Karl A. Roeder

Karl A. Roeder
United States Department of Agriculture | USDA · Agricultural Research Service (ARS)

PhD

About

30
Publications
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452
Citations

Publications

Publications (30)
Article
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Across the globe, temperatures are predicted to increase with consequences for many taxo-nomic groups. Arthropods are particularly at risk as temperature imposes physiological constraints on growth, survival, and reproduction. Given that arthropods may be disproportionately affected in a warmer climate-the question becomes which taxa are vulnerable...
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Ecologists search for rules by which traits dictate the abundance and distribution of species. Here we search for rules that apply across three common taxa of litter invertebrates in six North American forests from Panama to Oregon. We use image analysis to quantify the abundance and body size distributions of mites, springtails, and spiders in 21‐...
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• Theory suggests that performance increases with temperature up to an optimization point before rapidly decreasing as an animal approaches its upper thermal limit. Here, we use the red harvester ant, Pogonomyrmex barbatus, to test predictions about how daily temperature fluctuations and thermal tolerance combine to influence one metric of performa...
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The role plant diversity has played in regulating insect communities has been of interest for decades. Recent syntheses from agroecosystems suggest increasing plant diversity can positively affect beneficial insects like predators, reducing pest pressure and increasing yield. However, the agricultural landscape of the Midwestern United States is do...
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Western corn rootworm, Diabrotica virgifera virgifera, is one of the most economically important crop pests in the world with estimates of damage and control approximating over $1 billion USD annually. Despite an abundance of research devoted to studying rootworm biology in the central Corn Belt of the United States, key aspects on their thermal ec...
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Ants (Hymenoptera: Formicidae) are a conspicuous group of ectotherms whose behavior, distribution, physiology, and fitness are regulated by temperature. Consequently, interest in traits like thermal tolerance that enable ants to survive and thrive in variable climates has increased exponentially over the past few decades. Here, we synthesize the pu...
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1. Invasive species and habitat disturbance are among the most important drivers of biodiversity loss and ecological change. Their individual effects, however, are difficult to disentangle because invasion and disturbance are often intimately linked. Here we test alternative hypotheses to determine if the invasive red imported fire ant, Solenopsis...
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Changes in trophic niche-the pathways through which an organism obtains energy and nutrients-are a fundamental way in which organisms respond to environmental conditions. But the capacity for species to alter their trophic niches in response to global change, and the ways they do so when able, remain largely unknown. Here we examine food webs in th...
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Heat tolerance in insects is often considered invariant and used as a fixed trait in models predicting future distributions in a warming world. We show that heat tolerance of ants in a seasonal North American community is plastic in species active across multiple seasons. During the summer, these species could tolerate on average 6°C higher tempera...
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Aim In ectotherms, gradients of environmental temperature can regulate metabolism, development and ultimately fitness. The thermal adaptation hypothesis assumes that thermoregulation is costly and predicts that more thermally variable environments favour organisms with wider thermal ranges and thermal limits (i.e., critical thermal minima and maxim...
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Analyses of heat tolerance in insects often suggest that this trait is relatively invariant, leading to the use of fixed thermal maxima in models predicting future distribution of species in a warming world. Seasonal environments expose populations to a wide annual temperature variation. To evaluate the simplifying assumption of invariant thermal m...
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The establishment and spread of non-native species often results in negative impacts on biodiversity and ecosystem function. Several species of saltcedar, Tamarix spp. L., have been recently naturalized in large portions of the United States where they have altered plant and animal communities. To test the prediction that saltcedar negatively affec...
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Evidence for global insect declines mounts, increasing our need to understand underlying mechanisms. We test the nutrient dilution (ND) hypothesis—the decreasing concentration of essential dietary minerals with increasing plant productivity—that particularly targets insect herbivores. Nutrient dilution can result from increased plant biomass due to...
