Expert: John Locke - 3/8/2009

Question
Hello,

I am completely stumped on this question.  After researching each of the choices, It seems to me that none of the choices are false.

Which of the following statements about population bottlenecks is false?

1.  They can result in the loss of genetic variation.
(if I had to pick one I was thinking this one,however I am not confident becuase I think all choices are true)

2.  They arise from severe reductions in population size.
(this is definitely true)

3.  They are an extreme example of genetic drift.
(They are the first example of genetic drift in my text book)

4.  They can result in changes in allele frequencies.
(true)

5.  All of these

I think maybe the last choice should be none of these.

I'm stuck.  Can you guide me?

Answer
Thanks for using AllExperts. After considering the choices and doing some research of my own, I am unconvinced that any of these choices are false as written.

The first choice is certainly true; since genetic drift works more quickly on smaller populations, a population bottleneck can cause more drift in a short period of time and potentially decrease genetic variation. Drift is random, obviously, so it could just as easily increase genetic variation--but as the answer is written, this choice is correct; population bottlenecks have the potential to reduce genetic variation.

The second choice is part of the definition of a population bottleneck.

The third choice is perhaps the most likely candidate in my view to be the "correct" answer; a hypertechnical definition would state that genetic drift is enhanced by population bottlenecking, although the two are not synonymous. However, I don't think that this argument is conclusive, because various references I've found also describe the bottleneck effect as a subset of genetic drift. As you noted, your text does this. A specific example of such language can be found here:
http://www.talkorigins.org/faqs/genetic-drift.html
As such, I don't think that this answer is false.

The fourth choice is certainly true, for the same reasons as the first choice.

That was what I've been able to determine. I hope that this helps, and good luck.