Response to selection for increased pupa weight inTribolium castaneumas related to population structure

Abstract

SUMMARY: The effectiveness of selection for increased pupa weight inTriboliumwas compared for three different selection systems. In all three systems the same number of breeding individuals was used each generation. Population L was a large random mating population with 24 males and 48 females selected each generation. The C₄and C₈populations were each divided into 6 subpopulations (lines) consisting of 4 males and 8 fem ales. Each of the three populations was replicated. In C₄, selection for pupa weight was within lines for three generations, followed by a generation of among-line selection when the best two out of six lines were selected. These lines were then crossed to produce 6 new subpopulations, and the cycle was repeated. The C₈population was handled in exactly the same manner except that seven generations of selection within lines were practised before each generation of among-line selection. Selection response for the 42-generation period was significantly greater in the L population than in either subdivided population. No consistent differences among the selection systems were apparent when evaluating short-term response for the first 12 generations of the experiment. The results were interpreted as indicating that the influence of multiple-peak epistasis was not of major importance for this trait in determining ultimate response to selection when starting from a base population of previously unselected lines and utilizing a within- and among-line selection regime.