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Why Didn't I Think of That?

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  • Peter Bernhardt
    Dear Colleagues: The attached paper describes how you can turn an American slipper orchid flower (Cypripedium) into a pan trap for bees. I reviewed the
    Message 1 of 1 , May 5, 2009
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      Dear Colleagues:

      The attached paper describes how you can turn an American slipper orchid flower (Cypripedium) into a pan trap for bees.  I reviewed the manuscript for the journal several months ago and kept asking myself "Why didn't I think of that myself."  You can go nuts trying to find the appropriate time of day when bees visit lady's slipper orchids but this technique allows you to "set the trap" and then return later to see what you've caught.  Some lady's slippers are good place to look for bees that died of exposure when they couldn't escape the pouch overnight.  In Oregon, Dr. Nan Vance and I found that the pouches of Cypripedium montanum can become fatal dungeons for Osmia and some Megachile sp. (their heads may be too large to fit through the rear escape hatches in the flower.

      Peter Bernhardt

      ---------- Forwarded message ----------
      From: Peter Bernhardt <bernhap2@...>
      Date: Tue, May 5, 2009 at 8:56 AM
      Subject: Fwd: FW: Enhancing the trap of lady's slippers: a new technique for discovering pollinators yields new data from Cypripedium parviflorum (Orchidaceae)
      To: luoyibo <luoyb@...>




      ---------- Forwarded message ----------
      From: Peter Bernhardt <bernhap2@...>
      Date: Mon, May 4, 2009 at 9:30 AM
      Subject: Fwd: FW: Enhancing the trap of lady's slippers: a new technique for discovering pollinators yields new data from Cypripedium parviflorum (Orchidaceae)
      To: Retha Meier <rmeier3@...>


      Dear Luo:

      I reviewed this manuscript for the journal.  Perhaps we should try this to trap more pollinators of Cypripedium if we suspect thaqt some visitors are nocturnal?  What do you think?  That is, put a ribbon under the escape holes before we go home in the vening.  That way we can see if it receivespollinators at night or before dawn.

      Peter

      ---------- Forwarded message ----------
      From: Peter Raven <Peter.Raven@...>
      Date: Fri, May 1, 2009 at 10:41 PM
      Subject: FW: Enhancing the trap of lady's slippers: a new technique for discovering pollinators yields new data from Cypripedium parviflorum (Orchidaceae)
      To: Peter Bernhardt <bernhap2@...>


      ????????????

       


      From: Neal Smith [mailto:smithn@...]
      Sent: Friday, May 01, 2009 6:21 PM
      To: Smithn@...
      Subject: Enhancing the trap of lady's slippers: a new technique for discovering pollinators yields new data from Cypripedium parviflorum (Orchidaceae)

       

       

       

       

      Botanical Journal of the Linnean Society

      Volume 160, Issue 1, Pages 1-10

      Published Online: 16 Apr 2009

       

       

         

         

       

       

       

      Enhancing the trap of lady's slippers: a new technique for discovering pollinators yields new data from Cypripedium parviflorum (Orchidaceae)

      MARTHA A. CASE* and ZACHARY R. BRADFORD

      Biology Department, College of William & Mary, Williamsburg, VA 23187, USA

      Correspondence to   *E-mail: macase@...

       

      KEYWORDS

      Andrena • Cypripedioideae • food deceptive • Hymenoptera • orchid • pollination • ribbon • solitary bees

      ABSTRACT

            

       

      Approximately one-third of orchid species offer no reward to their floral visitors and instead trick them into pollination. Typically, these deceptive systems have low visitation and fruiting rates because pollinators can learn to avoid non-rewarding species. Consequently, pollination ecology studies in these species often require long hours in the field to witness relatively few floral visitations relative to rewarding plants. Cypripedium parviflorum is a food-deceptive orchid with a pouch-like trap that temporarily imprisons pollinators. To escape, pollinators exert pressure on the stigma which facilitates pollination and widens the escape holes located near each anther. This study reports the use of a ribbon and clip to block the escape passageway of this species in order to retain and observe visiting insects. The device was tested in a large population and was shown to increase significantly the probability of observing floral visitors by nearly three-fold. Ten species of hymenopteran visitors in the families Andrenidae, Apidae, Halictidae and Megachilidae were observed, with two female Adrena tridens and one male Adrena perplexa successfully removing pollen. Insect visitation to the orchids occurred during the first half of the flowering period and was significantly associated with warm, clear days. 

