Kirk J. Larsen

Habitat use patterns by ground beetles (Coleoptera: Carabidae) of northeastern Iowa

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 categorized 24 as generalist species, 14 as agricultural species, 12 as grassland species, 39 as prairie specialists, and 19 as woodland species. Tallgrass prairie hosted a significantly more (P

Differences in ground beetles (Coleoptera: Carabidae) of original and reconstructed tallgrass prairies in northeastern Iowa, USA, and impact of 3-year spring burn cycles

Ground beetle assemblages were monitored at four tallgrass prairie sites burned on 3-year cycles in northeastern Iowa. The objectives of this study were to quantify differences in carabid communities between original and reconstructed tallgrass prairies, and to determine the responses of ground beetles to 3-year cycles of early spring fire commonly used to manage tallgrass prairies. Using pitfall traps, ground beetle assemblages in two original and two reconstructed tallgrass prairies were compared between 1994 and 1998, where beetles were sampled annually (0-, 1-, and 2-year post-fire conditions) from plots burned every 3 years. When burned, the greatest abundance, activity density, and species richness of carabid beetles occurred the year immediately following a spring burn, with abundance declining steadily with increased time since burning. Overall ground beetle diversity as determined by Shannons diversity index was greatest in original tallgrass prairies several years after a fire. Some species of ground beetles were found only in original prairies, while others were found primarily in reconstructed prairie. Similarly, some species were more abundant the year immediately following a burn, while others were found in greater abundance with increased time since fire. NMS ordination and indicator species analysis clearly show differences in carabid species between original and reconstructed tallgrass prairies, but did not show differences among burn treatments.

Tending Ants (Hymenoptera: Formicidae) Regulate Dalbulus quinquenotatus (Homoptera: Cicadellidae) Population Dynamics

Abstract Population dynamics of colonies of the mymecophilous leafhopper Dalbulus quinquenotatus DeLong & Nault were recorded in the laboratory in the presence and absence of the tending ant, Formica fusca (L.). These experiments used colonies of leafhoppers started with five male and five female adults on a single Tripsacum dactyloides L. plant. The first experiment consisted of eight leafhopper colonies, four with tending ants and four without. The second experiment used 16 leafhopper colonies, eight with tending ants and eight without, with four of each of these ant treatments also with Nabis americoferus Carayon predators. The numbers of young nymphs, older nymphs, and adult leafhoppers, along with host plant condition were recorded every 2–3 d for 62 d for both experiments. Nontended leafhopper colonies exploded and overwhelmed their host plants, killing them in an average of 39.0 d, resulting in the extirpation of those leafhopper colonies. Ants maintained leafhopper colonies by regulating population dynamics, with colonies of leafhoppers tended by ants being significantly smaller (P < 0.02) and developing from egg to adult significantly slower (P < 0.001) than colonies of nontended leafhoppers. Ant-tended leafhopper colonies did not overwhelm their host plants during either experiment, as the ants removed excess honeydew and leafhopper exuvia, thus maintaining a constant supply of honeydew. Ants were observed protecting leafhoppers from nabid predators, although this protection did not significantly influence leafhopper population size or length of egg to adult development.

Temporal Resource Switching by Ants between Honeydew Produced by the Fivespotted Gama Grass Leafhopper (Dalbulus quinquenotatus) and Nectar Produced by Plants with Extrafloral Nectaries

Abstract A field study was conducted in Jalisco, Mexico, to quantify temporal resource switching by ants between honeydew produced by the fivespotted gama grass leafhopper, Dalbulus quinquenotatus, and nectar produced by plants with extrafloral nectaries (EFNs). Four plant taxa (Acacia pennatula, Leucaena esculenta, Lobelia laxiflora and Lysilona sp.) which produced nectar from EFNs were monitored for ants during the dry and wet seasons in ecological communities where D. quinquenotatus was tended by ants on their gama grass (Tripsacum spp.) hosts. These plants with EFNs were visited preferentially in May (the driest month) by Brachymyrmex obscurior, a common ant species that tended D. quinquenotatus in all months except May. Our results suggest temporal resource switching by ants between plants with EFNs and D. quinquenotatus. This cycle is regulated by the amount of nectar produced by plants with EFNs and honeydew produced by D. quinquenotatus. Although B. obscurior was the most common ant to visit plants with EFNs and tend D. quinquenotatus, four additional species of ants were also associated with both food resources.

