If an adaptive trait is controlled by several gene loci, what can be inferred about its variability?

The assertion that an adaptive trait controlled by several gene loci is more likely to be quantitatively variable is grounded in the understanding of polygenic inheritance. When a trait is influenced by multiple genes, each contributing a small effect, this often results in a continuous range of phenotypic expression, rather than discrete categories.

Quantitative traits can exhibit a wide range of variations among individuals, such as height or weight, because the cumulative effect of many genes can result in slight differences that manifest as a spectrum of outcomes. Therefore, multiple loci leading to an adaptive trait suggest that there is substantial genetic variability present, facilitating the possibility for natural selection to act upon this variability and promote adaptability in changing environments.

This characteristic differentiates such traits from qualitative traits, which tend to fall into distinct categories and are typically controlled by a single gene. Furthermore, the assertion that the trait would show no variability or is influenced solely by environmental factors does not align with the genetic basis of adaptability, as variability comes from genetic influences. Thus, the presence of multiple loci controlling an adaptive trait indeed indicates a greater likelihood of quantitative variability.