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Re: [beemonitoring] Divining the floristic record of Bee Specimens

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  • Peter Bernhardt
    Dear Colleagues: Dr. Neff is taking us into a sensitive area. The fact remains that the majority of American pollination biologists still refuse to identify
    Message 1 of 7 , Feb 9, 2010
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      Dear Colleagues:

      Dr. Neff is taking us into a sensitive area.  The fact remains that the majority of American pollination biologists still refuse to identify the pollen grains carried by the insects they catch on flowers.  This leads to the premature conclusion that, "if I catch the insect in a flower, then that insect must be a pollinator or at least a potential/prospective pollinator of the flowers of that species."  Throughout the 20th century, and into the 21st, an entire "branch" of pollination ecology has been built on the notion that field notes and insect collections made in Illinois during the 1920's represent the Shining Path to pollinator identification/conservation.    

      It's a shame that relatively simple techniques of pollen identification instituted by the Australian Tarlton Rayment and the late Walter Macior are not used more often.  Yes, the grains of a broad number of North American plants are often very difficult to identify but the trick is to make a reference library of pollen slides from known plants before you harvest and identify pollen carried by insects.  It's still the best way as there are few pollen atlases published of any region.  Some grains are real signature grains and can't be mistaken for anything else provided you have the library to back you up.  This includes grains released as polyads or tetrads and those with prominently sculptured surfaces and apertures (pores and/or slits).  That's why you can easily identify both the fossil and living pollens of members of the WInteraceae.  Even look alike grains can betray their identity by their different sizes and the color and density of lipid droplets clinging to the pollen wall.  One of my graduate students found this a useful technique for separating pollen of the Rosaceae (Potentilla, Fragaria, Rosa etc.) found on the same bee at the same site.  The grains of North American Paeonia spp. are not very memorable either until you realize that their anthers release an unprecedented number of sterile collapsed grains (30-50%) and that's another signature in it's own way.  If you keep a library you may even be able to identify grains of two different species that belong to the same plant genus found on the same insect (see my past coauthored papers on Acacia and Persoonia). 

      One of the wash-the-pollen-off-the-insect, dry-the-residue and stain-the- residue techniques in the books mentioned by Dr. Neff is my technique.  That is, I modified pre-existing techniques learned in the lab of Bruce Knox at the U. of Melbourne from 1977-1985.  If I could do it all over again, though, I'd rewrite one aspect of those techniques.  I know now to never, never never wash pollen off an insect using ethanol.  You destroy the insect's cuticle and shorten the "useful life" of the pinned voucher specimen.  These days I wash pollen of insects using ethyl acetate.  Do this procedure in a fume hood, of course.

      Just remember that most pinned insect specimens came out of a communal killing jar.  The corpses bumped and clumped together so the presence of a few rose pollen grains on a bumblebee doesn't mean it every visited a rose in its life.  Something else in the jar may have foraged on that rose on that same day.  It's up to you to decide how many grains derived from a corpse amount to significant and sustained rates of foraging.  Wash your jars with soap and hot water and keep forceps and nets as clean as possible in-between usage.

      Sincerely, Peter I'm-still-washing-beetles Bernhardt         

      On Tue, Feb 9, 2010 at 10:13 AM, Jack Neff <jlnatctmi@...> wrote:
       

      All:  I would not be so negative about analyzing past dietary patterns from old pollen, at least for local faunas.  Extracting pollen from pinned specimens is easy (assuming they haven't been subjected to the current fad for specimen washing) and there are several methods available from the literature (Dafni et al, 2005; Kearns and Inouye, 1993).  Many pollens are quite distinctive and can be identified without any special preparation beyond staining, at least if one knows the local possibilities.  More nondescript pollen may require acetolysis, a nasty involved process.  SEM works exceedingly well but can be expensive if your institution does not have its own machine.  The key is having a good local reference collection for comparison purposes.  Identifying pollen from samples from across a broad area (the entire Great Plains) is much more problematic.   Identifying unknown pollens from an unknown flora can be extremely frustrating for the non-palynologist, and often isn't a snap even for the professional.

      best

      Jack


      John L. Neff
      Central Texas Melittological Institute
      7307 Running Rope
      Austin,TX 78731 USA
      512-345-7219



