The Canadian Field-Naturalist

Volume 125, Number 4 October –December 2 011

Bees and Butterflies in Burned and Unburned Alvar Woodland: Evidence for the Importance of Postfire Succession to Insect Pollinator Diversity in an Imperiled Ecosystem

ALANA N. T AYLOR 1 and PAUL M. C ATLING 2

1York University, 4700 Keele Street, Toronto, Ontario, M3P 1J3 Canada; email: [email protected] 2Agriculture and Agri-Food Canada, Environmental Health, Biodiversity, Wm. Saunders Bldg., Central Experimental Farm, Ottawa, Ontario, K1A 0C6 Canada; email: [email protected]

Taylor, Alana N. and Paul M. Catling. 2011. Bees and butterflies in burned and unburned alvar woodland: Evidence for the importance of postfire succession to insect pollinator diversity in an imperiled ecosystem. Canadian Field-Naturalist 125(4): 297-306. The apparent importance of successional habitat to pollinating insects, specifically bees (Hymenoptera) and butterflies (Lepidoptera) was quantified in an alvar landscape in the Ottawa valley through a comparison of burned and unburned alvar woodland. The two adjacent habitats on the same successional gradient were sampled by sweeping with additional data from pitfall traps for bees and by direct observation with close focus binoculars and occasional verification through capture with a net for butterflies. The sampling was done during 11 visits in 2008 beginning 16 May and ending 13 September. Both bee and butterfly diversity were higher in the post-fire burned alvar woodland compared to the adjacent unburned woodland based on species richness, number of individuals and Brillouin’s Biodiversity Index which takes evenness and heterogeneity into account. No bees were captured in the unburned area, but 34 species and 201 individuals were captured in the burned site. The most abundant bee species was Augochlora aurata . Lepidoptera were represented in the burned site by 35 species and 408 individuals compared to 15 species and 21 individuals in the unburned woodland. The most common butterfly species in the burned woodland was Callophrys polios. The higher diversity of pollinators in the burned site was correlated with both higher vascular plant diversity and much higher cover and frequency values for insect-pollinated plants providing nectar and pollen including flowering shrubs such as Amelanchier alnifolia var. compacta, Arctostaphylos uva-ursi and Prunus virginiana . The burned site also provided more cover of larval food plants for butterflies and apparently more nesting sites for bees. We suggest that a decrease in fire frequency and in the availability of open successional habitats are contributing factors in the decline of pollinators, and that endangered ecosystems where fire has been a natural phenomenon may require fire or fire- simulated management to sustain their biodiversity. Key Words: pollinators, biodiversity, Lepidoptera, Hymenoptera, alvar, succession, fire, Ontario, Canada.

Pollination plays a crucial role economically and and industrial development (Kevan 1999) and climate ecologically (Kevan and Phillips 2001; Luck et al . change (Parmesan et al. 1999). However, a decline in 2003; Klein et al. 2007; Kremen et al . 2007). Bees pollinators could also be caused by loss of early suc - (Hymenoptera) are the most important group of polli - cessional stage plant communities resulting from the nating insects in the world (Biesmeijer et al. 2006) and cessation of natural ecological processes such as fire. it is estimated that there are over 800 species in Cana - The southern Ontario landscape in pre-settlement da (Sheffield, personal communication). Butterflies times included a variety of successional habitats, (Lepidoptera) are another important pollinator group largely as a result of natural fires caused by lightning. in North America with over 297 species of butterflies Incidence of fire was also high as a result of aboriginal in Canada (Layberry et al. 1998). Recent biodiversity communities using fire for agricultural purposes and surveys have reported declines in both groups world - to improve hunting (Day 1953; Bakowsky and Riley wide (Committee on the Status of Pollinators 2006; 1994). The arrival of European settlers in North Amer - White and Kerr 2006), particularly, in populated regions ica led to a vastly reduced frequency of fire as a result including parts of Canada such as Southern Ontario. of fragmentation of wooded landscape, roads acting as The decline of pollinators has been attributed to a num - fire breaks, and direct fire suppression to protect com - ber of possible causes including the use of pesticides mercial wood and homes. Newly begun successions (Kevan et al. 1997), the loss of habitat due to anthro - became rare and older successions proceeded from the pogenic activities in the form agricultural intensification open earlier stages to later seral stages with increasing

