"Survival of the fittest" on a micro scale.
I'm not sure if this would be actually "adapting" the plants themselves or just finding occasional genetic variations that fit. I think any actual genetic changes to the plants caused by your environment would take many generations.
I save
seed from random plants/fruits/pods, I never really try that hard to select the biggest or best necessarily because this might just be an effect of the fertility of that specific spot in the garden, sunlight or water variation.
As long as the seed is mature and fully formed, I think it has as much potential as the seed from a larger plant.
One of the things I saved from last year was
tomato seed.
This Spring I split up the 30 or so plants I grew over Winter and planted them a few different areas of the
yard.
What is interesting is that one section of plants have been sickly and small and are already dying out, and one of the other tomato areas is exactly the opposite- giant, leafy, dark green and covered with tomatoes.
These plants were all from the same fruits and grew up together- but their final planting location determined how well they would do.
I guess my point was that "survival of the fittest" can depend on more factors than how healthy the ancestor plants were.
Of
course there is the possibility that out of many plants you might get some genetic "sports" or variations that just happen to fit your location better than its peers- it is just kind of hard to determine given all the other varying conditions that effect the general health of plants.