Locality data

Hannon othonna@gmail.com
Tue, 30 Oct 2012 17:06:28 PDT
Jim McKenney wrote:

"*Where does geography fit into this? Breeding populations typically have a
discrete geographical range*."

This is a gross oversimplification. Modern population genetics tells us
that *what is a population* is a difficult question at best. Often a
"population" is not discrete at all (except in toto) as it may be broken up
into subpopulations by breeding barriers, geography, etc., and even these
are not always discrete. This barely scratches the surface of what little
we know about organisms and their biological and ecological systems.

"*In areas where only one species of a genus occurs, if you know the
geographic source of the entity, you know the specific identity*."

Again, a highly misleading statement because it precludes new discoveries,
including finding a species in an area where only another congener was
known previously. This is presumptive rather than scientific. These things
change constantly as field work progresses. A good example is a plant
"known only from the type locality" (a frequent refrain in the botanical
literature) that may in fact be found in another place by a sharp-eyed
collector.

"*In areas where sympatric species occur (i.e. multiple related species in
the same area) then you have to resort to traditional morphological
distinctions for purposes of identification*."

How does this differ from the use of such characters to identify allopatric
species?


Dylan Hannon




On 30 October 2012 15:39, Jim McKenney <jamesamckenney@verizon.net> wrote:

> Leo wrote: " I have been led to believe we name species based on
> differences in plant structures,not geography."
>
> What Leo wrote is certainly an accurate description of the way things have
> been done in taxonomy for centuries.
>
> However, once genetics emerged as a science, the time honored  primacy of
> morphology (structures) was challenged by a radically different concept,
> the concept of the gene pool. What the gene pool concept asserts is that
> species, at least in theory, are determined by the limits of their breeding
> population (gene pool), not by their appearance (i.e. structures,
> morphology).
>
> >From my point of view, contemporary DNA studies are fairly viewed as a
>  minutely granular version of morphology ( maybe better thought of as
> "meta-morphology"). And from that point of view, DNA studies are no better
> suited for determining species limits than traditional gross morphological
> studies.  Why? Because morphological studies, no matter how detailed, do
> not address or answer the questions which determine the boundaries of the
> breeding population. To be sure, morphological studies can accurately
> determine when two entities are NOT the same species, but morphology in and
> of itself cannot determine when two entities ARE of the same species
> (although morphology/DNA studies can provide highly probable guesses).
>
> Where does geography fit into this? Breeding populations typically have a
> discrete geographical range. In areas where only one species of a genus
> occurs, if you know the geographic source of the entity, you know the
> specific identity. In areas where sympatric species occur (i.e. multiple
> related species in the same area) then you have to resort to traditional
> morphological distinctions for purposes of identification.
>
> Jim McKenney
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