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tree cover. Now in a fragmented landscape without fire for a few hundred years, many natural areas and entire landscapes have lost or are about to lose the open and semi-open habitats. The fact that certain species need early successional stages is well known. Controlled fire is currently used to maintain ecosystem diversity (Lee et al. 1998) with management processes some - times adjusted to resemble pre-settlement conditions based on historical records (Whelan 1995) and execut - ed in such a way as to reduce any negative impact on arthropod populations (Siemann et al. 1996). Fire man - agement is well developed in some regions, but it is not utilized at all in others and the importance of successional habitats produced by fire to insects is not well documented, especially for pollinating insects (Bradstock et al. 2005; Nol et al . 2006; Parr and Anderson 2006; Dixon 2009). Although some authors have concluded that catastrophic events such as fire promote pollinator diversity through the establish - ment of a diverse patchwork of habitats at different succesional stages (Swengel 1996; Potts et al., 2001, 2003), just how important this promotion is and how widespread it is remains unclear. Here we use an alvar landscape in the Ottawa valley that was partly burned nine years previously to provide evidence for the importance of successional habitat to pollinating insects, specifically bees (Hymenoptera) and butterflies (Lepidoptera). Alvars, i.e., naturally open areas of thin soil over essentially flat limestone or marble rock with trees absent or not forming a con - tinuous canopy, are among the most unique and threat - ened habitats in Canada (Catling and Brownell 1999; Brownell and Riley 2000) and are generally consid - ered to be globally imperiled (Reschke et al. 1999). Earlier studies (Catling et al. 2001, 2002; Catling and Sinclair 2002; Catling 2009; and Catling et al. 2010) have suggested the importance of post fire succession to diversity of plants and ground dwelling insects in these imperiled ecosystems, but pollinators had not been studied. Specifically we compare two sites on the same successional gradient: a semi-open boreal wood - FIGURE 1. Two views of the unburned alvar woodland study land that represents climax vegetation for the site, and area on the Burnt Land Alvar west of Ottawa. Above, a nearly adjacent site that previously had similar vege - fallen and drought-killed trees of Abies balsamea tation but had burned nine years before and developed and Picea glauca with living plants of the former as well as Pinus strobus, Thuja occidentalis , and Popu - into a relatively long lasting successional alvar shrub - . Below a more shaded area with the land (Catling 2009). lus tremuloides ground flora dominated by Carex eburnea and mosses. Photo by P. M. Catling at 45.2569 N, –76.1437 W, in Methods late May 2008. The study area The study area is part of an alvar landscape within Burnt Lands Provincial Park 6 km NE of Almonte in 45.2507°N, -76.1437°W. Based on personal observa - the Ottawa valley of Ontario. Alvars are unusual eco - tion and examination of aerial photographs, both of systems with a fragmented distribution in North these study areas had been semi-open, mixed boreal America and are considered globally imperiled. The forest until 23 June 1999 when a fire swept through woodland study site included 4 hectares (approximate - 152 acres including the southern study site. The forest ly 10 acres) centered at 45.2569°N, -76.1437°W. The that remained and the forest that burned (Figure 1) corresponding burned woodland study site 0.5 km to were dominated by Abies balsamea , Picea glauca, the southeast also included 4 hectares centered at Pinus strobus, Thuja occidentalis , and Populus tremu - 2011 TAYLOR AND CATLING : B URNED AND UNBURNED ALVAR WOODLAND 299

