The variational properties of an organism, as distinct from its functional properties, are those properties relating principally to the production of variation among its offspring, but in a broader sense can include phenotypic plasticity. It is an umbrella concept introduced in [1] [2] [3] so that the classical concepts of pleiotropy, canalization, developmental constraints, morphological integration, developmental homeostasis, etc., and later concepts such as robustness, neutral networks, modularity, the G-matrix, distribution of mutation effects, etc., could be thought of as different aspects of a single phenomenology. While the functional properties of an organism determine is level of adaptedness to its environment, it is the variational properties of a species that chiefly determine its evolvability.
Variational properties include the production of DNA sequence variation, epigenetic variation, and phenotypic variation. While the genome is typically thought of as the storehouse of information that generates the organism, it can also be seen as the set of heritable degrees of freedom for varying the organism. DNA thus has both a generative role in the organism, and variational role in the lineage.
Prior to its introduction into evolutionary biology, the phrase "variational properties" already had usage in various areas of mathematics[4] and physical sciences [5] [6]