Changes in the Wild Bee Fauna of Rockefeller Prairie
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Changes in Wild Bee Fauna Changes in the Wild Bee Fauna of Rockefeller Prairie JENNIFER L. HOPWOOD1, 2 University of Kansas, Lawrence, KS 66045 1 Present address: Midwest Pollinator Outreach Coordinator, The Xerces Society for Invertebrate Conservation, PO Box 229, St Louis MO 63166 2 [email protected] Abstract: Bees are considered to be the most important pollinators in most ecosystems, including tallgrass prairie. While recent research highlights the possibility of a global decline in pollinators, the lack of baseline data, species lists and well-documented collections of pollinators for many localities makes assessing anthropogenic impacts difficult. However, wild bees were sampled in 1978 at Rockefeller Prairie near Lawrence, Kansas, which provides one useful source of baseline data. Management of Rockefeller Prairie, a small but high quality prairie remnant, has been consistent since the 1978 collection. The land surrounding Rockefeller Prairie has undergone minor changes (different agricultural practices, secondary succession). The goal of this study was to revisit Rockefeller Prairie to make comparisons between the past and current bee fauna. I re-sampled the site by collecting bees from flower species previously sampled in 1978, as well as other flower species not previously sampled. I also employed pan traps, a more recent passive method of collection. Pan traps are colored plastic bowls filled with soapy water that attract flower-visiting insects. I found little overlap between my collection and the bee communities of the past collection. The species composition of my sample was markedly different from past samples, with 24 bee species previously found in Rockefeller Prairie in 1978 that were not recollected in 2004. Most notably missing from the 2004 collection was the most abundant bee in the previous collection, Bombus pensylvanicus, a species that has become less widespread across the Eastern United States in recent years. Proceedings of the North American Prairie Conference 21:139-145 Keywords: bees, Bombus pensylvanicus, pollinator ecology, prairie forbs, re-sampling. Introduction 2000). Honey bees (Apis mellifera) contribute Animal pollinators are integral to the life history about $14.6 billion in crop pollination each year in of many flowering plants, providing an essential the United States (Morse and Calderone 2000) and wild bee species contribute $3.07 billion to fruit and ecosystem service in both natural plant communities vegetable pollination (Losey and Vaughan 2006). and agricultural ecosystems. Bees are considered Suitable bee habitat must include a diversity of to be the most important group of pollinators, flowering species and nesting substrates, because possessing structural and behavioral adaptations bees have a wide range of specialized floral and that enable them to pollinate a wide variety of plants nesting requirements. Bees of both sexes may successfully (Delaplane and Mayer 2000, Michener exploit many floral species for nectar, and females of 2000). Bees are important in the maintenance of social species and some solitary species also utilize diversity in wild flowers (Kearns et al. 1998), in the a diversity of forbs for pollen. Female bees of other conservation of threatened plant species (Sipes and solitary species are oligolectic, visiting only one or Tepedino 1995), and in the reproduction of numerous several closely related flowering species for their agricultural crop species (Delaplane and Mayer specialized pollen needs (Wcislo and Cane 1996). Proceedings of the 21st North American Prairie Conference (2010) 139 Prairie Entomology and Zoology The nesting preferences of bees are highly more than 200 plant species, including the federally variable, and while many species dig subterranean endangered Mead’s milkweed (Asclepias meadii) nests in their preferred location and soil type, some and Western prairie fringed orchid (Platanthera species nest above ground in plant stems or dead praeclara) (K. Kindscher, pers. comm.). From the wood, or may need specific nest-building materials 1870’s until 1956, Rockefeller Prairie was maintained such as mud, snail shells or resin (Linsley 1958). by annual mowing for hay, and subsequent burning Prairies, which provide a diversity of flowering of the remaining stubble (Kindscher 1992). The species and nesting substrates, can be suitable habitat University of Kansas acquired the land in 1956 and for bees. the prairie was burned every three years until the Globally, researchers have begun to suspect an late 1960’s, when woody plants from the nearby impending pollination crisis in both natural and native oak-hickory forest bordering a portion of the agricultural ecosystems, due to