FIGURE 2. Left, alvar shrubland developed from alvar woodland burned 9 years previously. Flowering shrubs of Amelanchier alnifolia var. compacta , very important to pollinating insects, can be seen below a dead Thuja occidentalis . Right, flowering inflorescence of Amelanchier alnifolia var. compacta, a species that becomes very abundant following fire in alvar woodland and serves as a major source of pollen and nectar for pollinating insects. Photo taken by P. M. Catling at 45.2507°N, -76.1437°W in late May 2008. loides with an understory of mosses including Hylo - tions were made along transects 100 m in length in comium splendens and Dicranum polysetum and occa - each site and during sunny, mild or warm conditions. sional depauperate shrubs including Juniperus com - Information on bees was also derived from pitfall traps munis . Nine years after the fire the burned area had as bycatch of a study of ground-dwelling insects. Pan developed into a long-lasting successional shrubland traps were not used because we did not want to stress (Figure 2) dominated by shrubs such as Prunus virgini - the pollinator populations at the site and we consid - ana, Arctostaphylos uva-ursi, Amelanchier alnifolia ered that the limited sweeping and accessory infor - var. compacta and Symphoricarpos albus , and herbs mation from the pitfall traps would provide sufficient such as Danthonia spicata and Carex richardsonii. information to reveal a trend. Ten pitfall traps (15 cm Fire is a natural process on alvars and evidence of × 10 cm × 5 cm deep) were set out at each site. The past fire is commonly found (Catling and Brownell traps were buried so that the tops were flush with the 1999; Jones and Reschke 2005). The Burnt Lands have ground surface and each trap was filled with antifreeze long been known to be particularly subject to fire on with a drop of soap to half depth. The traps were account of shallow soil on an elevated plateau of porous checked five days after setting. The survey continued limestone rock. The area was named the Burnt Lands from spring through summer to fall with several gaps. by settlers in 1870, at the time of the second most recent The dates for recording Lepidoptera, collecting bees fire. Additional information on the two study sites is and checking the traps were 16 May, 1, 9 June, 1, 5, 12 available in Catling (2009). July, 16, 21, 26 August, and 8, 13 September. Collection, identification, biodiversity measures and Extensive observations on 10 days during two years floristic data prior to the study revealed many hundreds of pollina - Lepidoptera in the groups Hesperoidea and Papil - tors in the burned area on each occasion compared to ionoidea were recorded for a 30 minute period during less than a dozen in equal areas of forest during equal each visit and bees were collected for a second 15 amount of time. This suggested that differences be - minute period by sweeping vegetation including flow - tween pollinators in the burned area and the surround - ering herbs and shrubs. The observations and collec - ing woodland were very substantial with the woodland 300 THE CANADIAN FIELD -N ATURALIST Vol. 125 i i i s s s r r r a a a a a a a a u u u i i i i i i i i l l l l l l l l - - - a a s l l o o o o o o o o a a a i m m m f f f f f f f f l a a a a a a a a a v v v u u i i i i i i i i u u u a n n n n n n n n n c c u u u n n n n n n n n b b b

