Cultigen - Critique of Definition

Critique of Definition

Potential misunderstandings and questions arising from the definition of cultigen given here have been discussed in the literature and are summarised below.

• Natural and artificial selection

The selection process is termed "artificial" when human preferences or influences have a significant effect on the evolution of a particular population or species (see artificial selection). Note: artificial selection is a part of the overall selection process - it does not imply that humans are not part of nature, it is simply useful sometimes to distinguish when there has been human influence on selection (as with cultigens).

• What exactly does altered mean?

There are cases that do not seem to comply with the definition. For example, we can presume that the entire global flora is changing as a result of human-induced climate change. Does this mean that all plants are cultigens?

In cases like this the definition refers to "deliberate" selection and this would be of particular plant characteristics that are not exhibited by a plant's wild counterparts (but see Selections from the wild).

• What exactly does deliberately selected mean?

From the moment a plant is taken from the wild it is subject to human selection pressure - from the selection of the original propagation material to the purchase of the plant in a nursery. Surely this form of selection is not deliberate? Again, the early human selection of crops 7,000-10,000 years ago is thought to have occurred quite unintentionally. Variants useful to horticulture often arise spontaneously, they are not deliberate products. Are these cases of unintentional, accidental, or unconscious selection?

There certainly appear to be cases where origin or selection of a plant is not "deliberate". However, the long term propagation of plants that have some utility, usually economic or ornamental, can hardly be regarded as unintentional and these plants will, almost without exception, have characteristic(s) that distinguish them from their wild counterparts.

• What about plants selected from the wild?

Plants like Quercus robur, Pedunculate or English Oak, Liquidambar styraciflua, Sweetgum and Eucalyptus globulus, Blue Gum grown in parks and gardens are essentially the same as their wild counterparts and are therefore not cultigens. However, occasionally within natural plant variation there occur characters that are of value to horticulture but of little interest to botany. For example a plant might have flowers of several different colours but these may not have been given formal botanical names. It is customary in horticulture to introduce such variants to commerce and to give them cultivar names. Technically these plants have not been deliberately altered in any way from plants growing (or once growing) in the wild but as they are deliberately selected and named it seems permissible to refer to them as cultigens. These occurrences are very few. The definition could be (clumsily) extended by mentioning that selection can be for "desirable variation that is not recognised in botanical nomenclature" (which excludes those plants simply transferred from the wild into cultivation).

• What about gene flow between populations?

Occasionally cultigens escape from cultivation into the wild where they breed with indigenous plants. Selections may be made from the progeny in the wild and brought back into cultivation where they are used for breeding and the results of the breeding again escape into the wild to breed with indigenous plants. Lantana has behaved much like this. The genetic material of a cultigen may become part of the gene pool of a population where, over time, it may be largely or completely swamped. In cases like this what plants are to be called cultigens?

Whether a plant is a cultigen or not does not depend on where it is growing. If it complies with the definition then it is a cultigen. Cases like this have always been difficult for botanical nomenclature. Unnamed progeny in the wild might be given a name like Lantana aff. camara (aff. = having affinities with) or may remain unnamed. Its cultigenic origin may or may not be recognised by the allocation of a cultivar name.

• Plants of unknown origin

Occasionally plants will occur whose origin is unknown. Plants growing in cultivation that are unknown in the wild may be determined as cultigenic as a result of scientific investigation, but may remain a mystery.

• Difficult cases

It may happen that a hybrid cross that has occurred in nature is also performed deliberately in cultivation and that the progeny appear identical. How do we know which plants are cultigens?

If the cross in cultivation is followed by deliberate selection and naming then this will indicate a cultigen. However in a case like this it may not be possible to tell.