Original Abstract: Certain species play particularly large roles in ecosystems, and are often referred to as keystones. However, little is known about the interactive effects of these species where ...they co-occur. Prairie dogs (Cynomys spp.) and banner-tailed kangaroo rats Dipodomys spectabilis are commonly considered keystone species of grassland ecosystems, creating a mosaic of unique habitats on the landscape through ecosystem engineering and herbivory. We examined the separate and interactive effects of these species on the structure of grassland arthropod communities. We conducted a cross-site study at two locations in the northern Chihuahuan Desert, and evaluated the impacts of these rodents on ground-dwelling arthropod and grasshopper communities in areas where prairie dogs and kangaroo rats co-occurred compared to areas where each rodent species occurred alone. Our results demonstrate that prairie dogs (C. gunnisoni and C. ludovicianus) and banner-tailed kangaroo rats had keystone-level impacts on arthropod communities both separately and interactively. Their burrow systems provided important habitats for multiple trophic and taxonomic groups of arthropods, and increased overall arthropod abundance and species richness. Many arthropods also were attracted to the aboveground habitats around the mounds and across the landscapes where the rodents occurred. Detritivores, predators, ants, grasshoppers, and rare rodent burrow inhabitants were especially associated with prairie dog and kangaroo rat activity. The impacts of prairie dogs and kangaroo rats were unique, and the habitats they created supported different assemblages of arthropods. Where both rodent species co-occurred, there was greater heterogeneity and arthropod diversity on the landscape. Our results suggest that the interaction of multiple keystones, especially those with engineering roles, results in unique and more diverse communities in time and space. |l en
Recently, vector-borne diseases have been resurging in endemic areas and expanding their geographic range into nonendemic areas. Such changes have refocused attention to the potential for major ...public health events, as naive populations are exposed to these pathogens. Personal topical repellents, recommended by the United States Centers for Disease Control and Prevention and World Health Organization, remain a first line of protection against infection. The current study evaluated the repellent efficacy of four new U.S. Environmental Protection Agency-registered topical repellent products, two with picaridin as the active ingredient and two with IR3535, against a standard DEET (N,N-diethyl-3-methylbenzamide)-based product. All products were evaluated against a wide range of vector species under field conditions across the Americas. Human volunteers were used to evaluate product efficacy as compared with a well-known DEET-based formulation and determine suitability for use by the U.S. military. Findings demonstrated the new formulations performed as well as the standard U.S. military repellent and could be recommended for use.
A central concept in forensic entomology is that arthropod succession on carrion is predictable and can be used to estimate the postmortem interval (PMI) of human remains. However, most studies have ...reported significant variation in successional patterns, particularly among replicate carcasses, which has complicated estimates of PMIs. Several forensic entomology researchers have proposed that further integration of ecological and evolutionary theory in forensic entomology could help advance the application of succession data for producing PMI estimates. The purpose of this essay is to draw attention to the role of spatial aggregation of arthropods among carrion resources as a potentially important aspect to consider for understanding and predicting the assembly of arthropods on carrion over time. We review ecological literature related to spatial aggregation of arthropods among patchy and ephemeral resources, such as carrion, andwhenpossible integrate these results with published forensic literature. We show that spatial aggregation of arthropods across resources is commonly reported and has been used to provide fundamental insight for understanding regional and local patterns of arthropod diversity and coexistence. Moreover, two suggestions are made for conducting future research. First, because intraspecific aggregation affects species frequency distributions across carcasses, data from replicate carcasses should not be combined, but rather statistically quantified to generate occurrence probabilities. Second, we identify a need for studies that tease apart the degree to which community assembly on carrion is spatially versus temporally structured, which will aid in developing mechanistic hypotheses on the ecological factors shaping community assembly on carcasses.
We describe a weakly biomineralized non-trilobite artiopodan arthropod from the Guzhangian Weeks Formation of Utah. Falcatamacaris bellua gen. et sp. nov. is typified by a thin calcitic cuticle, ...broad cephalon without eyes or dorsal ecdysial sutures, an elongate trunk with distinctively sickle-shaped pleural spines and a long tailspine with a bifurcate termination. The precise affinities of Falcatamacaris gen. nov. are problematic due to the presence of unique features within Artiopoda, such as the peculiar morphology of the pleural and posterior regions of the trunk. Possible affinities with aglaspidid-like arthropods and concilitergans are discussed based on the possession of 11 trunk tergites, edge-to-edge articulations and overall body spinosity. The new taxon highlights the importance of the Weeks Formation Konservat-Lagerstaette for further understanding the diversity of extinct arthropod groups in the upper Cambrian.
