Short-horned grasshopper subfamilies feed at different rates on big bluestem and switchgrass cultivars

Grasshopper species belonging to subfamilies Melanoplinae, Gomphocerinae and Oedipodinae were tested for their feeding rate on three types of grass. All grasshopper species were offered Shawnee and Kanlow cultivars of switchgrass, Panicum virgatum L. and big bluestem, Andropogon gerardii Vitman. The grasshoppers, Melanoplus femurrubrum and Melanoplus differentialis were also tested for their feeding on turgid or wilted leaves of the Shawnee cultivar of switchgrass. We found that M. differentialis consumed more switchgrass compared to big bluestem while M. femurrubrum and Arphia xanthoptera consumed the most Shawnee switchgrass. The M. differentialis consumed more turgid grass compared to wilted switchgrass. The feeding performances show differences among grasshopper species even in the same subfamily and suggest that Melanoplinae grasshoppers may become destructive pests of switchgrass planted for biofuel production.

Short-horned grasshopper subfamilies feed at different rates on big bluestem and switchgrass cultivars

Grasshopper species belonging to subfamilies Melanoplinae, Gomphocerinae and Oedipodinae were tested for their feeding rate on three types of grass. All grasshopper species were offered Shawnee and Kanlow cultivars of switchgrass, Panicum virgatum L. and big bluestem, Andropogon gerardii Vitman. The grasshoppers, Melanoplus femurrubrum and Melanoplus differentialis were also tested for their feeding on turgid or wilted leaves of the Shawnee cultivar of switchgrass. We found that M. differentialis consumed more switchgrass compared to big bluestem while M. femurrubrum and Arphia xanthoptera consumed the most Shawnee switchgrass. The M. differentialis consumed more turgid grass compared to wilted switchgrass. The feeding performances show differences among grasshopper species even in the same subfamily and suggest that Melanoplinae grasshoppers may become destructive pests of switchgrass planted for biofuel production.

THE GRASSHOPPERS \u3ci\u3eARPHIA XANTHOPTERA\u3c/i\u3e AND \u3ci\u3eDICHROMORPHA VIRIDIS\u3c/i\u3e PREFER INTRODUCED SMOOTH BROME OVER OTHER GRASSES

A study of feeding preference was conducted on two tallgrass prairie grasshopper species, the autumn yellow-winged grasshopper Arphia xanthoptera (Burmeister) and the short-winged green grasshopper Dichromorpha viridis (Scudder), to determine if they would feed upon introduced grass species. Both grasshoppers were offered two non-native cool-season grasses, smooth brome (Bromus inermis Leyss) and Kentucky bluegrass (Poa pratensis L.), and two native warm-season grasses, big bluestem (Adropogon gerardii Vitman) and sideoats grama (Bouteloua curtipendula Michx.). Live biomass of the plants was weighed before and after feeding to quantify the amount of each plant species consumed by the grasshoppers. Statistical analysis showed that D. viridis strongly preferred smooth brome (P ≤ 0.05) over other species offered. A. xanthoptera also consumed more smooth brome than the other grass species offered. These results suggest that both grasshopper species accept non-native grasses and perhaps prefer them to tallgrass prairie species. Because the tallgrass prairie ecosystem of the Great Plains has been dramatically impacted by human activity, documentation of the response of native insects to incursion by exotic plants is important to preservation efforts. Moreover, if grasshoppers feed on invasive sod-forming species such as smooth brome and Kentucky bluegrass, they may become an important ally in maintaining native plant diversity in remnant grassland ecosystems

Zooplankton Density Increases in an Irrigation Reservoir During Drought Conditions

Harlan County Reservoir, located in south-central Nebraska, entered a drought in 2003, providing an opportunity to monitor the effects of drought on the zooplankton community in this irrigation reservoir. We sampled the zooplankton community at 15 standardized locations every other week from April through the third week of October from 2003-2011. Total zooplankton densities were higher (131.8 ±13.1 L-1) in drought reservoir conditions (2003-2006) than under normal conditions (66.6 ±9.0 L-1) (2007-2011). The zooplankton community was dominated by copepods throughout the study, with adult and immature (nauplii) copepods contributing 86.5% of the total zooplankton, while Daphnia spp. made up only 9.9%. Correlational analyses showed a positive relationship between total zooplankton, copepods and copepod nauplii and chlorophyll a and turbidity during normal reservoir conditions. Daphnia species showed a negative relationship with chlorophyll a during normal conditions and a negative relationship with turbidity in drought conditions. Our results document the dynamics of lower trophic levels during fluctuating water availability; such information will likely improve conservation and management of aquatic ecosystems during future episodes of changing environmental conditions

Current known range of the Platte River caddisfly, \u3ci\u3eIronoquia plattensis\u3c/i\u3e, and genetic variability among populations from three Nebraska Rivers

The Platte River caddisfly (Ironoquia plattensis Alexander and Whiles 2000) was recently described from a warm-water slough along the Platte River in central Nebraska and was considered abundant at the type locality. Surveys of 48 sites in 1999 and 2004 found eight additional sites with this species on the Platte River. The caddisfly was not found at the type locality in 2004 and one additional site in 2007, presumably because of drought conditions. Because of its apparent rarity and decline, the Platte River caddisfly is a Tier I species in Nebraska. For this project, surveys for the caddisfly were conducted at 113 new and original sites primarily along the Platte, Loup, and Elkhorn Rivers between 2009 and 2011. These surveys identified 30 new sites with the caddisfly. Larval densities were quantified at a subset of inhabited sites, and there was a large variation of densities observed. Seven sites on other Nebraska drainages were found to support morphologically similar caddisflies, presumably the Platte River caddisfly. Because of the discovery of populations outside the Platte River drainage, amplified fragment length polymorphism (AFLP) was used to determine the amount of genetic variability and breeding among sites on the Platte, Loup, and Elkhorn Rivers. Analysis of molecular variance (AMOVA) suggested moderate gene flow among the three river systems and that there was more genetic variation within populations than between populations. Differentiation, but not total divergence, was exhibited by the northernmost population from the Elkhorn River. Because it may be considered an indicator species and is vulnerable to ongoing habitat loss and degradation, all Platte River caddisfly populations should be conserved