Favorite Plant Sources
Paul Licht (Thu, 29 Jul 2010 18:58:29 PDT)

Tim
You raise a number of issues. First, I don't know of any strict
definition of biodiversity that would fit a survey; it depends partly on
the question being addressed. My initial attempt was to assess
phylogenetic diversity at a 'high' level. It's amazing how little we
know even at this crude level.

Botanical gardens/arboreta generally focus on vascular
plants--primarily ferns and seed plants. One can speak of biodiversity
at all levels. Families are actually tricky to evaluate since the
taxonomy is very much in flux (e.g, a lot of families may be folded
into* *or removed from *Liliaceae*) and not all gardens are using the
same system; we could increase or decrease our number by adopting
different systems but overall, we are on the conservative side. Generic
designations are more consistent and most gardens use a similar species
designation (however, in our University herbarium the species concept
for plants has been challenged). Much more complex is the use of
'taxa'. I included this designation in my survey but the interpretation
is too difficult. In our collection, taxa refer primarily to recognized
naturally occurring subspecies and varieties, but in many, they include
an undetermined number of horticultural cultivars (many gardens count
each cultivar of daylily, rose or Nerine, etc. which we do not).
Consequently, I tend not to use this category; several gardens list
20-30,000 taxa even though they have a relatively few actually species .

Many other issues have to be considered. We think that having provenance
and direct wild-collected origin is important for research and
conservation but not many gardens focus on this issue.

Studies have shown that to have a meaningful representation of a
population gene pool, you may need 50+ individuals which few gardens can
afford. Alternatively, could we argue that we have accomplished the same
thing by having 50 individuals of a species distributed over many
gardens--only if we actually knew what each garden had. Unfortunately,
it is highly likely that many gardens have many of the same species.
Thus, out of the total 250,000-320,000 recognized species, garden
collections barely touch the surface: we're all long way from filling
"Noah's plant ark".

Given the threat to flora worldwide, it is imperative that we share and
distribute good material (for us this means wild collected with
provenance) among bonafide collections with some degree of assurance
that they will be supported in the future. Regrettably, private
collections don't easily lend themselves to being part of such a
biodiversity genebank.

Paul Licht, Director
Univ. California Botanical Garden
200 Centennial Drive
Berkeley, CA 94720
(510)-643-8999
http://botanicalgarden.berkeley.edu/

On 7/29/2010 9:59 AM, Tim Harvey wrote: