EFFICIENCY OF SELECTION WITH MIXED NEGATIVE ASSORTATIVE MATING AND MODIFIED TANDEM SELECTION IN TRIBOLIUM

Effectiveness of selection with mixed negative assortative mating and modified tandem selection was tested in Tribolium castaneum, using two independent experiments. In experiment 1, two lines were selected on pupal weight and adult weight in opposite directions; in the line P(+) A(-), the selected male with the highest pupal weight was mated to the selected female with the lowest adult weight and so on. Similarly, in the line P(-)A(+), the selected males with the lowest pupal weights w ere mated to the selected females with the highest adult weights, etc. In experiment 2, individual selection was carried out in two lines fo r high pupal weight (P+) or low adult weight (A(-)), and in two lines for low pupal weight P-) or high adult weight (A(+)); crosses were mad e every generation between the P+ and A(-), and the P- and A(+) select ed lines, and the F-1(P(+)A(-)) and F-1(P(-)A(+)) progenies scored. Pu pal and adult weights were measured at 21 and 28 days after adult emer gence, respectively. There were three generations of selection in each of three replicates, the proportion selected being 20%. In experiment 1, observed response for pupal weight was positive for line P(+)A(-) and negative for line P(-)A(+) (p < 0.05 and p < 0.01, respectively); the divergence between the two lines was 0.94 +/- 0.04. Adult weight c hanged significantly in the opposite direction to that of pupal weight ; the difference between the two lines for adult weight was - 0.53 +/- 0.03. In experiment 2, mean response for pupal weight was significant in both crosses (p < 0.01 and p < 0.05, respectively), positive in th e F-1(P(+)A(-)) and negative in the F-1(P(-)A(+)) cross, the divergenc e between them being 0.87 +/- 0.08. Adult weight changed in the same d irection as pupal weight in both crosses, although the mean response w as not significantly different from zero. The results of these experim ents showed that selection with mixed negative assortative mating was effective for increasing pupal weight and, simultaneously for decreasi ng adult weight, or vice versa, responses being antagonistic to the va lue of the genetic correlation between them. The use of modified tande m selection was not effective for changing weights in opposite directi ons.