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having very low diversity and numbers. Had this been any less obvious, the sampling procedure here may have involved replicates and detailed statistical analy - ses. However, considering the extent to which the trend was clear, we decided that it was only necessary to quantify it and to ensure that the transects were rep - resentative. Based on a general survey of the area, these transects were fully representative of the burned area and the surrounding forest in both vegetation and top ography which varied over distances much larger than 100 m. The Lepidoptera – Hesperioidea and Papilionoidea were identified by P. M. Catling using Layberry et al. (1998). Hymenoptera – Apoidea were identified by A. Taylor and J. Gibbs using Packer et al. (2007), Romankova (2003), Mitchell (1960) and Gibbs (sub - mitted). Bees collected were deposited in the bee col - lection of L. Packer at York University. Biodiversity of collected insects was compared with respect to total number of species and numbers of individuals within species and with regard to Bril - louin’s Index which is appropriate for collections (Krebs 1999). The calculation was made using soft - ware provided by Krebs (2008). To compare the pollinator diversity results with the potential value of the vegetation at each of the sites to pollinating insects, we compared average cover and total frequency values for insect pollinated plant species known to, or suspected of, providing pollen or nectar rewards. This included excluding all wind- pollinated species from data that were obtained as part of a floristic inventory based on thirty 1 m 2 quadrats placed 3 m apart along a transect at each site (Catling 2009). The cover was then estimated for each plant species within each quadrat as ½ of the surface area of all plants to 2 m tall (i.e., the percentage of the square meter that would be covered by all vegetation overlapping the square if all plants were laid flat and not overlapping.). The average cover for each species was then summed and expressed as a percentage of the total average cover of all species at each site. Frequen - cy was determined as the number of quadrats within which a species occurred at a site. Both of these meas - ures suggest the relative biomass and abundance of plants beneficial to pollinators. Although biodiversity and abundance are not direct indicators, like the num - ber of flowers, they are considered to be reasonable surrogates since there is a clear relationship between flower number and both biomass and abundance. FIGURE 3. Histograms showing number of species, number of individuals, and the value of Brillouin’s Index for Results burned and unburned alvar woodland. The difference in diversity of bees between wood - land and successional shrubland (that was woodland only 9 years earlier) was substantial. In the woodland one individual Bombus sp. and one individual Osmia 173 were swept from flowering plants and 46 were sp. were observed in flight and no bees were captured obtained in pitfall traps (Table 1). Hundreds of bees with nets or in traps. In the burned area, 34 species were seen but not captured during the standard col - and 219 individuals were captured, and of the latter, lecting procedure in the burned area. The most abun - 302 THE CANADIAN FIELD -N ATURALIST Vol. 125 . d n a l d o o w

