So, over quarantine I decided to start
breeding Eastern Hercules beetles, and I
decided to see how long I could breed
them to be. Now my original population
has a mean length of 50 millimeters and
a standard deviation of 10/3s
millimeters, and I'm gonna be breeding
the top 10% of my population and I can
find a standardized selection point (Z) and
the selection intensity (I) on a chart and
these are given values, given
to us for the sake of calculation. Now, I
have to calculate the truncation point (x̅∨T)
any beetle above this number in length
is going to be bred together. Truncation (x̅∨T) point is the average mean, the
average length, of the original
population plus the standardized
selection point (Z) times standard deviation (σ),
and adding that together it gives me
54.273. Any beetle above that length
is going to be bred together. I then need
to find a selection differential (S). Easy.
Selection intensity (I) time standard
deviation (σ). 5.85 millimeters.
I then take this selection
differential (S) and add it to my original
mean in length (x̅∨0) and I get the selected
population (x̅∨S) of the original population,
and that's going to be 55.85. This is the mean of all the
beetles past the truncation point. I then
need to find the response to selection (R)
and this is easy to find. The narrow
sense (h^2) times the selection differential (S)
gives me the response to selection (R) of
3.9195 millimeters
and I simply add this to the
original population (x̅∨0) to find the mean of
the child population (x̅∨1) which would end up being 53.9195 millimeters,
and as you can see the
original population right here, with the
second population right here, and you'll
notice that this isn't a standard
deviation. There comes a point where a
trait
can't quite be pushed any further. See, it
might not be feasible for a beetle to
get any longer than 60 millimeters. In
this case, in the case of the Eastern
Hercules beetle, it's kind of pushing it
here.
They might not be able to survive and
molt from larvae into beetles so, at some
point, you're not gonna be able to push
past this wall. Right now I'm pushing up
against it, but eventually it's just not
gonna be able to be pushed any further,
and the beetles will stay the same
length from generation to generation.