Evaluation of land use and water quality in an agricultural watershed in the USA indicates multiple sources of bacterial impairment

Pathogens are the number one cause of impairments of assessed rivers and streams in the USA and pose a significant human health hazard. The Dry Run Creek Watershed in Northeast Iowa has been designated as impaired by the State of Iowa because of high levels of Escherichia coli bacteria. To investigate the nature of this impairment, land use and stream bank assessments were coupled with comprehensive water quality monitoring. Physical, chemical, and biological parameters were measured at 13 different sites in the watershed, including pH, temperature, conductivity, dissolved oxygen, turbidity, total Kjeldahl nitrogen, ammonia-N, nitrate + nitrite-N, total phosphorus, and E. coli. In addition, benthic macroinvertebrate communities were analyzed at seven sites, and optical brightener tests were performed late in the season. Results identified segments of the watershed that were more prominent contributors of E. coli, and correlations were observed between levels of E. coli and several chemical parameters, including ammonia-N, total Kjeldahl nitrogen, and total phosphorus. Interestingly, distinct sites emerged as more prominent contributors of these elements during rain vs. non-rain events, suggesting different types of sources. Both the amount of rainfall and the time elapsed between the rain event and the sampling influenced E. coli levels during wet weather conditions. Nitrate + nitrite-N displayed a unique response to rain events compared with the other parameters, suggesting a different delivery route. Analyses of benthic macroinvertebrate communities were consistent with pollution trends. Collectively, these data suggest distinct agriculturally related E. coli contributions, as well as specific areas and practices for water quality improvement strategies. This study can serve as a resource for evaluating agricultural watersheds that are impaired for bacteria.

Positive Effects of Shade and Shelter Construction by Ants on Leafhopper-Ant Mutualism

Abstract The myrmecophilous five-spotted gamagrass leafhopper, Dalbulus quinquenotatus DeLong and Nault, and its tending ants on gamagrass Tripsacum dactyloides L. were examined to determine the influence of shade and ant-constructed shelters on the population sizes of D. quinquenotatus and ants. Gamagrass plants hosting ants and leafhoppers were exposed to 50, 30, or 0% artificially constructed shade. The greatest numbers of leafhoppers and ants were found on plants that received 50% shade. Shelters made by the ant Solenopsis geminata (F.) contained large numbers of leafhoppers and ants but were found only on T. dactyloides exposed to 50% shade in artificially constructed habitats. Additional sampling was conducted on wild gamagrass plants in the field to explore the presence of ants tending leafhoppers in shelters and to evaluate whether ant-constructed shelters protect leafhopper nymphs from parasitoid wasps. Large aggregations of S. geminata in shelters were also found in natural gamagrass habitats. Leafhopper nymphs living in shelters made by S. geminata may be protected against the dryinid wasp parasitoid Anteon ciudadi Olmi. No sheltered nymphs were parasitized by dryinids, whereas 24% of unsheltered nymphs had dryinid parasitism.

Geographic and Seasonal Variation in Size and Color of Adult Corn Leafhoppers (Hemiptera: Cicadellidae) from Mexico

Abstract We describe variation in wing length, head width, and color of the corn leafhopper, Dalbulus maidis (DeLong and Wolcott), in Mexico from 21 sites at nearctic and neotropical latitudes, from low (<700 m) and high (>700 m) elevations, and wet season (June) and irrigated dry season (October) maize habitats. Female and male D. maidis were collected from 21 sites located from 15.72° N to 25.48° N latitude and 2–1,203 m elevation. Females and males from the northern nearctic latitudes were larger and darker than leafhoppers from the southern Neotropical latitudes. Elevation did not affect the size or color of female or male leafhoppers. At an irrigated site where maize is cultivated all year (Colima), females and males collected in October had longer wings than leafhoppers collected in June. At a nonirrigated site (Zapopan) where maize is cultivated only in the wet season, females collected in June had longer wings, wider heads, and were darker than females collected in October. Compared with leafhoppers living in irrigated maize habitats, D. maidis from maize cultivated only in the wet season have significant variations in body size and color, suggesting D. maidis adapts to survive seasonal harsh environments.

