Side effects of introducing cultivated variants of a plant into an area where the wild version grows?

Question

Plant breeders, farmers and gardening enthusiasts have for centuries been selectively breeding plants to develop plants with certain desired traits, be it larger roots or fruit, showy flowers or....

So if one chooses to plant that is the result of some breeding effort in an area where the original wild version is at home, could that have negative effects on the wildlife? Like cross-pollinating and similar? And are there methods to avoid spreading of the cultivated type?

I distinctly remember some of the wild Bellis perennis in my parents' lawn suddenly showing a double layer of ray florets and pinker tinge after pink cultivated bellis were planted in a flowerbed nearby.

Would I risk a similar effect if I planted red-leaved variant of elder (S. nigra 'Black Beauty', S. nigra 'Black Lace') in my garden, in a region where Sambucus nigra is growing wild? Short of cutting off all flowers before bloom, is there a way to avoid it? Or is the risk only theoretical?

Answer 1

If, by red leaved elder, you mean Sambucus nigra varieties such as 'Black Lace', it will have no impact on the local population of wild S. nigra. The black leaved cultivars are not self fertile, so you need two for pollination purposes, but may well produce flowers anyway if there is any other Sambucus nigra variety in the vicinity. Usually, no viable seed is produced from flowers on black leaved cultivars, and even if it is, it doesn't come true, whereas your native or endemic S. nigra will freely produce seed which will come true, so any seed which germinates won't be one of the cultivars.

Answer 2

In general the effect is minor. Natural selection already created optimum natural varieties for local environments.

Cultivated varieties are weaker, for several reasons. One is that cultivated plants have less competition (removing weeds, planting in ideal positions, watering and fertilizing). An other reasons: cultivar have less genetic variety, so easier to get diseases (it costs less to cure, than to create a new variety with all positive traits, plus resistance). But the most significant factor (according my opinion) is: cultivated plants have other strengths: big fruits, large fruits, more sugar fruits, early productions, which takes a lot more energies for less vital things, so competitors have great advantage.

Note: this is true for wild species. Bellis perennis is not so wild: grass-cutting could help them vs competitors.

Note: invasive species are different: They are not weaker version of wild plants, but probably adapted to a more competitive environment.