Experimental comparison of methods for simultaneous selection of two correlated traits in Tribolium. 2. Index selection and independent culling levels : a replicated single generation test

Abstract

SummaryIndex selection (I) was compared with independent culling levels (N) in ten replicates of a single generation selection experiment. Two correlated traits, egg laying between 7 and 11 days after adult emergence and adult weight at 12 days, were selected in Tribolium castaneum. Selection criteria included family means for egg laying and individual phenotypic values for adult weight. The response to index selection was greater than the response to independent culling levels for the aggregate genotype (8.80, 4.38) and the difference was highly significant (P < .001). The predicted response to independent culling levels was slightly less than that for index selection for the aggregate genotype. The very large difference found in the index line relative to culling level line could be due to the fact that family selection was used for egg laying. Responses obtained for both individual traits were also greater in the selection index line, and the difference was significant (P < .001) for egg laying (8.13, 3.96) but not for adult weight (0.67, 0.42). A greater response would be expected in the selection index line for each individual trait when optimum culling proportions are used in the culling levels line. Independent culling levels should be considered in practice as a relatively simple but inefficient selection method to improve egg laying and adult weight.

Constraints on the evolution of function‐valued traits: a study of growth in Tribolium castaneum

“…We explored potential constraints on the evolution of growth curves using the flour beetle Tribolium castaneum , a common insect model for population genetic and development studies. Previous work on Tribolium is bountiful, and quantitative genetic studies have shown significant heritability in body mass at the larval (Okada & Hardin, ), pupal (Conner & Via, ; Wade et al ., ) and adult (Okada & Hardin, ; Campo & Rodriguez, ) stages of development. In addition to these and other heritability estimates, the value of T. castaneum as a model system has been enhanced by publication of its genome ( Tribolium Gene Sequencing Consortium, Richards et al ., ), providing the possibility of GWAS searches or other QTL work regarding molecular control of larval growth and body size.…”

Gametic models for multitrait selection schemes to study variance of response and drift under adverse genetic correlations

“…In many cases, however, the theoretical advantages of index selection over other alternatives, i.e., independent culling, are found to be sufficiently small that these methods can be considered similar in expected gain (Young 1961;Finney 1962;Bennett and Swiger 1980;Villanueva and Kennedy 1993). Some support is also available from experiments (Sen and Robertson 1964;Doolittle et al 1972;Eagles and Frey 1974;Campo and Rodriguez 1986) where the general finding is that response from independent culling was at least as good as that with index selection.…”

Experimental comparison between weight‐free and non‐linear indices in Tribolium

“…Experimental results comparing the best two methods of multiple trait selection have not conclusively shown the theoretical advantage of the index over the independent‐culling method. S en and R obertson (1964), D oolittle et al (1972), E agles and F rey (1974) and M c A llister et al (1990) did not obtain significant differences between the methods, while a significantly greater response to index selection was found by E lgin et al (1970) and C ampo and R odriguez (1986). The comparison between index and independent‐culling methods was contradictory in the two experiments that were carried out by R asmuson (1964).…”