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Re: [Killietalk] arnoldi story
Chris wrote:
Wright,
How does one differentiate between two closely related species.
Back when I got into the hobby (early '50s), it was really easy. If they
produced fertile offspring they were the same species. If they didn't,
they were not. Then the water started getting muddy... :-)
I don't
believe that there is any magic number of restriction fragment length
polymorphisms (RFLPs) that determines species. If there were it would
take all the fun out of taxonomy. Different species have different
numbers of RFLPs between them depending on how broad the gene pool of
that species is.
Agreed.
Some species, like ours (H. sapiens sapiens), have a very small gene
pool and all members are very closely related. Where as other species
have much broader gene pools and individuals are not as genetically
similar.
This tends to be particularly true when the reproductive isolation is
fairly recent, but wasn't always constant, historically. Look at Desert
Pupfish for a good example. Floods and varying water levels allowed all
kinds of genetic combinations at times. At other times they have gone
centuries in complete isolation.
I know you are a dog person so lets use this for instance, according to
Coppinger, et al, it is not possible to differentiate between Dog, wolf,
Coyote, and Jackal DNA. The line between species is too vague. They
share too many genes and the distribution of genes is somewhat random
among the whole group.
This is where species definition frequently becomes more a matter of law
and full-employment-for-game-wardens policy than a matter of science. :-)
Collector ego trips also make defining new species highly desirable. It
gets even worse when Brazil gives a cash award for each new species
defined. I'm not impressed when the difference between species depends
on the relative length of the 7th and 8th anal fin rays. :^) Many SA
Annuals are getting close to being that absurd.
I'm far from an expert on this so please correct me if I'm mistaken.
Actually I'm not disagreeing with your hypothesis I just don't think we
are at the point where we can say this male is not the same species as
this female when those species are very closely related.
As an expert in molecular biology and taxonomy, I'm a pretty good
electrical engineer. ;-)
I believe (without proof) that closely-related species, like FIL and ARN
tend to select mates of their own species when in the wild, but can
create somewhat fertile offspring if they are forced into the company of
a mate of the other species after collection. When that happens,
fertility may never be good, and probably drops with each new generation.
FIL and ARN females are distinguished by the points on the ARN caudal
and the rounded caudal of the FIL female. Otherwise, they might be
pretty hard to tell apart. Question is, are they kept strictly apart at
the holding site of the commercial collector? Is the collector
unscrupulous enough to send females from one site and males from another
to reduce breeder competition? Are we sharp enough to catch such subtleties?
I'm particularly suspicious of the *Paludopanchax* sub-species as they
all have shown real breeding problems after a generation or two in
captivity, and they are collected practically within walking distance of
each other, usually commercially shipped out of Lagos, Nigeria. That
part of the world is better known for bigger scams (I am getting
$25,000,000 just for letting them use my bank account), but honesty and
honorable behaviour isn't given much value in that region.
I really don't know enough genetics to know if a DNA test could be
devised to clearly distinguish these closely related (and, in the case
of *arnoldi*, highly variable) species. I don't think we will get
long-term survival in the hobby without such a test or a whole lot of luck.
I'll be interested in seeing how the KCC *arnoldi* initiative works out.
In fact, I'd like to be a part of it, if more breeders are needed.
Wright
--
Wright Huntley -- 760 872-3995 -- Rt. 001 Box K36, Bishop CA 93514
"...there are only a limited number of things that government
can do more effectively than individuals or other organizations
can do."
-- T. Sowell
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