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dant bee species caught was Augochlora aurata able nesting sites for bees including Andrena nasonii, (Smith) with 45 individuals (Table 1) with Andrena Lasioglossum foxii, and Lasioglossum imitatum which nasonii (Robertson) , Ceratina calcarata (Robertson), were among the most common bee species caught and Lasioglossum (Evylaeus ) foxii (Robertson) among within the burnt alvar habitat (Table 2). Each of the the most common species captured (Table 1). More bee species noted above nest in the ground (Grixti species and individuals of Lepidoptera in the groups and Packer, 2006). The abundance of ground-nesting Hesperoidea and Papilionoidea were also evident in bees in the burned site is not surprising as fire tends the burned site which had 35 species and 408 indi - to remove leaf litter and debris that might otherwise viduals compared to 15 species and 21 individuals in cover potential nest sites. As succession proceeds in the unburned woodland (Table 2). The most abundant post-fire habitat more cavities become available for butterfly in the burned area was the locally rare Cal - nests as a result of dead trees and also from the estab - lophrys polios (Layberry et al. 1982). lishment of pithy stemmed mid-successional stage The value for Brillouin’s biodiversity index was species such as Rubus spp. This may explain the abun - higher for the Lepidoptera in the burned area but could dance of cavity nesting species such as Augochlora not be calculated for bees in woodland since none were aurata and Ceratina calcarata (Table 2). captured. The value of the index was higher for bees Our study suggests that successional shrubland that found in the burned site than for Lepidoptera in either develops after fire in semi-open, conifer-dominated site (Figure 3). alvar woodland is far more important for pollinating The cover of insect-pollinated plants in the burned insects than the original woodland. It supports and area was five times greater than that of the woodland quantifies earlier general observations and detailed and represented 64.24% of the total as compared to studies in other regions (Fahrig 2003; Grixti and Packer 16.62% for the woods. Flowering plants with substan - 2006, Swengel and Swengel 2007, Vogel et al. 2007) tial nectar and pollen resources such as Amelanchier that indicate the importance of successional habitat in alnifolia var. compacta , Arctostaphylos uva-ursi and providing nesting sites and floral resources (Fahrig, Prunus virginiana had much higher cover values and 2003; Grixti and Packer, 2006). Early successional were much more frequent in the successional shrub - stages continued for some time (decades to a few hun - land (Table 3). Among the most important individual dred years) after the cessation of ecological processes species, Amelanchier alnifolia var. compacta had ap - such as fire which occurred regularly up to 100-200 proximately 15 times the cover value in the succession - years ago. The lag period now appears to be coming to al habitat, Arctostaphylos uva-ursi had about 5 times an end and the effects of lack of fire are increasingly the cover and Prunus virginiana had more than 22 obvious. We suggest that the loss of fire and open suc - times the cover than in unburned woodland. Even when cessional habitats is a contributing factor in the decline present as relict individuals in the woodland, these of pollinators, and that endangered ecosystems, such as species bloomed sparingly there. alvars, where fire was a natural phenomenon require fire or fire-simulated management to sustain their bio - Discussion diversity. The basis for the increased pollinator diversity in the successional shrubland is evidently the vastly increased Acknowledgements value of this habitat to pollinators. The diversity of pol - Helpful comments were provided by Laurence Pack - linators is at least partially dependent on habitat qual - er and Ross Layberry. Brenda Kostiuk assisted with ity (Winfree et al., 2007). If a habitat does not offer field work. We also thank J. Gibbs for identification of pollinators accommodation for larval stages and/or flo - Dialictus spp. and Cory Sheffield for verification of ral resources for foraging adults, it would be unsuitable Megachilidae spp. to sustain pollinator communities. With regard to floral resources, the burned woodland is far superior to the Literature Cited unburned woodland being dominated by flowering Bakowsky W., and J. L. Riley. 1994. A survey of the prairies shrubs providing both abundant pollen and nectar for and savannas of southern Ontario. Pages 7-16 in Proceed - bees and food sources for both adult and larval but - ings of the thirteenth North American prairie conference. terflies. Although Arctostaphylos uva-ursi , the larval Edited by R. G. Wickett, P. D. Lewis, A. Woodliffe and P. food plant of Callophrys polios was only 1.46 times Pratt. Department of Parks and Recreation, Windsor, as frequent in the burned area, its cover value was Ontario, Canada. four times greater (Table 3) providing an explanation Biesmeijer, J. C., S. P. M. Roberts, M. Reemer, R. for the much greater abundance of the butterfly there. Ohlemüller, M. Edwards, T. Peeters, A. P. Schaffers, S. G. Potts, R. Kleukers, C. D. Thomas, J. Settele, and Despite the higher density of vegetation in the burned W. E. Kunin. 2006. Parallel declines in pollinators and area there was extensive open ground including rock, insect-pollinated plants in Britain and the Netherlands. shallow bare soil and turf. Many of the shrubs emerged Science 313 (5785): 351-354. from cracks in the shallowly underlying limestone rock. Bradstock, R., A. M. Bedward, A. M. Gill and J. S. Cohn. The more extensive open ground likely increased avail - 2005. Which mosaic? A landscape ecological approach for 2011 TAYLOR AND CATLING : B URNED AND UNBURNED ALVAR WOODLAND 305

