile
> offspring,
> they are considered to be of the same species.
>
I suspect you went to school quite a while ago. If you have been keeping up
with taxonomy at all, not just in orchids, you should know that this axiom went
out the window years ago. Since the concept of species is an artificial
man-made construct, it is fuzzy at best. In most of the plants we deal with
every
day, there are well defined species, but we know now that there are many
populations of plants where the idea of species doesn't fit & the best thing we
can
call them are hybrid swarms.
Read the history of the Louisiana irises. It was the first discovery of
introgression & is quite fascinating.
There is a species of little shore sparrow, whose name I don't know, that
lives up and down the US Atlantic coast. There are several populations along
the
coast, & they look pretty much alike, but one population is just a little
different from the next. Each population will interbreed freely with the next
one.
However, if you take one sparrow from the northernmost population, it can't
breed at all with one from the southernmost population. Yet they are all one
species. This phenomenon is called a cline, I believe.
Iris
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