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BEN # 215

Adolf Ceska aceska at VICTORIA.TC.CA
Sun Feb 21 22:10:04 EST 1999

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No. 215                              February 21, 1999

aceska at freenet.victoria.bc.ca        Victoria, B.C.
 Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2


This  Symposium  is  organized  by  the  School of Environmental
Studies and Restoration of Natural Systems  Program,  University
of  Victoria,  in Partnership with The Pacific Wildlife Research
Centre of The Canadian Wildlife Service and The Garry Oak Meadow
Preservation Society.

The Garry Oak Meadow constitutes a major  distinctive  ecosystem
complex  in  North  America.  Today  these  ecosystems are under
serious threat from urban growth, land management practices  and
invasion  by  exotic  species. The threats to these biologically
diverse ecosystems are particularly acute in the  only  area  of
Garry Oak Meadow in Canada, on southern Vancouver Island and the
Gulf  Islands. Interest and concern about this special ecosystem
complex in Canada and adjacent United States has grown  dramati-
cally.  We  invite  you  to join us in a Symposium and Community
event to learn about and celebrate our Garry Oak Meadow  ecosys-

We  will  be addressing issues concerning biology, ecology, eth-
nobotany, management, restoration, conservation, protection  and
education  of Garry Oak Meadow ecosystems. In celebration, there
will be art exhibits, music, festivals, story  telling,  dancing
and  children's activities and much, much more focusing on Garry
Oak ecosystems.

We will have special speakers  representing  of  the  Garry  Oak
ecosystems  from  California  to British Columbia and from other
Oak ecosystems too. If you are interested in  participating,  or
for  further information, please contact UVic Conference Manage-
ment or consult our WEB page:


You are welcome to present a Poster (to be mounted on a 4' x  4'
board)  on any topic related to Garry Oak ecosystems, please see
the following WEB site for details:

For more information contact:

Pat  McGuire,  Conference  Management,  Division  of  Continuing
Studies, University of Victoria, P.O. Box 3030. STN CSC,
Victoria, BC, Canada V8W 3N6
Phone: 250-721-8746; FAX: 250-721-8774, E-mail: pmcguire at uvic.ca

From: Melanie Marshall <melaniem at io.com> &
      Fred Ganders <ganders at unixg.ubc.ca>

Henderson's  checker-mallow,  Sidalcea  hendersonii  Wats. (Mal-
vaceae) is a perennial herb inhabiting low elevation wet meadows
and tidal marshes from southwestern British Columbia to  Oregon.
In  British Columbia, Sidalcea hendersonii is listed as "blue" -
vulnerable (Douglas et al. 1998). This designation is  used  for
indigenous species of special concern because of characteristics
that make the species particularly sensitive to human activities
and  natural  events.  Several factors contribute to the plant's
rarity including human encroachment into wetland habitats,  dis-
placement by aggressive invasive species such as Lythrum salica-
ria, and insect seed predation.

Sidalcea  hendersonii  is gynodioecious. This is a mating system
whereby  populations consist of separate  coexisting  hermaphro-
ditic individuals and female individuals.  Hermaphroditic Sidal-
cea hendersonii flowers  contain  both  functional  anthers  and
ovaries,  are  self-compatible  but  protandrous. Female flowers
have functional ovaries but nonfunctional stamens. In  gynodioe-
cious  species,  female plants would seem to have a reproductive
disadvantage relative to hermaphrodites since they do  not  con-
tribute genes through pollen (Lewis, 1941). Females must produce
significantly  more seeds than hermaphrodites for male sterility
mutations to be maintained in gynodioecious  populations  (Char-
lesworth and Ganders, 1979).

We  investigated the genetic and ecological factors contributing
to the maintenance of females in British  Columbian  populations
of  Sidalcea  hendersonii  - see Marshall 1998. Crossing experi-
ments indicated that male sterility is controlled by a  dominant
nuclear  allele.  High  frequencies  of  female  plants  in  the
majority  of  populations  surveyed,  in  combination  with  the
nuclear  determination of sex, elevates the theoretical require-
ments for female fitness  in  this  species.  Females  did  have
higher  fitness,  producing  more  surviving offspring than her-
maphrodite plants in an  experimental  population.  However,  no
inherent  fitness advantages were evident in natural populations
where females and hermaphrodites did not differ in  viable  seed

Two  species  of  Curculionid  beetles  (weevils),  Macrorhoptus
sidalcea Sleeper and Anthonomus melancholicus Dietz,  parasitize
the  flowers  of  Sidalcea  hendersonii in British Columbia. An-
thonomus melancholicus is restricted to populations of  Sidalcea
hendersonii  located on Vancouver Island, where the frequency of
females was unusually high. In populations where  female  plants
were  abundant, weevil larvae destroyed significantly more seeds
from hermaphrodite plants, substantially reducing  hermaphrodite
seed  production  overall. The extent and mode of seed predation
was dependent upon which  weevil  species  was  present  in  the
population.  In  populations  where  Macrorhoptus  sidalcea  was
present, the seed was only partially consumed. While M. sidalcea
larvae feed on the interior of the seed, creating small  tunnels
in  the  seed  coat,  Anthonomus  melancholicus larvae appear to
consume the entire fruit. Sex-related predation was evident only
in  populations  where  Anthonomus  melancholicus  occurred  (on
Vancouver  Island)  and was correlated with the more destructive
feeding pattern of this weevil.

The basis for discrimination between flower types was not inves-
tigated, but adult A. melancholicus weevils are likely attracted
to hermaphrodite  flowers  because  hermaphrodite  flowers  also
contain  pollen,  a  known  food  source. Extensive predation of
hermaphrodite seed could  provide  the  necessary  advantage  to
females  of  Sidalcea  hendersonii. To our knowledge, this study
provides the first evidence that sex-related  predation  may  be
responsible  for  high female frequencies in natural populations
of a gynodioecious species.


Charlesworth,  D.  and  F.  R.  Ganders.  1979.  The  population
   genetics of gynodioecy with cytoplasmic-genic male-sterility.
   Heredity 43(2): 213-218.
Douglas,  G.W.,  G.B  Straley, & D. Meidinger. 1998. Rare native
   vascular plants of British Columbia.  B.C.  Ministry  of  En-
   vironment, Lands & Parks, Victoria, B.C. 423 p.
Lewis,  D.  1941.  Male sterility in natural populations of her-
   maphrodite plants. New Phytol. 40: 56-63.
Marshall, M. 1998. The maintenance  of  gynodioecy  in  Sidalcea
   hendersonii.  M.Sc.  Thesis, Department of Botany, University
   of British Columbia, Vancouver, B.C. ix+100 p.

Authors: Melanie Marshall (1) and Fred R. Ganders,
   Botany Department, University of British Columbia, Vancouver,
   B.C. Canada V6T 1Z4
   (1)Current address:  Zilker  Botanical  Garden,  2220  Barton
   Springs Rd., Austin, TX 78746 USA

From: Adolf Ceska <aceska at victoria.tc.ca>

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