       

       

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      INTRODUCTION

            

       

      The bizarre and complex pollination ecology of the orchid family (Orchidaceae) has fascinated naturalists for over 100 years (Darwin, 1862; van der Pijl & Dodson, 1966; van der Cingel, 2001). Particularly intriguing is the fact that nearly one-third of orchid species offer no apparent reward to their pollinators, instead tricking them into pollination by offering a bogus reward, such as food or sex (Schiestl, 2005). Some researchers have suggested that pollination by deceit is one of the key elements in understanding the floral and species diversity of the family (Cozzolino & Widmer, 2005).

       

      Despite the long-standing interest in the potential for pollinators to contribute to the reproductive isolation of plant populations, the evolutionary mechanisms in operation are still poorly understood (Nilsson, 1992; Waser, 1998; Tremblay et al., 2005; Peakall, 2007). One factor that is critical for understanding how plants respond to pollinator selection pressures is the ability to observe floral visitation and to identify pollinators. Deceptive orchids, however, can be particularly problematic for studies in pollination ecology because insects can learn to avoid additional encounters with non-rewarding plants (Heinrich, 1975; Dafni, 1984; Nilsson, 1992; Cozzolino et al., 2005; Internicola et al., 2006). This often leads to lower visitation rates and fruit production (Nilsson, 1992; Peakall & Beattie, 1996; O'Connell & Johnston, 1998; Bänziger, Sun & Luo, 2005; Tremblay et al., 2005; Jersáková, Johnson & Kindlmann, 2006; Jersákováet al., 2008) and reduces the likelihood of observing pollination and identifying pollinators.

       

      With few exceptions, such as self-pollinating species, the slipper orchids (subfamily Cypripedioideae) are food-deceptive orchids that attract adult insects that are seeking food for themselves or a brood-place for larvae (Pridgeon et al., 1999). In this subfamily, the highly modified petal (the labellum) is modified into an inflated pouch with an entrance orifice and two basal escape orifices, each partially occluded by an anther (Fig. 1A). Visitors enter the labellum through the large entrance orifice and, if they are the right size and shape to be pollinators, they have difficulty escaping out of the entrance. Usually not more than 10 min after imprisonment (Nilsson, 1979), pollinators crawl beneath and press up against the stigma. This action transfers any pollen they may be carrying to the stigmatic surface and gives them leverage to widen the exit hole (Nilsson, 1979). Subsequently, the insect squeezes out of one of the two exit holes, picking up a new mass of pollen. For pollination to occur, a pollinator must be tricked into entering and correctly exiting at least two flowers.

       

      Like other deceptive orchids (for example, Peakall & Beattie, 1996), pollination studies in the genus Cypripedium L. frequently require many hours in the field to witness pollination or even to find insects trapped in the labellum. For example, Li et al. (2006) required 47.5 h of observation and two field seasons to observe five pollinators enter the labella of C. tibeticum King ex Rolfe. The problem of infrequent observations is compounded by the common occurrences of sparsely populated or relatively small Cypripedium populations (as in many North American sites) and dense but often inaccessible populations in China (where two-thirds of known Cypripedium species occur; Bänziger et al., 2005). Together, these factors have undoubtedly contributed to a dearth of data on Cypripedium pollination. For only nine of approximately 45 Cypripedium species have pollinators been studied (Bänziger, Sun & Luo, 2008). Virtually all studies in the genus have required extensive observation times, dense clumps of flowers to monitor or large sample sizes of flowers to obtain pollinator data (for example, Stoutamire, 1967; Nilsson, 1979; Catling & Knerer, 1980; Sugiura et al., 2001; Bänziger et al., 2005, 2008; Herring, 2007; Li et al., 2008). To help combat the difficulties associated with pollination studies in Cypripedium, the major goals of the present study were: (1) to develop a field method that would increase the chances of observing visitors and pollinators of lady's slipper orchids; (2) to apply the method to C. parviflorum Salisb. var. pubescens (Willd.) Knight; and (3) to analyse the capture data for insight into climatic conditions that could lead to a better prediction of pollinator activity. These objectives were met by designing a system that modifies the trapping device of the flower. This system retains potential pollinators in the labellum until the experimenter observes the insect and allows it to complete the pollination process. With the increase in captured visitors caused by the trapping device, sample sizes were large enough to permit a statistical analysis that correlated climatological variables with insect visitation.

       

       


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