We used Drosophila melanogaster to test for compensatory
control of cell area and cell number in
the regulation of total wing area. In two random bred wild-type base stocks
collected from
different geographic locations we found a negative association between the
area and the number of
cells in the wing blade. Three replicate lines were selected for increased
or decreased wing area,
with cell area maintained at the same level as in the three controls. After
eight generations of
selection, despite a large and highly significant difference in wing area
between the large, control
and small selection lines, cell area did not differ significantly between
them. Rather, the difference
in wing area between selection regimes was attributable to differences in
cell number. Over the
course of selection, the initially significant negative correlation between
cell area and cell number
in the wing increased, providing evidence for compensatory regulation of
cell area and cell
number. As a result of the increasingly negative association between
the two traits, the variance in
wing area declined as selection proceeded. It will be important to
discover the mechanisms
underlying the compensatory regulation of cell area and cell number.
RAPID LABORATORY EVOLUTION OF ADULT WING AREA IN DROSOPHILA MELANOGASTER IN RESPONSE TO HUMIDITY
