Pedobiologia 47, 288–299, 2003 © Urban & Fischer Verlag http://www.urbanfischer.de/journals/pedo Habitat use patterns by ground beetles (Coleoptera: Carabidae) of northeastern Iowa Kirk J. Larsen1*, Timothy T. Work2 and Foster F. Purrington3 1 Department of Biology, Luther College, 700 College Drive, Decorah, Iowa 52101, USA 2 Department of Renewable Resources, 442 Earth Sciences Building, University of Alberta, Edmonton, Alberta, T6G-2H1, Canada 3 Department of Entomology, 103 Botany & Zoology Building, The Ohio State University, 1735 Neil Avenue, Columbus, Ohio 43210, USA Submitted April 9, 2001 · Accepted December 27, 2002 Summary Ground beetle assemblages were monitored in six different habitats (tallgrass prairie, oats, corn, soybean, old-field, woods) at four sites in northeastern Iowa from 1994 to 1998. The objective of this study was to quantify the influence of habitat type on the activity and distribution of ground beetles. Over five years, 13,654 ground beetles representing 107 different species were captured. Of these, 14 species represented 85 % of the captured beetles. Based on habitat use, we catego- rized 24 as generalist species, 14 as agricultural species, 12 as grassland species, 39 as prairie specialists, and 19 as wood- land species. Tallgrass prairie hosted a significantly more (P < 0.05) diverse assemblage of ground beetles than was found in the other habitats. Prairie also had a higher percentage of habitat specialists in its assemblage than did the less stable agricultural habitats which were dominated by generalists. NMS ordination and indicator species analysis revealed distinct ground beetle assemblages and identified indicator species in the various habitats, allowing species assemblages to be used as habitat indicators. Key words: Coleoptera, Carabidae, ground beetles, pitfall traps, tallgrass prairie Introduction Ground beetles or carabids (Coleoptera: Carabidae) 1964). Although a large and ubiquitous group, many are one of the most common and abundant beetle fam- species of ground beetles are highly selective and re- ilies, comprised of about 40,000 known species (Lövei stricted to a particular habitat (Thiele 1977; Evans and Sunderland 1996). Of the epigaeic insects, ground 1983; Niemelä et al. 1992). This habitat selectivity beetles are among the most numerous and most impor- makes carabids well suited to be used as ecological in- tant groups (Harris & Whitcomb 1974), primarily as dicators of changes within terrestrial communities polyphagous predators of other invertebrates (Whit- (Thiele 1977; Freitag 1979; Dufrêne et al. 1990; comb & Bell 1964; Larochelle 1990; Loreau 1990). As Maelfait & Desender 1990; Larsen et al. 1996), as they predators, carabids tend to patrol the soil surface and have been used as ecological indicators to assess grass- attack other epigaeic invertebrates (Whitcomb & Bell land use in England (Eyre & Rushton 1989). *E-mail corresponding author: [email protected] 0031-4056/03/47/03–288 $15.00/0 Habitat utilization by NE Iowa carabids 289 Except for the agriculturally important species, 97.2-ha native remnant tallgrass prairie managed by ground beetles in Iowa have been relatively unstudied. the Iowa Department of Natural Resources, is located This has been especially true of the ground beetles of in Howard County (UTM zone 15, 550105E, the geologically distinct northeastern corner of Iowa. 4809715N). Hayden Prairie is surrounded completely In this study, we examined the influence of habitat on by fields of corn (Zea mays L.), and soybean (Glycine the activity and distribution of northeastern Iowa max (L.) Merr.). Anderson Prairie is a 9.4-ha recon- ground beetles. Over a five-year period from 1994 to structed tallgrass prairie located on the Luther College 1998, pitfall traps were used to monitor ground beetle campus in Decorah, Winneshiek County (UTM Zone assemblages in a variety of habitats at four sites in 15, 597396E, 4796283N). Anderson Prairie is man- northeastern Iowa. One common characteristic among aged by Luther College, and is surrounded by a bur oak these sites was the presence of tallgrass prairie habitat. (Quercus macrocarpa Michx.) and shagbark hickory The primary objective of this research was to inven- (Carya ovata (Mill.) Koch) forest known as Hickory tory the ground beetles found in a variety of habitats in Ridge Woods to the northeast and northwest, and was NE Iowa to identify potential habitat specialists for use bounded on the southwest by continuous cropping of as possible ecological indicators. We then intend to use oats (Avena sativa L.). To the southeast is old-field these indicator species to monitor the effects of man- habitat. Effigy Mounds National Monument, managed agement practices such as fire in tallgrass prairies on by the National Park Service, is located on bluffs over- prairie-obligate invertebrates. looking the Mississippi River on the border of Allama- kee and Clayton Counties (UTM Zone 15, 647536E, 4774137N). Effigy Mounds National Monument has Materials and Methods 25-ha of primarily reconstructed prairie divided be- tween