More generally, the plants (and the associated microbes) are no longer seen as 'individual' but rather as a holobiont, in other words a unit of selection in evolution, a concept that holds great promise for future plant breeding programs.
Similarly, Slobodkin and Rapaport assumed that a unit of selection is something that "responds to selective forces as a unit whether or not this corresponds to a spatially localized deme, family, or population" (1974, p. 184).
Vrba, Eldredge, and Gould all defined a unit of selection as requiring an emergent, adaptive property (Vrba 1983 , 1984 Vrba and Eldredge 1984; Vrba and Gould 1986).
In sum, Dawkins has identified three criteria as necessary for something to be a unit of selection: it must be a replicator; it must be the most basic beneficiary of the selection process; and it is automatically the ultimate manifestor of adaptation through being the beneficiary.
By contrast, D.S. Wilson (1975) introduced the term "trait group" specifically to name a type of group that he thought was pervasive in nature, and that could be a unit of selection just as individual organisms were.
Darwinian natural selection identified a mechanism and – once genes had been discovered, unknown to Darwin, by a Moravian monk called Gregor Mendel – a unit of selection.
A unit of selection must replicate with high fidelity and only genes have this property.
