Q: A question: What are the criteria for deciding if two animals are the
same species, separate species or sub-species? Can you clarify this
for us?
A: And risk being blacklisted by the other magicians for spilling the
secret to the trick? Hocus-pocus, alamazoo! Poof! It's a separate
species!
The idea of species should be a simple concept, after all, everyone can
recognize that a ferret is a ferret, a cat is a cat, and a dog is a dog.
Recognizing that cats, dogs, and ferrets are separate species has a Duh
Factor of 9, but that isn't the problem. The problem isn't figuring out
the relationships of distant cousins (unless you live in certain unnamed
parts of the USA), but in the relationships of close family relatives.
When are red wolves gray wolves, European elk moose, or European red deer
elk? Or, in our situation, when are black-footed ferrets polecats, or
all polecats one?
There are several species concepts in use (biological, nominalist,
evolutionary, phylogenetic, recognition, etc.) and they all have their
particular strengths and problems. Of all of them, the most widely
accepted is the biological species concept, championed by that hotdog
of the biological sciences, Ernst Mayr (Oh, I wish I were an Ernst Mayr
party liner, that is what I truly want to be, cause if I were an Ernst
Mayr party liner, everyone would define species like me!). A species
defined under this concept is a natural population of successfully
interbreeding individuals that are genetically isolated from other
similar populations because of physiological, geographic, or behavioral
separation. In this concept, regional groups within the natural
population that have substantial differences when compared to the main
population- -but that do not remain genetically isolated- -are considered
subspecies. This distinction is often quite arbitrary. In any case,
part of the problem of subspecies is moot: there are NO currently
recognized subspecies of the European polecat. None.
Domestic species, such as the ferret, are not governed by the biological
species concept (this is why there have been so many problems with how
ferrets are named scientifically). Besides the fact that they are under
human selection so by definition are not a natural population, drop a
dozen ferrets into an area populated with polecats and the ferrets
(assuming they can survive) make zero attempt to remain reproductively
isolated. Domestic species are not the only types of species the
biological concept has problems with; asexual species, because they do
not reproduce sexually, do not fit into the concept. It doesn't take a
rodent scientist to know domesticated and asexual species are real, but
they are not recognized (except superficially) by the biological species
concept and even Ernie Mayr can't deny the problems.
Defining "isolation" is another problem. Genetic isolation means one
group will not make genetic contributions to another group, even if they
can breed and produce offspring. You see this with horses and donkeys;
they breed, make mules, but the mules are sterile and the two groups
are genetically isolated (Frances must have inherited his speaking
ability from Ed). In contrast, there are species that range over a wide
geographic area where the individuals on the west coast cannot breed
successfully with individuals on the east coast, but because they can
breed with the neighboring groups and thus maintain genetic contact, they
are not considered genetically isolated. Some of these animals have more
karyotype differences that the polecats. Where the isolation concept
starts to fall apart is when one group is isolated for a period of time,
then come back together and breed like teens on beer. At what point is
isolation, well, isolation?
For example, for some millions of years now the planet has undergone a
series of glacial periods interwoven with warm periods. Between the warm
and cold periods there is time when species from the Old World can mix
with species from the New World. That is why North American elk and
European red deer are the same species, wolves are everywhere, and the
horse was able to escape North America so the Khan could invigorate
things in the Old World. It is also why North America has black-footed
ferrets: they were steppe polecats that snuck over to snack on our
bountiful prairie dogs. That was probably at least two glacial periods
ago because remains of both steppe polecats and BBFs were found from the
last interglacial, meaning they were both here at the same time. Now,
considering the lack of restraint of male polecats in heat and what they
will do to my shoes, there is not a chance in Hades that you can convince
me that successful interbreeding didn't take place.
Under the biological species concept, this would make the BBF a
subspecies of the steppe polecat. How do I know? Because it is true of
wolves, caribou/reindeer, elk/red deer, moose/elk, sea otters, wolverine,
grizzly bears/brown bears, short-tailed weasels/ermine, and literally
scores of other mammalian species, not counting hundreds of avian
species. Get the picture? Perhaps the foremost expert on the history
of the BBF would be Elaine Anderson, who said (with other experts) about
20 years ago the BBF was a subspecies. So why is it still a distinct
species and not a subspecies? Ah, now THAT is the question!
Besides the fact that BBFs were so rare you couldn't study them, there
is no rule forcing the change, that's why. Changes are done when a
scientist decides to do a revision at some basic taxonomic level. There
are no computer alerts flashing red when the time has arrived; it is
usually done after a few experts bitch and moan, get drunk, and in an
alcoholic haze decide they are the best ones to do it. In a revision,
all the old stuff is compared with new information, and the revisionists
describe what they think are the new proper relationships. Once
published and reviewed by other experts in the field, they become the new
paradigm and await future revision from other drunken upstarts wanting to
build a reputation. And thus science shows you don't have to be sober,
you just have to be self-correcting. It is sort of like natural
selection, only the best ideas survive at least in the long run.
A revision of Mustela is overdue, but why do it now, while the best data
is just being generated? Close-up looks at the genome of the Mustelidae,
including many members of the genus Mustela, are being done in the USA,
Japan, Britain, France, Russia, and other countries. These studies are
only now showing up in publications and it is obvious within the next
decade there will be numerous others. Any revision of Mustela done
before these studies are done could be a waste of time.
Personally, I think the biological concept of species is either due for
an overhaul, or it is time for a paradigm shift. I think geological
time, evolution, and domestic and asexual species HAS to be incorporated
into the concept, and the biological species concept ignores all, seeing
selected species at a single point in time. For example, ALL species
evolve (except extinct species), yet conservation biologists are obsessed
with maintaining a genetic status quo in species, which precludes any
chance of evolving. Something to think about--extinction through
conservation.
As for our beloved polecats and ferrets, I have little doubt in my mind
that BBFs are a subspecies of the steppe polecat. I am not exactly sure
if European and steppe polecats are the same species, but I am sure in
the next decade those relationships will be genetically determined. As
for the domesticated ferret, I think I would be a fool to pontificate
that it was domesticated from ANY polecat, much less any regional variety
of polecat. I think the domestication was over a large geographic
region, included contributions from both polecats, and since the genetic
of polecats is so similar, it will be extremely difficult (or damn lucky)
for a domestication origin point to be deduced from the morphology or
genetics.
Bob C
Communications? [log in to unmask]
Questions? [log in to unmask]
[Posted in FML issue 4570]
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