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Re: Captive breeding of endangered aquatic plants.

Dear Mark Fisher,

Thank you very much for your account of the captive breeding program for
Zizania texana from the San Marcos River. I also had a look at the web
site that you referred to which was very interesting.

For those with an interest in the causes of biodiversity loss in running
waters can I recommend Allan and Flecker (1993).

Allan and Flecker (1993) stated that Zizania texana and Ptilimnium
nodosum (an annual herb in the parsley family) are the only two riverine
plants that are currently listed as endangered. They put this down to
the fact that the few species of higher plant which live in running
waters occupy a wide variety of habitats, thereby minimising their

The decline of Britain's rarest plant (Crassula aquatica) in Loch Shiel,
Scotland has been blamed on eutrophication caused by either cage fish
farms and/or rural development. It has been hypothesised that an
increase in nutrients has resulted in the selection of macrophyte
species with the largest capacity for nutrients (NCC, 1990). This
results in a decline in macrophyte species diversity and an increase in
weedy species characterised by rapid seasonal growth and large numbers
of propogules.


Allan, J.D. and Flecker, A.S., 1993., Biodiversity conservation in
running waters. BioScience, 43(1): 32-43.

NCC, 1990., Fish Farming an the Scottish Freshwater Environment. Nature
Conservancy Council, No. HF3-03-450, 12 Hope Street, Edinburgh, EH9 2AS,
285 pp.