If you propagate your plants asexually, you will not have to worry about this at all. You could create a nursery with one mother plant!!

As far as the pollinating question, you are asking something a little bit to broad to be answered in a simple forum. I'll address one issue: many of the flowering plants that we purchase today are hybrid crosses. They will not reproduce true from seed. Others are grafts or otherwise cloned and will not reproduce true from seed.

You might want to make a list of the specific plants you are interested in and do an individual search on reproduction of each.

1. Would the plants own flowers have a good chance of polinating themselves with eachother?

Since pollination is only the physical act of a pollen being placed on the stigma. The possibility is high. Whther or not fertilization occurs would depend on the plant some plants have chemical mechanisms that prevent self fertilization. Or if you planted one of the few plants that only produce only flower of one sex on the same plant self fertilization would be impossible.

2. More importantly, would i be able to form a healthy population, several generations, from a single flowering plants - or is the fact that all of the resulting generations comming from a single plant would be weaker in some ways then if i were to have a group of plants fertilizing eachother and introducing diversity to the gene pool?

The health of the the resulting population would depend on the heterozygosity of the original plant. If the original plant was severly inbred you may see some weakening of the plant population. Since the offspring from the first plant would have some genetic diversity there would always be some variation in the plants. A group of plants may not be gentically diverse to begin with. If you started with a group of plant that were asexually propagated or a group of F1 hybrids created from inbred lines you would have the same results as if you started from a single plant.

Other things that would effect the results would be if you were using an annual or a perennial. If using perennials you would have the possibilty of offspring breedins with the parent. Also generation time would effect the results.

Would the plants own flowers have a good chance of polinating themselves with each other?

That depends on the particular species because some species are primarily self-pollinators and others are primarily cross-pollinators. There are some species that must be cross-pollinated. And then there are other species that may self-pollinate or cross-pollinate.

The species that must be cross-pollinated have what are called self-incompatibility genes that cause self-pollinations to fail.

More importantly, would i be able to form a healthy population, several generations, from a single flowering plants

For self-pollinating plant species the answer is yes - that is their normal method of producing seed and the offspring will be perfectly normal.

For plant species that must cross pollinate no offspring will be produced.

For plant species that permit both types of pollination the offspring will be inbred and that produces some individuals with problems. As long as the individuals that are unhealthy/abnormal/poor are removed from the group before they flower you will be selecting for vigour and that will help balance the original inbreeding and help produce a healthy population. There would need to be a balance between the number of plants left to grow and the number you remove. If you remove too many you increase the potential inbreeding level; if you remove too few you increase the loss of vigour in the population.

Taking cuttings of the original individual plant and growing a large number of identical (clones) plants will leave the possibility that all of them might die if the environment changes and they are not adapted to the change. A mixed (genetically) group of offspring (even from a self-pollinated plant) will have genetic variability and some chance of surviving such changes.

Hi,
Would you say it would be better for me to populate my yard with seedlings that came from a single mother plant (i.e. Phlox divaricata, Spigelia marilandica, Iris cristata), or to get plants of these species from two distinct regions (ecotypes - TN and WI, for instance). The first solution may cause inbreeding depression, whereas the later may cause outbreeding depression and ecotype hybrid vigor, followed by decline (F2, etc.)

Thank you.

I can't really understand what you are asking. Some phrases even seem not to have valid meaning to me.

Having multiple plants vegetatively produced from a single plant is the same as having one single, really large plant. Having a monoculture of sexually produced offspring from a single cross may increase the possibility of disease and pest susceptibility, but is not an unusual or unnatural thing. In nature, we often find local populations with limited genetic diversity. Hybrid vigor is a relative phenomenon and usually more pronounced in cases where very different genotypes (eg two different but sexually compatible species) are bred together.

njbiology, I find it understandable when I think of:
Seedling: a young plant, growing from a seed.
Seed: an embryo whose genotype has contributions from two 'parents'. Each seedling in the same generation is genetically different from the others.
Clone: a plant that is obtained from its 'mother' - vegetatively. Examples are rooted cuttings, layering, marcottage and some others that I cannot remember. In this type of propagation the genotype is exactly the same as the mother plant.
Progeny from seed produce variation and vigor which aid in the survival of the species. Horticulture.
Vegetative reproduction results in uniformity, monoculture and species decline. These can be important in Agriculture.