Family-Level Benthic Macroinvertebrate Communities Indicate Successful Relocation and Restoration of a Northeast Iowa Stream

A major stream relocation and restoration project was started in 2004 near Dorchester, Iowa. The project converted riparian cropland and stream bank trees to native tallgrass prairie vegetation while relocating Brook Creek to its original streambed. The goal of this project was to restore Brook Creek to conditions comparable with South Pine Creek, a nearby reference coldwater stream that was used as a model for Brook Creek. Benthic macroinvertebrates were monitored in 2005, 2007, 2010, and 2012 in both Brook Creek and South Pine Creek. Benthic macroinvertebrate family-level taxonomic richness, Ephemeroptera/Plecoptera/Trichoptera (EPT) family richness, and family-level biotic indices (FBI) were calculated. We found that Brook Creek’s FBI values were lowered and EPT richness values increased significantly from 2005 to 2012, indicating establishment of a high quality benthic macroinvertebrate community. Benthic macroinvertebrate communities in Brook Creek became increasingly similar to South Pine Creek over the course of this study as evidenced by a principle component analysis and percent similarity, from a 28.72% similarity in 2005 to 62.54% similarity in 2012. These results demonstrate the successful reestablishment of a benthic macroinvertebrate assemblage following stream reconstruction and similarity to a high-quality reference stream.

New Distribution Records of Ground Beetles (Coleoptera: Carabidae) from Iowa and South Dakota, U.S.A.

The ground beetle (Coleoptera: Carabidae) fauna of the Central Plains has been recorded locally in occasional state lists (e.g. Kirk and Balsbaugh, 1975; Jaques and Redlinger, 1945), while additions have been reported mainly as a byproduct of other studies (e.g. Esau and Peters, 1975; Ellsbury et al., 1998). Further studies may reveal additional distribution record species and help refine habitat preferences (e.g. Larsen et al., 2003). Previously we have reported new state distribution records for 24 species of ground beetles from Iowa and three species from South Dakota (Purrington and Larsen, 1997; Purrington et al., 2000). During subsequent investigations, we have found an additional 12 species of ground beetles that according to Bousquet and Larochelle (1993) represent new state distribution records for either Iowa or South Dakota, and one additional species with a significant range expansion within South Dakota. All beetles were collected using standard pitfall trapping or light trapping techniques, or collected by hand. Several species were collected by hand after heavily treading moist litter amongst cattails growing on the edge of a marsh near Brookings, SD. Voucher specimens are deposited in the insect collection of the Hoslett Museum of Natural History at Luther College, Decorah, Iowa.

Rhamnus cathartica (Rosales: Rhamnaceae) Invasion Reduces Ground-Dwelling Insect Abundance and Diversity in Northeast Iowa Forests

ABSTRACT European buckthorn (Rhamnus cathartica L.) is an invasive woody shrub in deciduous forests of the Upper Midwest. Studies have suggested buckthorn invasion has negative effects on native plants, soil, and ecosystems, but its impacts on insects are largely unstudied. To test the impact of buckthorn invasion on ground-dwelling insects in forests of northeastern Iowa, pitfall traps were used to sample ground-dwelling insects at five sites four different periods from June to August 2013. Each site had three treatments: areas heavily infested with buckthorn, areas where buckthorn has not established, and areas where buckthorn had been removed within the past 2–10 yr. Most insects were identified to family and quantified; while ground beetles (Coleoptera: Carabidae) and ants (Hymenoptera: Formicidae) were identified to species and quantified. In total, 11,576 insects representing eight orders and 46 families were collected. Areas uninvaded by buckthorn had significantly greater insect abundance and taxonomic richness than areas invaded by buckthorn. Of the 948 ground beetles representing 40 species, abundance, species richness, and Shannon diversity indices were significantly lower in areas invaded by buckthorn compared with areas with no buckthorn. The 2,661 ants from 24 species had similar trends, but treatment differences were not significant because of high variability. These results clearly show a negative impact of buckthorn invasion on the abundance and taxonomic richness of ground-dwelling insects.