Thanks David
Yes - I'd seen the "interstate corridor" paper, but I don't fully buy
the idea that it is D. fullonum's primary natural dispersal method.
Perhaps I have to accept that there isn't a "primary" method but are a
number of lesser methods. I'll keep looking and I'll be checking out
the finch crap come the autumn!
Cutting a couple of heads in half to check on seed development
yesterday I found 2 out of 3 with larvae hollowing out the pith in the
centre. A quick search suggests 1 of 2 or 3 species of moth larvae.
I can't imagine a more protected place for a little grub to live (until
I come along that is!).
Next I have to work out the best way to quantify reproductive fitness.
Ideally I would count every seed on each experimental teasel and then
plant a random sample to find a germination rate. Unfortunately I have
just the one life so I may need to find a way of cutting the work down
to manageable levels.
Alarm bells go off in my head when I read . "A single teasel plant can
produce over 2,000 seeds; up to 30-80% of the seeds may germinate.
Seeds may remain viable for at least 2 years." and then find the same
wording repeated over & over. It just sounds too much as if one
unrefferenced source is being quoted as gospel over and over. Nothing
for it but to get a huge sheet, a teasle plant and some seed trays I
suppose! I just hope the moth larvae aren't having too much effect on
seed production. If they do they will really mess up my plans!!
Thanks for the help - I'll try & remember to post a link to my
dissertation when it's done in 18 months!
Cheers
Ian
In article . com,
wrote:
A google.com search on Dipsacus dispersal produces a lot of hits. It is
an invasive species in the U.S. and Canada so has been studied a lot.
The study "Dispersal of Dipsacus laciniatus seed along an interstate
corridor and a natural area" by R. N. Wiedenmann ) and
A. Musser, Illinois Natural History Survey and J. D. Parrish, Millikin
University concluded it was wind dispersed and traveled a maximum of 15
meters along a highway.
http://66.102.7.104/search?q=cache:V.../ncr125/StateR
pts2002IL.htm+Dipsacus+dispersal&hl=en
The following webpages indicates other important modes of dispersal as
water, highway mowing equipment, highway construction, cultivation and
humans disposing of flower arrangements containing teasel. It has
spread particularly along the interstate highway system. Its use in
flower arrangements is blamed for its spreading to cemetaries.
http://dnr.wi.gov/invasives/fact/teasel_com.htm
http://www.inhs.uiuc.edu/chf/outreach/VMG/teasel.html
http://www.mdc.mo.gov/nathis/exotic/vegman/ten.htm
Dipsacus fullonum L. was named by Linneaus (1707-1778). William Hudson
(1730-1793) seemingly believed D. sylvestris Huds. represented a
separate species because the bracts on the receptacle have a straight
barbed awn according to Bailey's Manual of Cultivated Plants. D.
fullonum seems to have a recurved awn. Such a minor difference is
apparently not considered enough to represent a separate species by
most taxonomists today so D. sylvestris is either a subspecies,
Dipsacus fullonum subsp. sylvestris, or merely a synonym for D.
fullonum. The references that are listing D. sylvestris seem out of
date. Britton and Brown's influential 1913 flora listed D. sylvestris
as did Asa Gray's 1908 Manual of Botany so that may have given the name
staying power. You might try to look up Hudson's original description
for D. sylvestris and see why he thought it was a separate species from
D. fullonum or if it was merely a case of his independently describing
the same species as Linnaeus given that were contemporaries.
The following reference says in the U.S., D. sylvestris is used for the
cultivated teasel and D. fullonum for the wild teasel. The opposite is
done in Europe.
http://ucce.ucdavis.edu/files/fileli...5319/17400.pdf
Dipsacus is not usually considered carnivorous because it has no
enzymes to digest trapped animals. I'm not sure if there have been
research studies that examined if the trapped animals provide a benefit
to the plant. I'm sure it's possible that they could provide a small
benefit because foliar fertilization of plants can be beneficial. Tank
bromeliads can drown animals too but they are not usually considered
carnivorous. The phenomenon of plants retaining small, open pools of
water is termed phytotelmata.
http://www.canopyants.com/treehole.html
http://bromeliadbiota.ifas.ufl.edu/bromfit.htm
You might wish to check the following databases for Dipsacus:
http://www.ingentaconnect.com/
http://www.pubmedcentral.nih.gov/
http://agricola.nal.usda.gov/
David R. Hershey