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47Re: [beemonitoring] Bombus-GroundIvy Connection?

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  • Thomas of Baltimore
    Dec 21, 2006
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      What percentage of the world's extant flowering plant species have evolved flower arrangements that are pollinated by only a specific group of pollinating insects?
      If specialist flower/specialist pollinator relationships are as rare as I expect, then it would seem the remaining plants have in varying degrees evolved flowers under the selective pressure of pollinators which favor it (for example, Ground Ivy & Bumblebees). But Ground Ivy and Bombus are not one of the specialist flower/specialist pollinator relationships as evidenced by the variety of U.S. insects reported to visit its blooms.  
      I am suggesting that over time the Glechoma hederacea flower was in part "shaped" by its long-term association with British (and European) Bombus spp.  If that is true, then the shape of the Ground Ivy flower that we see today reflects this relationship.  In a sense, we can "read" that relationship in the flower's design.  But, we also know that it is used by non-bombus species so either the design of the Ground Ivy flower leaves room for the other pollinator species, or the other pollinator species have influenced the flower design we see.
      Either way, it serves the Ground Ivy to maintain some pollinator access wiggle room in case the Bumblebee(s) have a bad year or worse disappear altogether.
      Why do I care?  Well, as Dr. Inouye suggested the introduction of a non-native flower into an ecosystem could impact other flowering plants nearby if native pollinators prefer the non-native flower over the native flower.  My line of questioning attempts to implicate the native pollinators, at least in part, to the successful naturalization of some non-native flower species.
      Learning more about what "role" that native species play in the spread of non-native species is important because it reframes the conversation away from the highly-charged and vague, but thoroughly unscientific terminology like "alien" and "invasive".  By asking, what if the native Bombus prefer Ground Ivy because the Ground Ivy's flower evolved to serve Bombus better, we shift away from looking for a one-sized-fits-all diagnostic that explains the how and why of each and every successful species introduction-naturalization. 
      In the background is an unexamined bias against "non-native" species.  If anything points to a bias against "non-native" species it is that the "non-native container" is so poorly defined and vague that anything can be placed into it or removed at will. 
      In this model, the non-native wheat is ok, but Ground Ivy is not. 
      There are many apples and oranges to be sorted out, too.  How shameful that the science community allows the Chestnut Blight, Siberian Elm, and the Starling to be lumped into a group together!   The most dangerous result of this "lumping" iwould be attempts to fashion one-size-fits-all responses to dealing with them (ie, eradication, chemicals/poisons, propaganda).   
      Consider this:  Not long ago, the New England population of the Baltimore Checkerspot butterfly "discovered" that Plantago lanceolata contains the same chemicals needed for its larvae to develop.  By adding the Plantain to its menu, the New England Baltimore Checkerspot's population is expanding for the first time. 
      In contrast the Mid-Atlantic population of Baltimore Checkerspots has not adopted Plantain so Maryland's state insect (which I've never seen in person) continues to decline in this area along with its wetland habitat.
      With that in mind, is wholesale and wanton eradication of the non-native P. laceolata still called for?  Or, does the emergent Baltimore Checkerspot-P. lanceolata ecological association demonstrates how far along Plantago has integrated into the environment.  (By integrate I mean the constellation of ecological associations formed between Plantago and other New England lifeforms since it arrived.)   How many micro-associations between Plantago and other species have taken place which are not as easily noticed as the Checkerspot-Plantago relationship?

      On 12/21/06, David Inouye <inouye@...> wrote:

      That's interesting that bees of all those proboscis lengths will use the same flower.  Quantitative data on frequency of use by each of those species would be interesting. Bumble bees will investigate a wide range of flowers, in my experience, but typically settle quickly on those that are a good morphological match and rewarding.

      The 5.8mm measurement for terrestris/lucorum sounds short to me.  I've seen data reporting them as about 8 mm, which then puts them in a different category from honey bees.

      At 02:13 PM 12/21/2006, you wrote:

      According to the British bumbleebee researcher I contacted, (at least) four true British Bumblebee species are known to visit Glechoma hederacea; Bombus pascuorum (most frequent), B.lucorum , B.pratorum , and B.hortorum. 
      Each of the four British species are listed in the "tongue length" table below.  Dr Inuoye suggested a correlation between Bombus proboscis length and use of G. hederacea.  Is that corroborated by the data I provided?
      Average tongue lengths mesured from foraging bumblebee workers.
      Tongue length mm
      Bombus hortorum
      Bombus lapidarius
      Bombus pascuorum
      Bombus pratorum
      Bombus terrestris/lucorum

      (Table source: http://www.bumblebee.org/bodyTongue.htm)

      On 12/19/06, David Inouye <inouye@...> wrote:

      At 04:45 PM 12/19/2006, you wrote:

      >Background 1: In my Baltimore City neighborhood, and in many urban
      >areas, Ground Ivy (Glechoma hederacea) is now one of the most
      >important flowers for bumblebees in part because of its early season
      >bloom and because of its vast abundance and wide distribution.
      >Question 1: Before Europeans arrived, while the indigenous people
      >were "managing" the landscape, what early season flower species did
      >the native bumblebee spp depend on?

      Depends on their proboscis length.

      >Background 2: (a) Wikipedia says, "In Britain, until relatively
      >recently, 19 species of native true bumblebee were recognised..."
      >(b) The Wisconsin Bumblebee regional chart lists 4 species native to Maryland.
      >Question 2a: If Ground Ivy evolved in close relationship with
      >British bombus species, then the Ground Ivy we see today may be the
      >result of the selective pressure of associating with up to 19
      >bumblebee species? Wouldn't that make Ground Ivy a super bumblebee flower?

      It is unlikely that all 19 species would have foraged on a single
      plant species. The relationship between bees and plants is typically
      mediated by an appropriate match between proboscis length and corolla
      tube length, so probably only one subset of the three categories of
      proboscis length would have visited the flowers.

      >Question 2b: So now consider the possibility that our native North
      >American bombus species also prefers Glechoma hederacea because it
      >is a super bombus food. What impact on the distribution of Ground
      >Ivy would result from this preference by our native bombus
      >spp? Would an adopted preference for Ground Ivy by N.A. bombus spp
      >impact any other native/non-native early spring flowering plants
      >which may be blooming in the vicinity? And if so, in what way(s)?
      I suspect this plant is not limited by seed production and dispersal,
      so the effects of native Bombus on the introduced plant are probably
      minimal. There probably is the potential for ground ivy to have a
      negative impact on visitation to (and thereby seed set of) some
      native plants that flower at the same time.

      Dr. David W. Inouye, Director
      Graduate Program in Sustainable Development and
      Conservation Biology
      Room 1201, Biology/Psychology Building
      University of Maryland
      College Park, MD 20742-4415
      FAX 301-314-9358

      For the CONS home page, go to http://www.umd.edu/CONS

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