Re: [asa] Question on speciation

Terry wrote:

> Keith,
>
> All your examples are populational and gradualist. Not that I
> dispute them. But isn't it the case that if you compare major
> orders of mammals (even human/chimp), for example, that there seems
> to be signficant chromosome rearrangements that accounts for the
> differences. A chromosome rearrangement would be more akin to a
> single mutation, but one that might wreak havoc in producing viable
> offspring in a mating with an individual without the rearrangement.
>

Yes, I did not attempt to be anywhere near complete or
comprehensive. I should have mentioned chromosome rearrangements --
from fusions and duplications of entire chromosomes, to
translocations and other movement of chromosomal fragments.

>
> What kind of models are there for a chromosomal rearrangements
> turning into speciation events. I suppose one could imagine a
> successful interbreeding with a limited viability in the offspring,
> but as the rearranged chromosome propagated in the population that
> the chances of two individuals with the rearrangement increasing
> with time. A pairing of two individuals with the rearrangement
> would may then produce a more viable progeny and a form of
> reproductive isolation, especially if there were any phenotypic
> consequences of the rearrangement. With sibling interbreeding this
> might fix the rearrangement in a small population fairly rapidly.
>
> Alternatively, it could be suggested that chromosomal
> rearrangements are the consequences of reproductive isolation and
> perhaps the end result of a long process of speciation rather than
> the cause of it. Is there any definitive opinion in the literature?
>

  I am really out of my expertise here. I do not know the genetic
literature well enough. The biologists among us can comment.

Keith

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Received on Fri Feb 1 18:49:46 2008