      From: "RestoreHabitat@..." <RestoreHabitat@...>
      To: beemonitoring@yahoogroups.com
      Sent: Mon, February 8, 2010 8:15:28 PM
      Subject: Re: [beemonitoring] Divining the floristic record of Bee Specimens

       

       
       
      To All
                 
                  The subject of bee phenology and Redbud is an excellent introduction to two questions, the answers for which I am seeking some assistance:
      • First question:  Would sampling of native bee specimens collected historically have the potential to reveal the species of pollen (and, therefore, the flora) from which they themselves were collecting when they were collected? I am not sufficiently familiar with methods of specimen collection to know if, historically, collection of species entailed netting and pinning but little else that would eliminate the pollen record that the specimen contained. Obviously, washed bees would not contain the information that I am seeking. My research to support restoration efforts has revealed substantial declines in nectar and pollen producing flora native to this region and to which our native pollinators are so well adapted.
      • That leads to the second question:  Has there been observed a measurable decline in the size of adult native bees (Bombus is a good example) during certain portions of their pollen and nectar gathering season over the past few decades? Recently, field observations have shown a remarkable decrease in the size of workers toward the end of the season. Does anyone have any information or guidance on data that would indicate whether this is typical, as observed historically; or, perhaps, a more modern development?
               These data will assist in creating a comprehensive plan for restoration of heliophilic habitat that will support the greatest diversity of both native floral and fauna.
       
                      Randy Pheobus, President
                          Native Grassland Conservancy
                              301-440-8915
                  


    • Doug Yanega
      ... Do you have either a simple summary, or links to online copies, of either or both of the techniques you mention? Perhaps more to the point, though, is the
      Message 2 of 7 , Feb 9, 2010
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        Peter Bernhardt wrote:

        >It's a shame that relatively simple techniques of pollen
        >identification instituted by the Australian Tarlton Rayment and the
        >late Walter Macior are not used more often. [snip]
        >
        >One of the wash-the-pollen-off-the-insect, dry-the-residue and
        >stain-the- residue techniques in the books mentioned by Dr. Neff is
        >my technique. That is, I modified pre-existing techniques learned
        >in the lab of Bruce Knox at the U. of Melbourne from 1977-1985. If
        >I could do it all over again, though, I'd rewrite one aspect of
        >those techniques. I know now to never, never never wash pollen off
        >an insect using ethanol. You destroy the insect's cuticle and
        >shorten the "useful life" of the pinned voucher specimen. These
        >days I wash pollen of insects using ethyl acetate. Do this
        >procedure in a fume hood, of course.

        Do you have either a simple summary, or links to online copies, of
        either or both of the techniques you mention? Perhaps more to the
        point, though, is the question as to why any washes need to be used
        at all?

        We have at least 80,000 old pinned bee specimens in our collection
        with scopal loads, and washing them individually, drying the residue
        individually, and staining the residue individually, is vastly more
        manpower-intensive than we could ever hope to manage, even if we had
        a source of outside funding. The number of samples even a full-time
        technician could process and ID per day is probably too low to be
        cost-effective, even if that technique itself is *materially* cheap.
        The wear and tear on the bee specimens and their labels is also VERY
        significant, and that alone would probably prevent us from even
        *attempting* such a project.

        So, for the kind of large-scale processing we would need, we would
        also need a highly streamlined procedure which requires minimal
        specimen handling. With that in mind, let me ask: would it be
        possible to place a very tiny droplet of some prepared medium on a
        slide, scrape pollen grains out of the scopa directly into this
        medium under a microscope, and drop a cover slip on it and be ready
        to go?

        If so, it would eliminate at least four or five time-consuming steps
        (the worst of them being having to strip all the labels off the pin
        in order to wash the specimen - and note that ethyl acetate can
        destroy pin heads! Morpho brand pins are especially vulnerable to
        this). This would still entail *some* wear and tear on the specimens
        - many hind legs would be snapped off - but this would be *orders of
        magnitude* less damage than the washing would cause, on specimens and
        labels 50+ years old.

        What do you think?

