Re: What is a Species (was Re: Iris setosa)


>I don't know beans about taxonomy but I think a species is determined by
>measuring the pollen.  Then there is some further theory that a plant with
>plentiful viable pollen can sustain itself as opposed to a plant that cannot
>produce seed easily.
>
>Someone may comment further here.  I recall reading an article on this subject
>and there are definite measurements of pollen in relation to the establishing
>of what is a hybrid.

Some confusion here.  One can often establish the tetraploid status of a
plant by measuring pollen, but not its species status.  The evidence that a
plant is representative of a different species is much more complex and
involves the physical appearance of the plant, its genetics and
biochemistry, and even its ecology.  In general, taxonomists see species as
entities that first are populations (an individual can't be a species) and
secondly that are distinct from other populations in some consistant
way--just as hookeri evidently is biochemically distinct from setosa.

Distinctiveness and difference can be two separate concepts.  We can have
distinctiveness without much difference, so long as there is always an
unbridgable gap between the populations.  On the other hand, two
populations can be wildly different from each other but still not be
distinct if they are connected by a spectrum of intermediates.

Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<bills@hsc.edu>
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