Quickly, accurately, and easily assessing the efficacy of treatments to control sessile arthropods (e.g., scale insects) and stationary immature life stages (e.g., eggs and pupae) is problematic ...because it is difficult to tell whether treated organisms are alive or dead. Current approaches usually involve either maintaining organisms in the laboratory to observe them for development, gauging their response to physical stimulation, or assessing morphological characters such as turgidity and color. These can be slow, technically difficult, or subjective, and the validity of methods other than laboratory rearing has seldom been tested. Here, we describe development and validation of a quick easily used biochemical colorimetric assay for measuring the viability of arthropods that is sufficiently sensitive to test even very small organisms such as white fly eggs. The assay was adapted from a technique for staining the enzyme hexokinase to signal the presence of adenosine triphosphate in viable specimens by reducing a tetrazolium salt to formazan. Basic laboratory facilities and skills are required for production of the stain, but no specialist equipment, expertise, or facilities are needed for its use.
The expansion of urban areas is occurring globally, but not all city neighborhoods are gaining population. Because of economic decline and the recent foreclosure crisis, many U.S. cities are ...demolishing abandoned residential structures to create parcels of vacant land. In some cities, weak housing markets have, or will likely, recover in the near term, and these parcels will be redeveloped. However, in other cities, large numbers of abandoned parcels have no significant market value and no likelihood of near-term redevelopment. The creation of these vacated green spaces could offer opportunities to preserve declining species, restore ecosystem functions, and support diverse ecosystem services. Arthropods are an important indicator of the ability of urban vacant land to serve multiple functions, from conservation to food production. Across Europe, vacant lands have been found to support a diversity of rare species, and similar examinations of arthropods within this habitat are underway in the United States. In addition, using vacant land as a resource for local food production is growing rapidly worldwide. Arthropods play key roles in the sustainability of food production in cities, and land conversion to farming has been found to influence their community composition and function. A greater focus on quantifying the current ecological value of vacant land and further assessment of how changes in its ecosystem management affect biodiversity and ecosystem processes is clearly needed. Herein, we specifically focus on the role of arthropods in addressing these priorities to advance our ecological understanding of the functional role of vacant land habitats in cities.
Early successional ruderal plants in North America include numerous native and nonnative species, and both are abundant in disturbed areas. The increasing presence of nonnative plants may negatively ...impact a critical component of food web function if these species support fewer or a less diverse arthropod fauna than the native plant species that they displace. We compared arthropod communities on six species of common early successional native plants and six species of nonnative plants, planted in replicated native and nonnative plots in a farm field. Samples were taken twice each year for 2 yr. In most arthropod samples, total biomass and abundance were substantially higher on the native plants than on the nonnative plants. Native plants produced as much as five times more total arthropod biomass and up to seven times more species per 100 g of dry leaf biomass than nonnative plants. Both herbivores and natural enemies (predators and parasitoids) predominated on native plants when analyzed separately. In addition, species richness was about three times greater on native than on nonnative plants, with 83 species of insects collected exclusively from native plants, and only eight species present only on nonnatives. These results support a growing body of evidence suggesting that nonnative plants support fewer arthropods than native plants, and therefore contribute to reduced food resources for higher trophic levels.
A new arthropod, Haifengella corona new genus new species is described from the early Cambrian Chengjiang Lagerstaette (Series 2, Stage 3), Yunnan Province, southwest China. It is readily assignable ...to helmetiida based on gross morphology of the tergum. The new helmetiid is unique in having the marginal spines extending over one-third of the total body width. The weakly sclerotized tergum consists of six thoracic tergites with edge-to-edge tergite articulations. The sub-trapezoidal cephalic shield has a pair of long spines projecting from each posterolateral corner. A prehypostomal sclerite (anterior sclerite) recesses in the anterior margin of the cephalic shield, and a pair of bulges that are close to the prehypostomal sclerite in the cephalic shield are presumed to be the position of ventral eyes. Each of the thoracic tergites exhibits a pair of long spines projecting from the posterolateral corners. The semicircular pygidium carries one terminal spine and two pairs of lateral spines.
Not all studies have empirically supported the model that predicts a positive relationship between habitat heterogeneity and biodiversity. The authors hypothesized that these different results stem ...from the methods used to assess habitat heterogeneity; many studies used variables that are somewhat correlated in nature and measure 2 different features of the environment: the number of structure types (habitat heterogeneity) and the number of structures, disregarding their types (habitat amount). We tested this hypothesis with a single experiment that assigned orthogonal values of habitat heterogeneity and habitat amount to artificial environments located on the floor of a forest remnant. The results indicate that habitat heterogeneity had no significant effect on species richness, while habitat amount showed a positive effect when the number of individuals was not controlled. The authors conclude that conflicting results in previous tests of the heterogeneity model could stem from conceptual and methodological problems in experimental conception.
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