Date: Mon, 17 Jul 2000 13:05:37 +1000 From: r.jobson@botany.uq.edu.au To: cp@opus.hpl.hp.com Message-Id: <aabcdefg2132$foo@default> Subject: dispersal
Hi John and others,
I may be able to add to this discussion in about six months as I
will be doing a study of population structure (Utricularia) within a
huge river catchment in the US.
But anyway of the Utricularia, past observations (I am reading from
Taylors intro) demonstrate that birds play a huge role for dispersal
of both suspended aquatics and terrestrial species of Utricularia.
Wagner 1928 showed that turions of U. stellaris are capable of
growing after a six month period of desiccation. And there is a fair
bit of other observed evidence, I also recall reading Darwin as
saying that his buddy found U. gibba amongst feathers of ducks,
probably discussed it over a gin and tonic at the club jolly good.
The species I studied in 97 U. uliginosa have seed with intercellular
spaces that allow the to float for (my observations) many months!
This is the case for many other species also. So they float around
and get sucked up with the water tension onto the legs of wading
birds. Some rheophytes have sticky mucilage on their seed coats
and there are lots of other strange specializations about.
In regards to the re-growth after desiccation - go grab some U.
gibba and dried it out for a month or two then stick the mass back
in the water and see if it re grows - it will!!
In one experiment I had to sterilize stolons of U. uliginosa in a
dilute bleach solution. Tiny regions withstood this treatment and
became established in almost all instances. Much harsher than
drying out and remember that birds have to stop each day? for a
rest on long trips.
And finally the seed become embedded in mud (or peat) that
adheres to the feet of the birds and can be carried long distances.
If later the bird lands in a suitable habitat then the plant is away. All
this occurs over long periods as mentioned earlier. And bird routes
have changed through these long periods, as have the land masses
and habitats.
Also I remember Darwin did a small experiment with sea water and
found that for long periods? Utricularia seed survived? Can some
one add to this? Lets not forget competitive
exclusion/extinctions/habitat flux that have possible hidden forever
a once larger distribution of a specific species.
great topic
Best,
Rich.
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