EFFICIENCY OF SELECTION METHODS FOR INCREASED RATIO OF PUPAL-LARVAL TO ADULT-LARVAL WEIGHT GAINS IN TRIBOLIUM

Four lines of Tribolium castaneum were selected in etch of three repli cates for increased ratio of (pupal-larval) to (adult-larval) weight g ains, using selection for increased (pupal-larval) weight gain (PL), s election for decreased (adult-larval) weight gain (AL), direct selecti on for the ratio (R) and linear selection index of larval, pupal and a dult weights (I), respectively, for four generations. Linear index was calculated with economic weights of m(2)-m(3), m(3)-m(1) and m(1)-m(2 ), respectively, with m(1), m(2) and m(3) being the means for larval, pupal and adult weights. Selection to increase the ratio Is considered to be a method to maximize the mean response in (adult-larval) weight while controlling the response in (pupal-adult) weight, and as a form of antagonistic selection to increase the weight gain during a given age period relative to the gain at another age period. Larval, pupal a nd adult weights were measured at 14, 21 and 28 days after adult emerg ence, respectively. The selected proportion was 20% in all lines. The response observed for the ratio differed significantly among lines (p < 0.01), with the I and AL lines having the greatest responses. Line R was less effective in improving the objective of selection, while lin e PL appeared to be inappropriate. The observed responses for the nume rator and denominator weight gains were positive in line PL, and negat ive in the AL, R and I lines. All lines apart from line PL decreased t he (adult-larval) weight, holding (pupal-adult) weight constant. Larva l weight showed the greatest influence on the response for the objecti ve of selection. The results for this greater than 1 ratio are compare d with results of others for smaller than 1 ratios, in which indirect selection for increased numerator is the more efficient alternative to the selection index.