[Taxacom] Polar bears as a subspecies or species

[John Noyes]

Hi Jody, 

The answer to that is not easy and straightforward, but personally I
would say yes, they are the same species. However, mammal and bird
taxonomists have a different approach to most insect taxonomists (I am
an insect taxonomist) for many reasons. In many cases, the decision has
to be made using a pragmatic approach (legal or otherwise) to accept
them or not as valid species. In the vast majority of cases, taxonomists
do not have sufficient data available using reproductive isolation as a
criterion and have to rely on morphological, molecular or biological
discontinuity.

John


Department of Entomology
Natural History Museum
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London SW7 5BD 
UK
jsn at nhm.ac.uk
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-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Jody Haynes
Sent: 22 January 2009 12:15
To: Taxacom
Subject: Re: [Taxacom] Polar bears as a subspecies or species

We must keep in mind that the manner in which hybrids are treated 
taxonomically depends in large part on the species concept being
employed by 
individual taxonomists. If you adhere to Mayer's Biological Species
Concept, 
then Steve's and Ken's points below are certainly valid. But there are 
plenty of other species concepts that do not require complete
reproductive 
isolation. Right now there are literally thousands of validly published
and 
widely recognized species -- of both animals and plants -- that have the

ability to successfully interbreed with other equally valid and
recognized 
species and produce fertile offspring. Based on the argument below,
would 
this, then, necessitate that all of these "species" should now be
considered 
"subspecies?"

Jody

----- Original Message ----- 
From: "Kenneth Kinman" <kennethkinman at webtv.net>
To: <taxacom at mailman.nhm.ku.edu>
Sent: Wednesday, January 21, 2009 9:07 PM
Subject: [Taxacom] Polar bears as a subspecies or species


> 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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