Effective population size (Ne)

[Bio-student]

Hi guys,
Got a semester exam on Population Genetics coming up in a few weeks and I'm really struggling to get my head around this concept.

I've read a number of internet sources but am still not completely certain of what it is. Could anyone give me a basic overview, also I've got it written in my notes that "genetic linkage reduces the Ne because of hitch-hiking", I understand what linkage and hitch-hiking are but not sure how this relates to Ne? I know it has something to do with genetic drift.

Thanks in advance!

 

[SW VandeCarr]

I've got it written in my notes that "genetic linkage reduces the Ne because of hitch-hiking", I understand what linkage and hitch-hiking are but not sure how this relates to Ne? I know it has something to do with genetic drift.

Thanks in advance!

'Ne' is the effective population size needed to maintain population diversity. To the extent that genetic linkage reduces population diversity, it increases the effective population size needed to preserve diversity.

http://www.ncbi.nlm.nih.gov/pubmed/20122296

 

[SW VandeCarr]

I agree, internet sources seem to be a bit confusing regarding strict relationships between the Ne and actual population diversity. My view is that genetic linkages between selective traits or between a selective trait and a non-selective (but non-deleterious) trait would favor one genotype over others and therefore would tend to reduce population diversity. Genetic drift (by definition, involving non-selective traits), however would tend to increase population diversity.

Bottlenecks, where one genotype is selected, may be followed by periods of genetic drift and/or mixing with other genotypes increasing diversity over time. Because of this, the Ne may remain small in diverse populations.