Evolution__3rd_Edition

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Figure 9.11
(a) The main veins in the wing
of Drosophila. The relative
length of the fourth vein was
measured by the ratio L 4 : L 3 .
(b) Artificial selection for
relative length of the fourth
vein. The series on the left is for
nine generations in females,
with 10 generations of males
on the right. Each graph has,
as a green line, a frequency
distribution for the selected
population. In both males and
females, a bimodal distribution
appears at vein lengths of about
60–80. The black lines are
controls. Redrawn, by
permission of the publisher,
from Scharloo (1987). © 1987
Springer-Verlag.
(a)
L 3
(b) Females Males
L 4
0
1
2
3
4
5
6
7
8
L 5
9 10
0 50 100 0 50 100
0
1
2
3
4
5
6
7
8
9