Directional and stabilizing selection for developmental time and correlated response in reproductive fitness in Tribolium castaneum

Abstract

Directional and stabilizing selection for developmental time (DT) were done for seven generations in replicated lines of Tribolium castaneum. There were no significant differences between sexes or among replicates in means or coefficients of variation. For directional selection, there were significant responses in both directions, measured as deviation from control, viz. -0.35±0.15 day per generation for Fast (F) and 0.73±0.15 day for Slow (S). The unselected control (C) and the stabilizing selection (I) lines were similar, with average response per generation not significantly different from zero. - Phenotypic variation, from the first generation, was larger in the S line than in the other three lines. The I line showed a significant decrease in phenotypic variation, due mainly to a decrease in genetic variance. The realized heritability was 0.219±0.045 for F and 0.324±0.036 for S, the difference being highly significant. - Correlated response in reproductive fitness (number of pupae produced) was significant only for S (rp=-0.88 and r'G realized'=-0.79). Regression of the correlated response on DT in this line was-19.28±4.77 pupae per day (phenotypic) and -28.77±10.06 pupae per day (genetic).

Genetic correlations and reaction norms in wing pattern of the tropical butterfly Bicyclus anynana

“…Though rgs consistent with the operation of trade-offs have sometimes been found in other studies (e.g. Holloway et al, 1990; Rose & Charlesworth, 1981;Soliman, 1982), this is not always so (e.g. Stearns, 1983;Murphy eta!., 11983;Bell, 1984a,b;Holloway eta!., 1993b).…”

Selection by parasites may increase host recombination frequency

“…Numerous studies in T. castaneum show that experimental selection for almost any trait occurs within a few generations (e.g. Soliman 1982;Cardin & Minvielle 1986) while mutation can rapidly add substantial genetic variance (Enfield & Braskerud 1989). These studies are based on fewer than our 10 replicate lines, making it unlikely that our results only reflect random fluctuation (genetic drift).…”

The effect of novel environment and sex on the additive genetic variation and covariation in and between emergence body weight and development period in the cowpea weevil, Callosobruchus maculatus (Coleoptera, Bruchidae)

“…Some have successfully demonstrated the predicted genetic structure (e.g. Simmons et a!., 1980;Rose & Charlesworth, 1981;Soliman, 1982;Luckinbill et a!., 1984;MØller et a!., 1989;Holloway et a!., 1990a), but at least as many studies have not (e.g. Giesel & Zettler, 1980;Giesel et a!., 1982;Murphy et a!., 1983;Stearns, 1983;Bell, 1984a,b).…”