>>Besides, the category "subspecies" is a nonsensical term anyway, >>and has
>>no place in a classification of diversity.
>Does it have something to do the fact that species from the same >genus can
>interbreed with each other? Does that make them so similar >genetically
>that further breaking down into categories of subspecies >is an inaccurate
>way to classify their relationship to each other?
Not quite. Sorry for the jargon, there's no easy way to put this...
If one is operating under the Evolutionary Species Concept (ESC), species
are lineages of ancestor-descendant populations which maintain their
identity from other such lineages and which have their own evolutionary
tendencies and historical fate (Wiley 1978). Due to the fact that species
are "individuals", rather than "classes", they cannot be defined, only
described or diagnosed. Species diagnoses are based on characters unique to
a lineage, which are termed autapomorphies.
The category "subspecies" has been used by some taxonomists (more frequently
in the past, and within certain groups [birds, herps]) as a category of
convenience to delineate populations which are unique, and diagnosable, but
which they don't "feel" warrant "species status." This is often an arbitrary
decision based on some sort of hypothesized introgression or purported
hybridization. Under the flawed Biological Species Concept (BSC), species
status is dependent on the attainment of reproductive isolation. With
allopatric species (where a larger population is subdivided by a vicariance
event, and the two populations differentiate), this is not "tested" until
the two populations are reexposed to each other. This is absurd! Since
allopatric speciation is hypothesized to be the primary means of
diversification, if you can't test species boundaries, you've got a real
problem. If they do occur in sympatry, and hybridize, then scientists
operating under the BSC would view speciation as being incomplete.
Why is this a problem? Well, if the supposedly interbreeding populations are
not sister taxa (more closely related to each other than to anything else),
then the lack of reproductive isolating mechanisms is a moot point!
Without a phylogenetic analysis to determine the relationships within
the populations/species, there's no way to identify sister taxa. The large
number of subspecies we have now are a reflection of a prior way of doing
systematics, one which is slowly being replaced as we gain data on various
groups of organisms...and as old taxonomists retire!
I hope this helps clarify the matter.
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