        Peace,
        --

        Doug Yanega Dept. of Entomology Entomology Research Museum
        Univ. of California, Riverside, CA 92521-0314 skype: dyanega
        phone: (951) 827-4315 (standard disclaimer: opinions are mine, not UCR's)
        http://cache.ucr.edu/~heraty/yanega.html
        "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82
      • Jack Neff
        Doug et al. I take it you want to analyze what pollen bees are actively collecting (scopal pollen) rather than some crude record of what they may, or may not,
        Message 3 of 7 , Feb 9, 2010
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          Doug et al.

          I take it you want to analyze what pollen bees are actively collecting (scopal pollen) rather than some crude record of what they may, or may not, have visited (overall body pollen).  The latter is extremely important for  pollination studies but not so much for bee diet.  For the former, I heartily recommend the scrape-some-scopal pollen-onto-a-slide method (perhaps with some melted stained glycerin jelly).  Much quicker and less destructive than washes which unnecessarily combine pollen from different parts of the body.  If the first try doesn't yield anything readily identifiable, one can always go back to the scopa for another sample which may need further processing.

          best

          Jack


          John L. Neff
          Central Texas Melittological Institute
          7307 Running Rope
          Austin,TX 78731 USA
          512-345-7219



          From: Doug Yanega <dyanega@...>
          To: beemonitoring@yahoogroups.com
          Sent: Tue, February 9, 2010 12:32:38 PM
          Subject: Re: [beemonitoring] Divining the floristic record of Bee Specimens

           

          Peter Bernhardt wrote:

          >It's a shame that relatively simple techniques of pollen
          >identification instituted by the Australian Tarlton Rayment and the
          >late Walter Macior are not used more often. [snip]
          >
          >One of the wash-the-pollen- off-the-insect, dry-the-residue and
          >stain-the- residue techniques in the books mentioned by Dr. Neff is
          >my technique. That is, I modified pre-existing techniques learned
          >in the lab of Bruce Knox at the U. of Melbourne from 1977-1985. If
          >I could do it all over again, though, I'd rewrite one aspect of
          >those techniques. I know now to never, never never wash pollen off
          >an insect using ethanol. You destroy the insect's cuticle and
          >shorten the "useful life" of the pinned voucher specimen. These
          >days I wash pollen of insects using ethyl acetate. Do this
          >procedure in a fume hood, of course.

          Do you have either a simple summary, or links to online copies, of
          either or both of the techniques you mention? Perhaps more to the
          point, though, is the question as to why any washes need to be used
          at all?

          We have at least 80,000 old pinned bee specimens in our collection
          with scopal loads, and washing them individually, drying the residue
          individually, and staining the residue individually, is vastly more
          manpower-intensive than we could ever hope to manage, even if we had
          a source of outside funding. The number of samples even a full-time
          technician could process and ID per day is probably too low to be
          cost-effective, even if that technique itself is *materially* cheap.
          The wear and tear on the bee specimens and their labels is also VERY
          significant, and that alone would probably prevent us from even
          *attempting* such a project.

          So, for the kind of large-scale processing we would need, we would
          also need a highly streamlined procedure which requires minimal
          specimen handling. With that in mind, let me ask: would it be
          possible to place a very tiny droplet of some prepared medium on a
          slide, scrape pollen grains out of the scopa directly into this
          medium under a microscope, and drop a cover slip on it and be ready
          to go?

          If so, it would eliminate at least four or five time-consuming steps
          (the worst of them being having to strip all the labels off the pin
          in order to wash the specimen - and note that ethyl acetate can
          destroy pin heads! Morpho brand pins are especially vulnerable to
          this). This would still entail *some* wear and tear on the specimens
          - many hind legs would be snapped off - but this would be *orders of
          magnitude* less damage than the washing would cause, on specimens and
          labels 50+ years old.

          What do you think?

          Peace,
          --

          Doug Yanega Dept. of Entomology Entomology Research Museum
          Univ. of California, Riverside, CA 92521-0314 skype: dyanega
          phone: (951) 827-4315 (standard disclaimer: opinions are mine, not UCR's)
          http://cache. ucr.edu/~ heraty/yanega. html
          "There are some enterprises in which a careful disorderliness
          is the true method" - Herman Melville, Moby Dick, Chap. 82


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