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Re: [beemonitoring] Redbud seed set

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  • Sam Droege
    Peter: Another interesting facet to the Redbud. It strikes me that slow-motion videography would be very revealing here. It looks like there are a number of
    Message 1 of 4 , Aug 26, 2010
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      Another interesting facet to the Redbud.   It strikes me that slow-motion videography would be very revealing here.  

      It looks like there are a number of issues surrounding the use of Cercis as a pollination set indicator that needs resolving, but they are seem tractable, and, in the scheme of things may be a more reliable easy to use measure for at least one group of the bee fauna (e.g., bees that pollinate Cercis) than actually trying to track bees directly.  So, perhaps, if there is interest out there, we can form a little redbud group that tackles the question of Cercis uses in indicating pollinator health.  I am sure there are more questions, but since the tree is so readily available to many of us, blooms at the peak of bee populations, has what appear to be nice sampling characteristics, is attractive to look at, is recognizable by almost everyone, and the blooms are edible (a side treat) it may be worth pursuing at least the question of its qualities.  It also would be a nice little intersection between bee and plant people.  


      Sam Droege  sdroege@...                      
      w 301-497-5840 h 301-390-7759 fax 301-497-5624
      USGS Patuxent Wildlife Research Center
      BARC-EAST, BLDG 308, RM 124 10300 Balt. Ave., Beltsville, MD  20705

      Hui Tzu said to Chuang Tzu:  "I have a big stinktree in my garden.   The trunk is so bent and knotty that nobody can get a good straight plank out of it.
      The branches are so crooked you can't cut them up in any way that makes sense.  There it stands beside the road and no carpenter will even look at it.  
      Such is your teaching, Chuang - big and useless."
      Chuang Tzu replied: "Have you ever watched the wildcat crouching, watching its prey?   This way it leaps, and that way,
      high and low, and at last - it lands in the trap.  Have you ever seen the yak?   It is great as a thundercloud, standing in his might.
      Big?  Sure.  But, he can't catch mice!  So for your big tree.  No use?   Then plant it in the wasteland - in emptiness.  Walk idly around it and rest under
      it's shadow.  No axe or saw prepares its end.  No one will ever cut it down.   Useless?  You should worry!.
      -  Chuang Tzu, The Useless Tree, circa 200 B.C..  
      P Bees are not optional.

      From:Peter Bernhardt <bernhap2@...>
      To:Sam Droege <sdroege@...>, tucker@...
      Date:08/26/2010 09:55 AM
      Subject:Re: [beemonitoring] Redbud seed set
      Sent by:beemonitoring@yahoogroups.com


      Dear Sam:

      Within the study of floral evolution the big question isn't whether Cercis is bee-pollinated.  The big question is whether Cercis is pollinated by bees "tripping" the flowers when they land on them and forage.  

      Let me explain.  The floral morphology of the Cercis flower is intermediate between a true papilionoid tripped flower (like a clover or pea) and a caesalpinoid flower that requires no tripping because the anthers dehisce before the bee arrives or are vibrated (as in partridge peas-cassias).  My colleague, Shirley Tucker, an authority on floral development in the legumes asked me to look at the process years ago but I never had the time although the trees are very common at the Missouri Botanical Garden.  We could answer this question this Spring if enough people watched the process and took the same series of observations.  Tripping does two things.  First, the bee's pressure on floral keel (where stamens and anthers are wrapped up) forces the dehiscent stamens to move upwards and strike the bee on its vent.  Second, the pressure causes the membrane on the pistil tip to rupture exposing it to pollen.  Does Cercis need tripping?  If so, do all bees visiting the flowers cause tripping or does it only work with bees that are a specific size and weight?


      On Thu, Aug 26, 2010 at 6:48 AM, Sam Droege <sdroege@...> wrote:


      Below is some correspondence between Isaac Park and myself.  Isaac is working on phenological issues with Redbud and thanks go to Nancy Cowden for making that connection.  Isaac is now on the list so will be getting any further correspondence....my reply to Isaac follows his post....


      More black than ash-buds in the front of March.
        --Al Tennyson

      > Dear Dr. Droege,
      > I got Dr. Cowden's email regarding the examination of using redbud
      > set to examine pollinator success as regards floral timing, and it
      > like an interesting idea, and wouldn't take too much effort to add
      > during data collection.  In addition, it seems to be somewhat
      common to
      > have both fruiting and flowering collections of the same plant (or
      > least plants from the same location) within the same year, which might
      > allow an examination of flowering timing vs. seed set, which could
      > used to estimate pollination activity (assuming that pollination is
      > primary limiter of seed set for /Cercis/).  I'm not quite sure
      how the
      > data would be interpreted, though, as the records will have a lot
      > spatial and temporal gaps, and in many cases there may not be flowering
      > samples collected from the same location and year as fruiting samples.
      > It might be possible to use the floral timing of other species, such
      > flowering dogwood, which allows more accurate estimation of flowering
      > onset, as a proxy for general spring timing, and correlate that to
      > set.  In some cases, it might even be possible to correlate seed
      > success to satellite-based estimates of spring phenology.
      > There are still several unknowns, but it seems like an interesting
      > to look at, and I'd love to examine some of the ecological effects
      > phenological timing.  I'll be driving back from South Carolina
      > Milwaukee on the 26th, so I may not have email access for a few days,
      > but if you drop me a line, I'd love to talk to you about this once
      I get
      > up there.
      > Thanks,
      > Isaac Park
      > UW-Milwaukee
      > Dept. of Geography
      > 410 Barton Hall
      > Milwaukee, WI 53204
      >> Hello Isaac:
      > Good to hear from you and a very interesting point you brought up,
      > that I had not even considered....that there are historic collections
      > that could be investigated almost immediately.  I would love
      to talk
      > to you more about this so when you get back to the University give
      > a shout at the numbers below, but note that I will be out of the
      > office for about 10 days starting next week.
      > I think we are coming from different angles on this problem, but one
      > that could be very compatible.
      > So here are some summary thoughts regarding possible directions
      > investigations could go.
      > 1.  Historic collections hold promise to look at changes over
      > geographic location, habitat and phenological measurements of
      >  earliness or lateness in Cercis seed set.
      > 2.  Since Cercis it is a highly bee centric plant, most of the
      > pollination could be assumed to come from bees.
      > 3.  Is Cercis self incompatible?  Would that be a problem
      in looking
      > at specimens that are relatively isolated...such as in the suburbs?
      > 4.  Could a net work of citizens be set up who would take photographs
      > of seed pods (particularly in the green translucent phase) that could
      > be used to estimate seed set over the same independent variables as
      > point #1?
      > 5.  How tight is the relationship between bee visitation and
      seed set?
      > 6.  What other factors could impact the numbers of seeds per
      pod and
      > the number of missing seeds?  
      > 7.  Could bee collections from this plant be easily made and
      > that be very illuminating?

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