The relationship between fitness and response to selection in Drosophila melanogaster.

The relationship between the selection response exhibited by a morphological trait and the correlated response observed on fitness values has been investigated to improve our understanding of micro-and macro-evolutionary processes. The research was designed to test the validity of the "homeostatic" and "metric deviation" models (Robertson 1956). The results show that: 1) correlated changes in fertility values are larger when selection for minus-variant wing length is applied to males than when it is performed on females, 2) within each of the selected lines, M, F and MF, the reproductive fitness of the populations obtained from vg/vg x +/vg crosses differs from that of the populations derived from +/vg X vg/vg crosses, 3) reproductive fitness values of populations derived from vg/vg X +/vg crosses are fairly constant in selected lines obtained by means of different selective procedures, while mean wing length changes; the corresponding populations from +/vg X vg/vg crosses show, on the contrary, a proportionality between fitness and selected trait values.