A population of warblers is monitored for several years and

A population of warblers is monitored for several years, and the following census counts are taken: 2000: 400 2001: 20 2002: 250 2003: 400 2004: 600 What is the arithmetic mean of the census count? What is the effective population size?

In how many generations is a new allele expected to fix in this population, given this amount of year to year variability?

2. A population of warblers is monitored for several years, and the following census counts are taken: 2000: 400 2001: 20 2002: 250 2003: 400 2004: 600 What is the arithmetic mean of the census count? What is the effective population size? In how many generations is a new allele expected to fix in this population, given this amount of year to year variability?

Solution

Arithmetic mean of the census count: from year 2000 to 2004

n=5;

A=(400+20+250+400+600)/5=334

The arithmetic mean is 334.

when population size varies over time, as in the case here, the effective population(Ne) size is given by harmonic mean.

1/Ne =(1/400+1/20+1/250+1/400+1/600)/5

      = (0.0025+0.05+0.004+0.0025+0.0017)/5

      =0.0607/5

      =0.01214

therefore, Ne =1/0.01214=82.37

The effective population size is 82.37

It takes 4Ne generations to fix a new mutation/allele.

Therefore, it would take 4x82.37= 329.48 ~ 330 generations to fix the new allele