Hmmm, none of that helps me understand the parts of NJ's post that I didn't understand. To start with, what is the point of the inquiry? Multiple plants, with common parents, in one yard is not going to cause species decline. Monoculture is not about the parents of a few plants, but is about a large area covered with a single type of plant. Unless there's going to be some kind of multi-generation study or breeding program, what is the significance of provenance diversity in regards to offspring and genetic depression. I was just trying to figure out where NJ was coming from.

Hi,

My situation is this:

I have a few instances where I only have a small handfull of specimens representing a given species. In EACH of these cases, the species is capable of self-pollination , a perennial, and was a seedling from a population where there were many of its type... maybe a genetically diverse population, or one that is not; but one where there were at least 50 plants of its kind at the site when seed was gathered.

For instance, a few pickerel rush (pickerelweed -- Pontederia cordata), Turk's cap lilly (Lilium superbum) and broad-leaf arrowhead (Saggitaria latifolia), etc. plants. They are genetically distinct, as they are seedlings that came from several different mother plants of the same population; not vegetatively propagated clones. I am not interested in vegetatively propagating these plants; I'd like to form healthy, self-sustaining populations in my garden/garden pond from these plants -- one which will last a life-time and not result in inbreeding depression in decades to come. As long as I remove plants which are obviously un-healthy (hard to determine, of course), can I form a population (maybe 20 plants representing each of the 3 mentioned species) that will live to continue to produce future progeny to replace them as they sometimes die out.

Even though its a managed garden, I feel that a perennial plant will not last decades, so the seedlings should be heathy enough to replace the parents and themselves produce likewise healthy offspring. I like the concept, even if not practically necessary, that the plants I have in the project are genetically diverse and healthy - all derived from plants found on a single site, so all related. These are not very rare plants, so I doubt inbreeding depression is a serious risk.

On the other hand, there is a site that has a 100+ wild columbine, but the site is a bit of a natural impoundment, so the many parents from which the seeds were taken could be low in diversity, I suppose.

What do you think? Is this scenario: 5 parent plants (or even 1 in some cases.. say if I have seed given to me of a rare plant from a less genetically diverse population) ok?

Especially on a small scale (in a single garden), other factors (disease, pests, weather, etc) would vastly outweigh any concerns regarding genetic depression brought on by a lack of genetic diversity (at least for most plants). Although, the lack of genetic diversity could add to the other problems. For instance, if a parent plant was more attractive to a predator or susceptible to a pathogen, that could increase the likelihood of the entire population suffering from the problem. Genetic depression is probably the least of your problems if the plants are self-pollenizing.

Whenever a population is closed inbreeding increases with each passing generation. The rate at which it does depends on the number of effective parents in the population. Whether inbreeding produces inbreeding depression and the size of its effect depends on the natural reproductive system of each species. Even though a species may be able to be self-pollinated the important factor is whether it preferentially self-pollinates in natural populations.

Lilium superbum is noted by Fryxell as being self-incompatible (FRYXELL, P., A. 1957. Mode of reproduction of higher plants. Bot. Rev. 23: 135-233.)

Pontederia cordata has a tristylous system. These are specifically designed to prevent self-pollination and foster cross-pollinations (ANDERSON, J. M., and S. C. H. BARRETT. 1986. Pollen tube growth in tristylous Pontederia cordata (Pontederiaceae). Can. J. Bot. 64: 2602- 2607.)

Sagittaria latifolia has monoecious and dioecious populations. Dioecious plants have separate sexes and thus require cross-pollinating. Monoecious plants have both sexes on the same plant (often in the same flower). There is strong inbreeding depression and strong selection against inbred individuals even in monoecious populations (The evolution and maintenance of monoecy and dioecy in Sagittaria latifolia (Alismataceae), Evolution, 56(1), 2002, pp. 31-41).

These are not species that have evolved to be healthy/fit when inbreeding. Having said that neither mice nor corn are inbreeders yet there are relatively healthy inbred lines of mice and corn. The catch is that there has been very strong selection to get those inbred lines. The danger when inbreeding occurs is that the inbred population dies out. Strong selection has to be applied by the breeder or the person managing the population to maintain the fittest individuals. When producing inbred lines that means starting out many different lines knowing that many will die out but a few will remain. In a managed population that may mean hand-pollinations to produce replacement seed from parents of known and lowest inbreeding values. Or introducing new unrelated individuals from other compatible sources as in species survival plans.

I had to stop reading and wait for the pop up add to get out of the way. Very difficult to build a train of thought with such constant interuption. Who decided that was a good business strategy?