Favorite Plant Sources

Paul Licht plicht@berkeley.edu
Thu, 29 Jul 2010 18:58:29 PDT
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

On 7/29/2010 9:59 AM, Tim Harvey wrote:
> I am quite interested in methods to measure plant collection diversity. Is your score a simple sum? Are all genera considered equally diverse?
> How do you know what everyone else has?
>   Tim
>> Diversity was measured by the #families, #genera, #species in the
>> collection. The UC Garden tops all other N. American gardens in the
>> families and genera and has the 3rd largest number of species. However,
>> it appears our collection is unequaled based on the number of
>> acquisitions with provenance (of wild origin)k. In fact, we would easily
>> have greater diversity if we didn't adhere to our policy of wild
>> collected material with provenance. In thinking of this, it is a way
>> that PBS may help us build the collection. We could discuss this issue.
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