Re: [Killietalk] Commercial imports; what to label them?

[Barry Cooper <bjc3 at centurytel_net>]

John..

the difficulty that lies in your question is defining what a species is. 
Some time ago Tony Terceira recommended a book "Genes, Categories and 
Species" by Jody Hey. I bought the book and have only just begun to read 
it, but I am already finding it very interesting. It cost me only about 
$7 through Amazon.

The book addresses the "species problem", which is that nobody can 
really define what constitutes a species. The whole concept of species 
comes from our human desire to categorize things, but nature doesn't do 
that. Living organisms vary on a continuous scale. Thus, over time 
organisms will change. If they are in the same environment, able to 
freely interact, the whole group will presumably share those changes. If 
organisms are isolated, such that they can't interact, the changes that 
different groups will acquire, over time, will not be the same. Who can 
say when the differences between those groups become sufficient to 
qualify them as different species? To answer my own question, nobody 
can. It is obvious when we compare, say, dogs and pigs, that these 
organisms are different species. It is not obvious, however, that two 
groups of fish that look almost the same but that are from different 
localities, even if geographically close together, are the same species.

Taxonomists decide on certain features to use in grouping organisms into 
genera and species. What those features are are the arbitrary choice of 
the scientists, but choosing different sets of features, say bone 
structure vs scale and fin ray counts (in fish) can produce different 
results. That's why scientists sometimes disagree about what species a 
certain fish represents.

All this means that you can't be certain that two groups of fish, albeit 
similar in appearance, that are from different localities are the same 
species. In turn, that is why it is important to keep them isolated, IF 
you value the idea that you are keeping the fish as much like they were 
in nature as possible. Regarding cross breeding, the effects can be 
variable. There is such a thing as hybrid vigor, where crossing two 
inbred strains can produce stronger offspring than those produced by the 
inbred animals themselves. Unfortunately, however, crossing two strains 
that are in some way different, can produce inferior offspring, which we 
may see as poor fertility. To use an Americanism, it's a crap shoot. 
Sometimes hybridization may produce weak offspring, sometimes strong.

Some might say that we have to look at the DNA, that is at the genes. 
Sorry, but there are no genetic markers that tell us if two fish belong 
to the same species. The genetic studies that are commonly done today 
can tell us if different groups of fish are distantly or closely related 
and thus can sometimes tell us that two groups of fish (localities) are 
likely to be different species. If we see no difference in the genetic 
sequences studies, however, we cannot say with certainty that the two 
groups are the same species.

Finally, regarding longevity in captivity, some fish can survive form 
many years in the hobby with little change. N. foerschi, for example, 
survived in the hobby for decades between the original collection and 
our rediscovery of the type locality in 1997. The wild fish and the 
aquarium strain were virtually indistinguishable. There is no rule that 
says that we have to out-cross groups of aquarium fish in order to 
maintain fertility or any other attribute.

This probably confuses as much as it helps. These comments reflect my 
own understanding. Possibly some of the taxonomists amongst us will 
choose to disagree.

Barry

Barry J. Cooper
Sweet Home, OR 97386



Hladky, John wrote:
> Lee Harper wrote...
> " Or weaken it depending how closely related they were. For example, suppose a 
> breeder had a male Akure and because of necessity he had available only a wild 
> gardneri from that area labeled CI-05. ( I happen to have that fish), If he 
> mates his male and the wild female there is a reasonable chance they could be 
> infertile after one, two, three generations, if the wild fish was genetically 
> separated by geography or time from the original Akure."
>
>
> Does the new blood weaken it if it is more closely related or more distantly related?  
>
> I know mules are infertile, and I believe Ligars (lion X tiger) are too.  This after only one generation.  But these are not the same species.  Swordtails X Platies, also different species, are more closely related and remain fertile after dozens to hundreds of generations.  Thus 2 killies of the same species, and even same sub-species should be fertile forever.  Am I missing something?  Seams to me that line breeding (or in-breeding) for several generations would be a more likely culprit for infertility several generations after a collection.  
>
> If most lines of collected killies peter out after a couple generations, seams a waste of time.  This would make the establishing of an "aquarium strain" for each species (or sub-species) that could survive many generations in the aquarium even more important.  
>
> Cows are not fish, but they have been domesticated for 1000's of generations.  Angles, discus, whiteclouds, zebras, guppies, have all been domesticated for 100's of generations.  What make killies so different?  
>
> I know many of you seasoned killiekeepers are shaking your head and thinking "What an idiot!"   But as I tell my wife when she shakes her head and gives me that look, "I don't know what I don't know."  
>
> John in Huntsville
>
> PS Thanks Lee for the answer.  
>
>
> -----Original Message-----
> From: killietalk-bounces at aka_org [mailto:killietalk-bounces at aka_org] On Behalf Of LeeH920226 at aol_com
> Sent: Tuesday, July 31, 2007 11:27 AM
> To: killietalk at aka_org
> Subject: Re: [Killietalk] Commercial imports; what to label them?
>
>
> In a message dated 7/31/07 12:20:03 PM, John_Hladky at tdytsi.com writes:
>
>
>   
>> Under this scheme, new importations would help strengthen the
>> Akure line for instance. 
>>
>>     
>
> Or weaken it depending how closely related they were. For example, suppose a 
> breeder had a male Akure and because of necessity he had available only a wild 
> gardneri from that area labeled CI-05. ( I happen to have that fish), If he 
> mates his male and the wild female there is a reasonable chance they could be 
> infertile after one, two, three generations, if the wild fish was genetically 
> separated by geography or time from the original Akure.
>
>
>
> Lee Harper
> Media PA
>
>
>
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