Yes, the visible characters of the plant constitute the phenotype. The
geneotype is always hidden from view and can only be determined indirectly
(such as through a controlled crossing experiment). Even allozyme analysis
gives you a "gel migration phenotype".
> Hybrids, whether or not they are naturally occuring, do not
> contribute to conserving a species. Sure, they preserve part of the
> genetic makeup of that species, but the species is lost if its DNA is
> only represented in hybrids.
And there is no easy way (no way at all?) to recreate the parental
species from a hybrid population. We might artificially select for
phenotypes which resemble the parentals, but the effort would be
problematic. Better to spend the time protecting existing species.
> Finally, how many species in culture now are derived from only a
> few or a single wild collected parent? How many of us grow large numbers
> of representatives of any single species? My feeling is that the number
> of people growing more than a few, or in many cases more than a single
> plant, of a particular species is probably very small. And many of those
> with multiple representatives of a particular species generated all those
> plants from a single, or at most a few parents. This just does not
> represent much diversity.
These are very important considerations. I wonder if anyone here has
worked with the Atlanta Botanical Garden's CPC (Center for Plant
Conservation) program? The CPC attempts ex-situ conservation, and
it would be useful to consider how they are attempting to preserve
genetic diversity. I have a hunch they put a large emphasis on
seed banking. The CPC has a web page, which should have some
useful background, but I'm not sure if they go into procedural
details there.
>From my experience with the Desert Botanical Garden's CPC collection, I
know the program places a strong emphasis on growing many genetically
different representitives of the same species (even populations
in the species). The living plants are randomly crossed between all
members of the population to produce seeds which preserve this genetic
diversity, while still attempting to maintain the genetic integrity of
the different populations. The seed bank is better for preserving
a lot of genetic diversity than living plants, because seeds take up
so much less space, and more can be maintainted. But seed viability is
a concern, and plants must be grown up from the seed bank periodically.
To avoid selection for adaption to cultivation, the plants are grown
under conditions which approximate the habitat (especially by growing
the plants outdoors when possible). The CPC is set up with the member
botanical gardens working with rare plants from their local geographic
area.
Michael Chamberland