Should I plant plants from a cultivated source if I am trying to preserve wild populations of the same plant? Next to where I want to plant Baccharis pilularis, there is a wild, native stand of Baccharis pilularis. Say that I import genetic material of a plant like Baccharis pilularis from a nursery or from a wild population hours away. If the imported plants achieve reproductive maturity and cross with the wild Baccharis pilularis, will the wild plants have reduced fitness?
How is local adaptation measured?
Could hybrids have reduced fertility? Will pollen of the original plants and offspring be of inferior quality? Is that a concern if pollen of reduced quality? Since dryer conditions favor fast-emerging seeds, it seems that imported propagules bred over the course of years in wetter conditions will produce offspring that are less likely to succeed in the wild due to the slower emergence of seeds (Arakelian, UC Merced).
Do cultivated “native” plants have reduced genetic variation?
I think the answer is fairly complicated–as it can only be addressed by evolutionary theory, and there are several evolutionary mechanisms involved. Plants with traits that allow them to produce more offspring will logically pass more of their genes to the next generation, therefore the trait that conferred the reproductive advantage will be more common in the next generation (= natural selection). The opposite is true as well. Plants with traits causing them to produce fewer offspring will pass fewer of their genes to the next generation, therefore that trait will be less common in the next generation. This process is what leads to adaptation. Local adaptation is measured by how many offspring are produced, because adaptation is defined as traits that improve reproductive success in the local environment.
You don’t have to worry that a poorly adapted trait will become more common unless the wild population is small. Then, by chance, the poorly adapted trait can become more common (that’s called genetic drift). Genetic drift, like natural selection can cause traits to increase or decrease in frequency, but it has nothing to do with benefit or harm, rather, it’s drive by chance alone. Some plants will produce more offspring than others just by chance. Chance effects are more profound in very small populations, but hardly noticeable in large populations.
Perhaps of greater concern is if the cultivated plants might be hybrids with an exotic species. Unfortunately, horticulturists are hybridizing native species with closely related exotic species to create new varieties. Those hybrids are often not good at reproducing, but sometimes they are. Exotic genes could then escape into the wild population–but only if the exotic genes allow the plants to produce more offspring (meaning, if they are more well adapted–again, detrimental traits will not increase in frequency, they will decrease in frequency by natural selection. Detrimental traits will only increase in frequency if the population is small, by genetic drift).
Cultivated plants do have reduced variation, but you cannot “introduce” reduced variation into a wild population. It’s only the exotic genes that you have to worry about introducing.
an Asteraceae … these typically produce many many seeds
Well, I think in this case the answer might be simple: Why not use seed from the nearby population instead of planting horticultural varieties? Using locally collected seeds, you will certainly not introduce unwanted or untypical traits. And your planting will attract birds and insects that feed on seeds … as opposed to a pure “male” stand of cultivars, that will neither attract seed eating birds, nor recruit more plants (just spreading its genes into the wild population).
It much depends on the scope of the plantation.
In the case of reinforcement, ideally, plants should be genetically as much as possible similar to those already present in the site. In this light, plants should be raised from seeds collected in the population to be reinforced.
In the case of reintroduction, plants should be genetically as much as possible similar to those growing in the proximity of the site.
In the case of ornamental planting, plants are often of unknown origin and it would be great to make them not get in contact with the local strains.
Yes absolutely. I raise CA native plants for sale. For many of them, all the individuals are genetially identical, having been rooted from cuttings, not grown from seeds. This is especially true if the plant is a named cultivar; new indivduals must be identical in order for the cultivar name to go on them.
Some species are more likely to be grown from seed than others, but at least in my case, the seed source could be just one or two parent plants.