However, genetic engineering now enables specific alterations of single traits in already successful varieties.
Traditionally, studies of intrasexual selection have focused on single traits that are more exaggerated in males.
Very often these traits are correlated and should, therefore, be evaluated together rather than as single traits.
Since good crop varieties combine optimal values for several traits to maximize productivity and quality, multiple traits of germplasm should be evaluated during a breeding scheme rather than single traits.
The common focus on single traits rather than multiple trait combinations limits our understanding of their adaptive value, and intraspecific trait covariation has been neglected in ecology despite its importance in evolutionary theory and its likely impact on species distributions.
However, even in this work, to our knowledge no single study (i.e., one using the same species and experimental design) applied treatments that selected divergently on multiple versus single traits [50], [58].
Overall, our analyses suggest that I×E interactions may be substantial in wild populations, when measured across relevant environmental contrasts, although their detection for single traits may require very large samples, or high rates of inbreeding.
The abbreviation of single traits refers to Figure 1.
The remaining five QTL only affected single traits.
Combination of two single traits, high LDL and high TG, introduces multivariate phenotype highLDLhighTG which can amplify association strength with correlated single traits by additive effects of the single traits.
Multivariate phenotype highLDLhighTG increased the strength of phenotypic associations with the correlated single traits by additive effect of multiple single traits.
