[Taxacom] Polar bears as a subspecies or species

Kenneth Kinman kennethkinman at webtv.net
Wed Jan 21 20:07:09 CST 2009


Steve Manning wrote:                
     Which, when and if it happens, would emphatically justify combining
grizzlies and polar bears into one species!  (Sorry, polar bears, you
might have to get with the program!  But maybe a better ending than true
extinction.) *****************************************************
Hi Steve,
      Well, maybe yes and maybe no.  It really depends on the
"evolutionary health" of such half-breeds (are they intergrades or true
hybrids).  If they freely interbreed with members of the parental
species and produce fertile offspring, then that is evidence that they
are merely intergrades between what are actually subspecies of a single
species.  However, if there are fertility problems with such
half-breeds, then that is evidence that speciation has most likely
occurred and reproductive isolation is pretty firmly established.                                  
       The fact that we have confirmed two or more such half-breeds does
not really answer this important question of the fertility of such
individuals.  If they have fertility problems, it would only accelerate
the extinction of the polar bear species.  If they don't, the polar bear
"subspecies" would still most likely suffer a slow decline in an
environment that reduces the advantages that they once had over their
brown bear relatives.  Either way, pure-bred polar bears (species or
subspecies) are in for very tough times as the ice continues to recede.
          ---------Ken Kinman





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