Fwd: Re: interbreeding

["Ed Pon" <edpon@hotmail.com>]

>I remember from my killie days that there are several species of 
Aphyosemion
>whose various populations and subspecies were occasionally incompatible 
as
>far as fertility, while other species in the genus were crossable with
>similar species.  Go figure.  Over time, isolated populations can 
develop
>differences in chromosome count, or differences in gene arrangement on 
the
>chromosomes.  How this happens, I don''t have a clue.  Maybe Dr. Uwe 
can
>handle the technical part of this answer.
>  It does seem reasonable therefore that between different populations 
of A.
>aggasizii, especially different color morphs from different major 
areas,
>there can be some lack of fertililty in cross-spawning.  I guess the 
best way
>to answer the question is to try it.  Please, though, if you do it, 
remember
>that purity of strains is significantly important to the majority of 
us.
>Bob Dixon
>
Some one on an earlier post mentioned that this is where the definition 
of "species" comes into play.  The definition of species has appeared to 
be a lot less clear-cut than my days in high school biology (long ago) 
when it was than members of the same species can produce fertile 
off-spring.  In recent years, I have heard that members of different 
species can conceivable produce fertile offspring but maybe not carry 
the fertility to the 2nd or 3rd generation (don't remember where I heard 
this).  Anyway--does anybody know what is the currently accepted 
definition of species?  We have been warned of cross-breeding 
Apistogramma species, yet I have never seen one.  

When Dr. Uwe Romer spoke in San Francisco, I asked him why the various 
books on apistos did not list fin-ray counts, scale counts, gill-raker 
counts, and intestinal lengths as Pierre Brichard did on his first book 
on Lake Tanganyikan cichlids.  Dr. Romer thought that there was too much 
overlap of those physical descriptions to provide very much value in 
identifying apistos.  I think the answer to some of these questions may 
be cleared up by DNA studies of the various apistos.  There are many 
cases of parallel evolution where fish that were not closely related 
appeared that they were close related--i.e. Paracyphrochromis and 
Cyphrochromis (spelling?) genus of Lake Tanganyika. So if you see two 
fish that look like Aggies, are they both aggies?

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