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Re: definition of species



Stan wrote:
:I would suggest something more like "a species is
:a group of interbreeding populations that does not *effectively*
:interbreed with other such groups".
:The idea here is that any *intrinsic* factor which prevents
:the formation of hybrids (including innate behavioral factors),
:or which makes the hybrids less viable reproductively, can
:become a segregation factor.

It might be useful to point out here that, although Stan's criteria are the
accepted official "biological" criteria that are espoused by the biological
sciences, it is actually RARELY applied in naming new species, even extant
ones.  How many marine biologists have 'donned SQUBA gear and dove to the
locality of a possible new coral species, and waited...and waited...to see
if it's sexual reproduction is different from it's morphologically-nearest
named species?  How many Amazon ornithologists have captured unusual-looking, 
possibly new, birds and brought them back to the lab and have attempted to mate
them with morphologically-close relatives in order to see if they produce viable
offspring BEFORE naming them as new species? 
 The reality is that most most holotypes of new living species were either 
bonked over the head, gassed, or shot, and interbreeding tests and population
dynamics studies were ommitted (usually done long after the new species was
named, and usually by another biologist in a discipline different from 
Systematics.  I suspect (but don't have any proof, so no flames! :) that species
numbers in our modern world are probably vastly over-estimated, with 
intra-specific variability being the "smoking gun".  There are presently over 
8000 bird "species" living today.  How many of that number are actually distinct
species and how many are simply variants is anyone's guess.

  The issue of what defines a species is handled, IMHO, much more "cleanly"
and with better methodology, in, of all places, paleontology...even though
paleontology is the child of biology.  Not because
paleontologists are more scientifically-aware than biologists; it's because they
are constrained to use LIMITED morphologic characters in a more rigidly-defined
way than do zoologists, who have the luxury of naming 
living species with a plethora of eclectic character traits to pick and
choose from (and ignore, if they so desire). I have always thought that the 
genetic-interbreeding-viable-offspring part of the definition of "species"
might be better off left out.  Besides, it's generally a moot point with
paleontologists, anyway. And it's uncommonly used in the _diagnosis_ of
new living species.   Just make it a morphologically-based definition. 
It will never happen, of course, but it's an idea.  At least
paleontologists and biologists would be speaking the same language.