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Speciation challenges the meaning of "beneficial mutation"

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Speciation challenges the meaning of "beneficial mutation"

Postby wildfunguy » Sat Sep 28, 2013 11:11 pm

I was kind of crowding this thread with my thoughts on this.
post-156965.html#p156965

This rather long post is about about genetic variation and hyrbid viability, and how this gives a new perspective on speciation. I am a GED-holding college student.

The biological species concept defines species as unable to produce viable hybrids. Hybrid viability brings into question the typical notion of an allele as beneficial or harmful. The hyrbid's alleles might have been very beneficial to its parents, but the hybrid's problem is one of compatibility. The hybrid is like a car that doesn't work because it's made of both Toyota and Nissan parts. A good Toyota conforms to the Toyota blue-print, and a good Nissan conforms to the Nissan blue-print. The hybrid conforms to neither blue-print. It's a crappy Toyota, and a crappy Nissan.
When you take this perspective on speciation, you realize that reduced hyrbid viability shouldn't necessarily be proportional to genetic divergence. Genetic stability must also be taken into account. If there is a sudden surge of mutations in both populations, that is only empty variation that will be gone in no time. If hyrbid viability is low at that time, it is only because viability has been reduced across the board. What we would need to look for are mutations that are specifically A-beneficial or specifically B-beneficial, where A and B are our two populations. It is these mutations that would indicate true divergence.
Indeed, such variations could be present even before the population has been split up by a geographic barrier. Prior to a geographic split, there could have been A, B, and C variants, where only A and C variants were incompatible. While the B variants might have been favored for universal compatibility, they would lose that advantage if the A and C variants came to dominate separate regions. At that point, the disappearance of the B variants could result in speciation without the production of any new mutations.

Are there any problems with the concepts I have put forth?
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Re: Speciation challenges the meaning of "beneficial mutation"

Postby Cat » Sat Oct 05, 2013 1:47 pm

wildfunguy wrote:Are there any problems with the concepts I have put forth?


Yes. It's not "unable to produce viable hybrids", but rather "reproductively isolated". Meaning that their hybrid offspring is sterile (like mule); or that they are geographically isolated and, therefore, cannot breed in nature even if they could when brought together (you cannot possibly test all species)...
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Re: Speciation challenges the meaning of "beneficial mutation"

Postby wildfunguy » Wed Oct 09, 2013 2:46 pm

Cat wrote:
wildfunguy wrote:Are there any problems with the concepts I have put forth?


Yes. It's not "unable to produce viable hybrids", but rather "reproductively isolated". Meaning that their hybrid offspring is sterile (like mule); or that they are geographically isolated and, therefore, cannot breed in nature even if they could when brought together (you cannot possibly test all species)...

That might be what Wikipedia says, but it's not what my 2011 Campbell biology textbook says. According to the biological species concept, a species is defined by the ability to produce "viable, fertile offspring".

(you cannot possibly test all species)...
There isn't yet an agreed upon definition of species. That is just the definition of species according to the biological species concept.
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Re: Speciation challenges the meaning of "beneficial mutation"

Postby Cat » Tue Oct 15, 2013 12:00 am

wildfunguy wrote: There isn't yet an agreed upon definition of species. That is just the definition of species according to the biological species concept.


I agree. However, the stress in the definition should be on 'fertile' offspring instead of 'viable' offspring that you discuss in your original post...
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