evaluating interactions between fire regimes, habitat and Klein, A. M., B. E. Vaissiere, J. H. Cane, I. Steffan-Dewen - animals. Wildlife Research 32 (5): 409-423. ter, S. A. Cunningham, C. Kremen, and T. Tscharntke. Brownell, V. R., and J. L. Riley. 2000. The alvars of Ontario, 2007. Importance of pollinators in changing landscapes significant alvar natural areas in the Ontario Great Lakes for world crops. Proceedings of the Royal Society 274 region. Federation of Ontario Naturalists, Don Mills, On- (1608): 303-313. tario. 269 pages. Krebs, C. 1999. Ecological methodology, 2 nd edition. Addi - Catling, P. M. 2009. Vascular plant biodiversity in burned and son, Wesley Longman Inc., New York. 620 pages. unburned alvar woodland: more evidence of the impor tance Krebs, C. 2008. Ecological Methodology, programs for of disturbance to biodiversity and conservation. Canadi - ecological methodology, 2 nd edition. Exeter Software, an Field-Naturalist. 123(3): 240-245. Setauket, New York Catling, P. M., and V. R. Brownell. 1999. The alvars of the Kremen, C., N. M. Williams, A. M. Aizen, B. Gemmill- Great Lakes region. Pages 375-391 in Savanna, barren Herren, G. Lebuhn, R. Minckley, L. Packer, S. G. and rock outcrop communities of North America. Edited Potts, T. Roultson, I. Steffan-Dewenter, D. P. Vazquez, by R. C. Anderson, J. S. Fralish, J. M. Baskin. Cambridge L. Adams L. E. E. Crom, S. S. Greenleaf , T. H. Keitt, University Press, Cambridge, UK. A. M. Klein, J. Regetz, and T. H. Ricketts . 2007. Polli - Catling P. M., H. Goulet, R. Bennett, and B. Kostiuk . nation and other ecosystem services produced by mobile 2010. Orthopterans (Orthoptera), ground beetles (Coleop - organisms: a conceptual framework for the effects of land- tera: Carabidae), and spiders (Araneae) in burned and use changes. Ecological Letters 10(4): 299-314. unburned alvar woodlands – some evidence of the impor - Layberry, R. A., P. W. Hall, and J. D. Lafontaine . 1998. The tance of postfire succession to insect diversity. Journal of butterflies of Canada. NRC Press, Ottawa. 280 pages. the Entomological Society of Ontario. 141: 27-37. Layberry, R. A., J. D. Lafontaine, and P. W. Hall. 1982. Catling P. M., and A. Sinclair . 2002. Initial beneficial effects Butterflies of the Ottawa District. Trail and Landscape 16: of fire and bulldozing on Neglected Milkvetch, Astragalus 3-59. neglectus , in an eastern Ontario Alvar Woodland. Canadian Luck, G. W., G. C. Daily, and P. R. Ehrlich . 2003. Popula - Field-Naturalist 116: 640-642. tion diversity and ecosystem services. Trends 18(7): 331- Catling P. M, A. Sinclair, and D. Cuddy . 2001. Vascular 336. plants of a successional alvar burn 100 days after a severe Mitchell, T. B. 1960. Bees of the eastern United States. Vol - fire and their mechanisms of re-establishment. Canadian ume I. The North Carolina Agricultural Experiment Sta - Field-Naturalist 115: 214-222. tion. Catling P. M., A. Sinclair, and D. Cuddy. 2002. Plant com - Nol, E., H. Douglas, and W. J. Crins. 2006. Responses of munity composition and relationships of disturbed and syrphids, elaterids, and bees to single-tree selection har - undisturbed alvar woodland. Canadian Field-Naturalist vesting in Algonquin Provincial Park, Ontario. Canadian 116: 571-579. Field-Naturalist 120: 15-21. Committee on the Status of Pollinators . 2006. Status of Packer, L., J. Genaro, and S. C. Sheffield . 2007. The Bee Pollinators in North America. The National Academies Genera of Eastern Canada. Canadian Journal of Arthro - Press, Washington, D.C. pod Identification Number 3. available online at: http:// Day, G. M. 1953. The Indian as an ecological factor in the www.biology.ualberta.ca/bsc/ejournal/pgs_03/pgs_03.html. northeastern forest. Ecology 34: 329-346. Parmesan, C., N. Ryrholm, C. Stefanescu, J. K. Hill, C. Dixon, K. W. 2009. Pollination and Restoration. Science D. Thomas, H. Descimon, B. Huntley, L. Kaila, J. 325: 571-572. Kullberg, T. Tammaru, W. J. Tennent, J. A. Thomas , Fahrig, L. 2003. Effects of habitat fragmentation on biodi - and M. Warrant. 