I also have a serious problem with the Warbler link you post. Just in line 2 it reads "In central Siberia, two distinct forms of greenish warbler coexist without interbreeding, and therefore these forms can be considered distinct species."
By that logic, if a group of humans go live on some Island and don't interbreed with others in the rest of the world then they are a distinct species?
So pre Columbus, humans living in The Americas were a different species to those in the rest of the "known" world?
This doesn't follow, those in the America's were
not coexisting with the 'known' world.
I agree that it is somewhat arbitrary to consider 2 coexisting populations which simply 'choose' not to interbreed as distinct species but it is a perfectly common definition under the Biological Species Concept (BSC).
There has always been a spectrum of definitions for species encompassing highly stringent definitions, relying on post-mating reproductive isolation such as genetic incompatibility, through gross morphological barriers to mating all the way to behavioural pre-mating barriers as in the Greenish Warbler example.
In the same way if there were behavioural traits which lead to there being no interbreeding between 2 populations of humans on an island then under the BSC they
would be considered distinct species.
I can't take any article that makes these "distinctions" seriously.
That would mean you basically don't take any modern population genetics or behaviorally based studies of speciation seriously, nothing in fact not based on the most stringent criteria for defining species.
If it was so simple, everyone on the planet would grasp is like 2+2=4 and no one would ever question it. The fact it can't be grasped as easily means it's not simple.
Have you never heard of the Flat Earth Society?
TTFN,
WK
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