potential declines in prairie began invading. Since that time, the prairie pollinator populations (Buchmann and Nabhan 1996, has been burned in one to two year intervals, and Allen-Wardell et al. 1998). Habitat fragmentation, most recently (1986 onwards) has been burned invasive plant and animal species, and extensive in the spring every other year (Kettle et al. 2000). usage of herbicides and pesticides have been Rockefeller Prairie was burned prior to this study in identified as some of the key threats that pollinators the spring of 2004. As it was in 1978, Rockefeller face (Allen-Wardell et al. 1998, Kearns et al. 1998). Prairie remains bordered by forest, cultivated fields, Losses of wild bees have been documented in some open secondary vegetation and prairie restoration regions of the world (Williams 1982, Biesmeijer et (Kettle et al. 2000), although in the interim between al. 2006), with declines suspected elsewhere (NRC 1978 and 2004, different agricultural practices were 2007). employed, and secondary succession progressed in While the influence of humans on flora and non-cultivated areas. fauna is of considerable interest, it can be difficult to document anthropogenic impacts because detailed Bee sampling historic data from specific localities are rare. The lack During the 1978 study, Laroca sampled bees of baseline data, species lists and well-documented Table 1. List of Prairie Forbs sampled for bees. collections of pollinators for many localities make historic and contemporary comparisons difficult Common name Scientific name (Marlin and LaBerge 2001, NRC 2007). One valuable source of baseline collections was made Lead plant Amorpha canescens near Lawrence, Kansas, U. S. A. by Sebastio Laroca Partridge pea Chamaecrista fasciculata Sumac Rhus glabra* (1983), then a doctoral student at the University of Purple prairie clover Dalea purpurea Kansas. Laroca’s study area included a high quality Pale purple coneflower Echinacea pallida tallgrass prairie remnant, Rockefeller Prairie. I Gray-headed coneflower Ratibida pinnata revisited Laroca’s study in 2004 to re-sample the Mountain mint Pycnanthemum tenuifolium bees to assess changes in abundance and bee species Black-eyed susan Rudbeckia hirta richness after 26 years. A high degree of similarity Compass plant Silphium laciniatum between samples from Rockefeller Prairie in 1978 Indian hemp dogbane Apocynum cannabinum** Butterfly milkweed Asclepias tuberosa** and 2004 was expected, as the management of the Blue sage Salvia azurea** prairie preserve remained consistent. Stiff tickseed Coreopsis palmata** Tall boneset Eupatorium altissimum** Methods Canada goldenrod Solidago canadensis** Study site Rattlesnake master Eryngium yuccifolium** Rockefeller Prairie is a 4.6-hectare native tallgrass * denotes flowers sampled only in 1978; prairie located within the Rockefeller Experimental ** denotes flowers sampled only in 2004 Tract in Jefferson County, Kansas. The prairie has 140 Proceedings of the 21st North American Prairie Conference (2010) Changes in Wild Bee Fauna in Rockefeller Prairie by collecting for one hour on seven sampling dates from June to August in Table 2. Bee species collected at Rockefeller Prairie in 1978 and 2004. 1978 (Laroca 1983). Bees were re-collected at Rockefeller on seven sampling dates from June Family Bee species through September in 2004. I sampled in 2004 using Colletidae * Colletes latitarsus an aerial net to collect bees off blooming flowers for ** Hylaeus affinis one hour on each sample date. Hylaeus modestus Andrenidae Andrena helianthi In both 1978 and 2004, bees were only sampled Perdita ignota on days with warm temperatures (above 70ºF), Halictidae * Augochlora pura abundant sun (less than 50% cloud cover), and calm Augochloropsis metallica winds (less than 5 m/s). In 1978, Laroca sampled ** Augochlorella aurata bees from nine species of prairie flowers, a subset of ** Halictus ligatus * Halictus parallelus prairie forbs (Table 1). Lasioglossum bruneri In 2004, I swept bees off all prairie flowers in * Lasioglossum rowheri bloom, but made a distinct effort to sweep bees from Lasioglossum obscurum the forb species Laroca had previously sampled * Lasioglossum imitatum (with the exception of sumac, which does not bloom ** Lasioglossum coreopsis * Lasioglossum disparile in the season following a burn). Pan traps were * Lasioglossum nr oblongum also implemented to supplement the collection of * Lasioglossum nr paradmirandum bees. Pan traps are colored plastic bowls filled with Lasioglossum tegulare water and unscented dish soap, and bees attracted Lasioglossum versatum to the color hit the water and drown. Six colors of * Lasioglossum sp. A Nomia bakeri pan traps, light blue, dark blue, fluorescent blue, * Sphecodes sp. A fluorescent yellow, yellow and white, were used in Megachilidae