1999. Poleward shifts in geographical versity. Annual Review of Ecology, Evolution and Sys - ranges in butterfly species associated with regional warm - tematics 34: 487-515. ing. Nature 399: 579-583. Gibbs, J. (submitted) Revision of the metallic species of Dial - Parr, C. L., and A. N. Anderson . 2006. Patch mosaic burn - ictus in Canada (Hymenoptera, Halictidae, Lasioglossum). ing for biodiversity conservation: a critique of the pyro - Zootaxa. 776 pages. diversity paradigm. Conservation Biology 20: 1610-1619. Grixti, J., and L. Packer. 2006. Changes in the bee fauna of doi: 10.1111/j.1523-1739.2006.00492.x an old field site in southern Ontario, revisited after 34 years Potts, S. G., A. Dafni, and G. Ne’eman . 2001. Pollination (Hymenoptera: Apoidea). Canadian Entomologist 138: of a core flowering shrub species in Mediterranean phyr - 147-164. gana: variation in pollinator diversity, abundance, and Jones, J., and C. Reschke . 2005. The role of fire in Great effectiveness in response to fire. Oikos 92: 71-80. Lakes alvar landscapes. Michigan Botanist 44(1): 13-27. Potts, S. G., B. Vulliamy, A. Dafni , G. Ne’eman , C. Kevan, P. G. 1999. Pollinators as bioindicators of the state O’Toole, S. Roberts, and P. Wilmer . 2003. Response of of the environment: species, activity and diversity. Agri - plant-pollinator communities to fire: changes in diversity, cultural Economics and Environment 74: 373-393. abundance and floral reward structure. Oikos 101: 103- Kevan, P. G., C. F. Greco, and S. Belaoussoff . 1997. Log- 112. normality of biodiversity and abundance in diagnosis and Reschke, C., R. Reid, J. Jones, T. Feeney, and H. Potter . measuring of ecosystem health: pesticide stress on polli - 1999. Conserving Great Lakes alvars. The Nature Conser - nators on blueberry heaths. Journal of Applied Ecology vancy, Chicago. http://www.epa.gov/glnpo/ecopage/shore/ 34: 1122-1136. alvars /#Technical%20Report . Kevan, P. G., and T. P. Phillips. 2001. The economic impacts Romankova, T. 2003. Bees of genus Colletes of Ontario of pollinator declines: an approach to assessing the con - (Hymenoptera, Apoidea, Colletidae). Journal of the Ento - sequences. Conservation Ecology 5(1): 8. [online] URL: mological Society of Ontario 134: 91-106. http://www.consecol.org/vol5/iss1/art8/ 306 THE CANADIAN FIELD -N ATURALIST Vol. 125

Siemann, E., J. Haarstad, and D. Tilman . 1996. Short term Vogel, J. A., D. M. Debinski, R. R. Koford, and J. R. Miller. and long term effects of burning on Oak savanna arthro - 2007. Butterfly responses to prairie restoration through pods. American Midland Naturalist 137: 349-361. fire and grazing. Biological Conservation 140 (1-2): 78-90. Swengel, A. B. 1996. Effects of fire and hay management on Whelan, R. J. 1995. The ecology of fire. Cambridge Uni - abundance of prairie butterflies. Biological Conservation versity Press, New York 76: 73-85. White P., and J. T. Kerr. 2006. Contrasting spatial and tem - Swengel, A. B., and S. R. Swengel . 2007. Benefit of perma - poral global change impacts on butterfly species richness nent non-fire refugia for Lepidoptera conservation in fire- during the 20 th century. Ecography 29: 908-991. managed sites. Journal of Insect Conservation 11(3):156- Winfree, R., T. Griswold, and C. Kremen. 2006. Effect of 168. human disturbance on bee communities in a forested eco - system. Conservation Biology 21(1): 213-223.

Received 17 March 2010 Accepted 8 June 2010