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Species Cross-breeding


Scienceman

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I have been told that many different species will cross-breed in a community tank such as Blue Dolphins / Peacocks / Proteomelas sp.

By definition the offspring from these cross-matings should be infertile. Is this the case?

Definition of a species is - two organisms that can reproduce and produce fertile offspring.

Therefore as the species mentioned above all have different genus and species names they should not be able to cross breed and produce fertile offspring.

Cheers,

Scienceman huh.gif

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Hi Scienceman,

Actually my dictionary defines ‘species’ as:

‘…group of animals or plants subordinate in classification to genus and having members that can interbreed and that differ only in minor details…’

No mention of infertility ohmy.gif

BTW ‘genus’ is defined as:

‘…group of animals or plants having common structural characteristics distinct from those of all other groups, and usually containing several species…’

Cheers,

Literatureman smile.gifsmile.gif

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HI Literatureman,

Nice challange clap.gif but...

I'm just remembering back to my high school biology. Your definition supports my point - they are capable of interbreeding. If they can interbreed they are the same species So why do we have different species names for fish such as Pecocks, Blue Dolphins etc? If these can interbreed they should be the same species????? (And we would then differientate them by race.)

I think the fertility thing is pedantic science. Eg a horse and donkey can interbreed but their offspring, a mule is not fertile and so horses and donkeys are different species even though they can do the "wild thing" together!!

There might be something I am not considering so would welcome any suggestions?

Cheers,

Scienceman

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we are talking about species issues, not breed issues (which is what you are referring to with dogs) thumb.gif

scienceman, it is well acknowledged that many of the species of malawi are extremely closely related. as such even fish from different genera can interbreed and produce "fertile" young. in the reading I have done, I am lead to believe that this rarely if ever happens in the lake. it usually happens in the aquarium, which is a man made environment. considering some of these fish can end up having a fraction of the territory they would in the wild when in an aquarium, its no surprise they get a little confused is it?

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I would also add that high school biology tends to make many rather simplified explanations of a lot of areas of science. but if you wish to refer to it you should also remember that one of the cuases for species not interbreeding is behaviour. they potentially can interbreed and produce fertile offspring, but don't due to behaviour. from memory darwin pointed this out in the finches he studied. so with the aquairum potentially changing the environment so much for fish, their behaviour can be significantly changed from the wild. that isn't something the classification system was meant to cope with was it?

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I think you have hit the nail on the head and shown were my argument went astray. I found the following reference

Huxley (1942)

"In general, it is becoming clear that we must use a combination of several criteria in defining species. Some of these are of limiting nature. For instance, infertility between groups of obviously distinct mean type is a proof that they are distinct species, although once more the converse is not true. Thus, in most cases, a group can be distinguished as a species on the basis of the following points jointly:

1. a geographical area consonant with a single origin;

2. a certain degree of constant morphological and presumedly genetic difference from related groups:

3. absence of intergradation with related groups."

"In most cases a species can thus be regarded as a geographically definable group, whose members actually interbreed or are potentially capable of interbreeding in nature, which normally in nature does not interbreed freely or with full fertility with related groups, and is distinguished from them by constant morphological differences."

"Thus we must not expect too much of the term species. In the first place, we must not expect a hard-and-fast definition, for since most evolution is a gradual process, borderline cases must occur. And in the second place, we must not expect a single or a simple basis for definition, since species arise in many different ways."

There are a lot more interesting definitions at http://sorrel.humboldt.edu/~kll1/speciesdef.html

if anybody is interested.

Thanks for the clarification and interesting discussion,

cheers,

Scienceman laugh.gif

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