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Inbreeding


Nhewyt
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I thought this would make for an interesting discussion which could benefit old and new hands to the roach hobby alike.

Are there problems associated with inbreeding of roaches?

Are all of the various colonies of roaches in the USA related?

Are there really any colonies which are from unrelated original imports?

How many generations need to pass before there is enough genetic dis-similarity to say that any two colonies are no longer closely related?

How much genetic dis-similarity is actually possible in a roach?

Does any of this even matter?

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There are a few books and several articles and papers that cover this that are good reading. I would be interested to know what Orin knows and Blattaman too. This is what I have gleaned:

*Are there problems associated with inbreeding of roaches?

No.

*Are all of the various colonies of roaches in the USA related?

Yes and No, depending on which species you are talking about. For the most part they are.

*Are there really any colonies which are from unrelated original imports?

Yes. Again it depends on which species you refer to. Some colonies have been brought in by different universities, and there are some which have arrived originally without a permit...

*How many generations need to pass before there is enough genetic dis-similarity to say that any two colonies are no longer closely related?

So many that it cannot be known at this time. There are a number of factors which influence this, for example behavioural changes that are related to molt regulation (Richter, K. and D. Barwolf. 1994), and the article that will answer all of these questions (in a way) (Philippe, H. and A. Adoutte. 1996. Phylogentetic patterns/evolutionary processes generating biodiversity. In Aspects of the Genesis and Maintenance of Biological Diversity. M.E. Hochberg, J. Clobert, and R.Barbault, editors. Oxford University Press 41-59.)- just to name a couple of references.

*How much genetic dis-similarity is actually possible in a roach?

(please define what you mean by 'dis-similarity', which will vary by species) If you mean as in G.portentosa, where one colony may have been line bred for a color pattern and another colony has not where by you have a pool of a sort-of isolated gene (i.e. G.portentosa black vs. G.portentosa chestnut color)....that is one thing. But you can take another species like Diploptera punctata and no matter what you do they almost appear to remain looking like clones of one another.

*Does any of this even matter?

No. If properly cared for I would think a single colony would be stable far longer than you would be alive.

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There are a few books and several articles and papers that cover this that are good reading. I would be interested to know what Orin knows and Blattaman too. This is what I have gleaned:

*Are there problems associated with inbreeding of roaches?

No.

But what of the fact that in many colonies of g.portentosa after a number of generations a reduction in the size can be observed, mostly with the males? Is this simply an artifact of the colony becoming crowded (as we all know an improperly culled portentosa colony will get out of control fast), is it due to genetics and the males maturing sooner and smaller (as I read here)?

*Are all of the various colonies of roaches in the USA related?

Yes and No, depending on which species you are talking about. For the most part they are.

Agreed - though I would think that some of the species (like the common g.portentosa), although still related, have been in separate colonies long enough - and in some cases being selected for specific traits by their keepers long enough - that they are rather 'dis-similar' in size/coloration even while remaining mostly alike in all other genes.

*Are there really any colonies which are from unrelated original imports?

Yes. Again it depends on which species you refer to. Some colonies have been brought in by different universities, and there are some which have arrived originally without a permit...

Considering how tight things are with security now, I doubt this will happen again in the future. Heck, I'm sure it's nearly impossible to import them legally at this point as well.

*How many generations need to pass before there is enough genetic dis-similarity to say that any two colonies are no longer closely related?

So many that it cannot be known at this time. There are a number of factors which influence this, for example behavioural changes that are related to molt regulation (Richter, K. and D. Barwolf. 1994), and the article that will answer all of these questions (in a way) (Philippe, H. and A. Adoutte. 1996. Phylogentetic patterns/evolutionary processes generating biodiversity. In Aspects of the Genesis and Maintenance of Biological Diversity. M.E. Hochberg, J. Clobert, and R.Barbault, editors. Oxford University Press 41-59.)- just to name a couple of references.

Agreed.

*How much genetic dis-similarity is actually possible in a roach?

(please define what you mean by 'dis-similarity'.

Actually, to clarify, I would have to say there would be two areas of dis-similarity that I wonder about.

First, the cosmetics - color, size, horns and the possible major shifts in any of these three that are truly genetic and not caused by care or food source.

Second, the really 'radical' issues - change in genital structure, changes to food requirements due to actual changes in the structure and processing power of the gut, development or loss of wings, etc. etc.

*Does any of this even matter?

No. If properly cared for I would think a single colony would be stable far longer than you would be alive.

Again - agreed ;)
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