a northern unit and southern unit, along with nu- Study Sites merous hill prairie remnants of less than 0.25-ha each. These prairies are completely surrounded by oak/hick- From 1994 through 1998, ground beetles were inten- ory forests, although nearby are several soybean, corn, sively sampled from a variety of habitats at four and old-field habitats. Chipera Prairie is a 31.2-ha na- sites in northeastern Iowa (Fig. 1). Hayden Prairie, a tive remnant tallgrass prairie managed by the Win- Fig. 1. Locations of four sites in Northeastern Iowa sampled from 1994 to 1998 for ground beetles from six different habitats (prairie, old- field, oats, corn, soybean, woods) with pitfall traps Pedobiologia (2003) 47, 288–299 290 Kirk J. Larsen et al. neshiek County Conservation Board. Located in Win- specified a priori (Clarke 1993). For this analysis, neshiek County (UTM Zone 15, 580825E, 4775593N), Sorenson’s distance (also referred to as Bray-Curtis this site includes a 2-ha wooded area and is completely distance) was used and significance of ordination axis surrounded by corn and soybeans, with oats and old- was evaluated by comparing the solution stress of the field habitats also present. observed data to the stress observed in 50 randomiza- tions of the observed data. Because the potential con- servation value of tallgrass prairie habitat for rare Ground Beetle Sampling species was of specific interest within this study, all Ground beetles were collected in pitfall traps exposed species were included in this analysis. in the field for one-week-long periods in early-June, Habitat preference of individual beetle species was mid-July, and late August from 1994 through 1998. evaluated using indicator species analysis (Dufrêne Each trap was constructed from one 473 mL plastic and Legendre 1997). Indicator species analysis is a cup (9 cm dia) placed into the ground so the lip of the randomization-based test that compares the relative cup was at or slightly below the ground surface. Each abundance and the relative frequency of individual cup was fitted with a funnel constructed from a 207 species across different sampling areas and expresses a mL casual cup insert (Sweetheart® Cup Company, species’ affinity for a sampling area as % indication of Chicago, Illinois) to prevent beetle escape. Approxi- a particular sampling area (Dufrêne and Legendre mately 50 mL of 50 % propylene glycol was then 1997). added as a preservative. Statistical comparisons of all samples combined During each trapping period, 12 traps were placed in among tallgrass prairie (n = 4), woodland (n = 2), and a single transect line at 10 m intervals in tallgrass active agricultural habitats (n = 6) were performed for prairie (n = 4), woods (n = 2), old-field (n = 1), and ac- the total number of ground beetles, species richness, tive agricultural habitats (corn, oats, or soybeans, and activity density (average number of ground beetles n = 6) present at each site. After each trapping period, caught per trap per day) using the nonparametric analysis of variance Kruskal-Wallis test (Zar 1999). traps were removed and holes refilled. Damaged or Ecological indices were calculated both on raw count disturbed traps were noted and excluded from the data and data transformed to number of beetles cap- analysis. Samples were washed and stored in 70 % tured per trap per day. To test for significant differ- ethanol. Ground beetles were then identified to species ences among the Shannon diversity values, we used a using keys in Lindroth (1961–1969) and Noonan pairwise comparison test by Hutcheson (1970) de- (1991), and names standardized using Bousquet and scribed by Zar (1999). Since the trends and results Larochelle (1993). Voucher specimens are housed in were the same, only raw count data analyses are re- the reference insect collection in the Hoslett Museum ported. of Natural History, Luther College, Decorah, Iowa. Accumulation curves were generated using Esti- mateS software (Colwell 1997). Curves generated Ground Beetle Faunal Analysis compare cumulative species number and sampling ef- fort for all annual samples from each site and habitat The total abundance of ground beetles and species type. richness was determined for each habitat. Because of Five classifications regarding habitat specialization variation in the number of recovered traps and length were used to categorize each ground beetle species as of trap exposure in the field, abundance data were follows: generalist species are those well represented transformed to number of beetles captured per trap per in all habitat types; grassland species are those found day for some of the analyses. We calculated Shannon’s primarily in prairie and old-field habitats, with some diversity index (H’) using log base e, Pielou’s even- occasionally occurring in agricultural but not wooded ness index (J’) (Krebs 1989), and French’s (1994) hi- habitats; agricultural species are those with over 70 % erarchical richness index (HRI) for the ground beetle of collected individuals in cropped agricultural habi- fauna of each habitat type.