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This chapter focuses on evolutionary implications that can be inferred from the existence of within-plant variation in organ traits and the associated ecological phenomena mediated by interactions with animals. The adaptive levels of environmental phenotypic variance in organ traits can be maintained by selection, regardless of the mechanisms producing it. Subindividual variability often accounts for nontrivial proportions of total environmental phenotypic variance of organ traits; selection by animals on variability has the potential to modify the magnitude of environmental variance and, in so doing, shift the balance between the genetic and environmental components. It is suggested that the environmental and genetic factors may be envisaged as “competing” to produce a given level of phenotypic variance. Thus, the spatial and temporal dynamics of such competition has manifold evolutionary implications, and animals can play a driving role by shifting the balance toward one side or the other.

This chapter elaborates myriad mechanisms in subindividual variability in organ traits that might in the long run have some nontrivial evolutionary consequences for the plants. It is seen that the fitness effects of within-plant variation in organ traits are not much better established to date for discrete than for continuous variation. It is shown that “division of labor” exploitation of environmental patchiness or partitioning of environmental gradients need not be restricted either to discontinuous variation or to the partitioning of the physical, abiotic environment. The biotic environment represented by pollinators or seed dispersers is also susceptible to partitioning, or “division of labor,” by structures borne on the same plant performing the same function but differing slightly in their phenotypic characteristics.

This chapter articulates subindividual variability as an individual property in the format of the Haldane-Roy conjecture that describes within-plant variability in organ characteristics denoting a significant shift of opinion about the importance of a phenomenon. The verification of the Haldane-Roy conjecture, and its reinforcement by indications of a genetic basis of within-plant variation, should impel us to change the ways in which the individual plant phenotypes are characterized. Within-plant variance should be granted a descriptive value of the phenotype similar to the value traditionally conferred on the within-plant mean of organ trait values. Hence, acceptance of the Haldane-Roy conjecture opens the way to examining variation among characters, among species, and among populations of the same species, also from the perspective of their levels of within-individual variability.