Ne
= 4NmNf / (Nf
+ Nm)
Check: if the numbers of males and females are
equal, Nm
= Nf
= N / 2, and from the formula Ne = (4)(N/2)(N/2) / (N/2 + N/2) = (4)(N2/4)
/ N = N
Where the
sex ratio of breeding
individuals is unequal, this departs rapidly
from expectation. In the extreme case with one
breeding male, where Nm
= 1, Ne = 4NmNf / (Nf
+ Nm) = (4)(1)(Nf)/ (Nf
+ 1) so if Nf
>> 1 then Ne
= 4Nf /
(Nf
) = 4. The
same is true if Nf
= 1.
HOMEWORK:
Use the Excel spreadsheet to calculate Ne
for various scenarios of Nm
&
Nf
as instructed.