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For social organisms, foraging is often a complicated behavior where tasks are divided among numerous individuals. Here, we ask how one species, the red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae), collectively manages this behavior. We tested the Diminishing Returns Hypothesis, which posits that for social insects 1) for...
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In an era of rapid climate change, and with it concern over insect declines, we used two theories to predict 20‐year changes in 34 North American ant communities. The ecosystems, from deserts to hardwood forests, were first surveyed in the 1990s. When resurveyed in 2016‐2017 they averaged 1°C warmer with 200 gC/m2/y higher plant productivity. Ant c...
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1. To achieve numerical dominance, an ectotherm consumer requires a sizeable abiotic window in which it can forage. Here we explore how one abiotic factor, temperature, provides opportunity and regulates the impact of the invasive red imported fire ant, Solenopsis invicta, on an urban ant assemblage. 2. We first quantified S. invicta's ability to o...
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As ecosystems warm, ectotherm consumer activity should also change. Here we use principles from metabolic and thermal ecology to explore how seasonal and diel temperature change shapes a prairie ant community's foraging rate and its demand for two fundamental resources: salt and sugar. From April through October 2016 we ran transects of vials fille...
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Natural disturbances can occur stochastically with profound impacts on fauna and flora. Here we quantified the impact of a one in 100-yr flood on terrestrial invertebrate communities in south central Oklahoma. Before the flood, we observed 4,082 individuals from 92 species weighing a total of 18.61 g that belonged to compositionally different above...
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Big-headed ants from the genus Pheidole (Hymenoptera: Formicidae) are diverse and ecologically important worldwide. Here we report the first record in Oklahoma for two species, Pheidole pelor and Pheidole tysoni, increasing the number of known Pheidole species in Oklahoma to twelve. We highlight two areas, northwestern and southeastern Oklahoma, th...
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Populations may collectively exhibit a broad diet because individuals have large diet breadths and/or because subpopulations of specialists co-occur. In social insect populations, the diet of the genetic individual—the colony—may similarly arise because workers are diet generalists or castes of specialists. We used elemental and isotopic methods to...
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Nitrogen and phosphorus frequently limit terrestrial plant production, but have a mixed record in regulating the abundance of terrestrial invertebrates. We contrasted four ways that Na could interact with an NP fertilizer to shape the plants and invertebrates of an inland prairie. We applied NP and Na to m(2) plots in a factorial design. Abovegroun...
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We present a checklist of 47 ant species (Hymenoptera: Formicidae) from the Wichita Mountains Wildlife Refuge in Oklahoma, USA. Surveys conducted in 2015 recaptured 67% of all historically collected species and add 12 new county records including the new state records of Pheidole tetra and Solenopsis aurea. We demonstrate the importance of sampling...
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We report the first record of the Pseudomyrmecinae subfamily of ants in Oklahoma. Eleven species have been recorded from the Nearctic region, primarily in southern or coastal areas. This collection increases the known distribution northward into the central United States for one of those species, Pseudomyrmex pallidus.
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We report the first record of the ant genus Leptogenys in Oklahoma. Two species have been recorded from the United States, but northern range boundaries for both have been primarily limited to Gulf Coast states. This collection increases the known distribution northward into the central United States for one of those species, Leptogenys elongata (B...
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Food protein-carbohydrate content has significant consequences for animal survival, growth and reproduction. Rarely, though, is its effect examined over an animal's entire lifetime. In this study we reared newly hatched caterpillars (Heliothis virescens Fabricus (Lepidoptera: Noctuidae)) on diets containing different protein-carbohydrate (p:c) rati...
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Controlling microbial growth in artificial diets is a key component in the rearing of laboratory insects. In this study an antimicrobial agent, Diet Antimicrobial Agent (DAA), was tested for its ability to suppress microbial growth on a range of different diets, and for its effect on larval and pupal performance of individuals from two different st...
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Westwoodia (Ichneumonidae: Ctenopelmatinae) is an Australian endemic heretofore known from only two described species. Three additional species are described here: Westwoodia gauldi Wharton and Roeder, n. sp. and W. romani Wharton and Roeder, n. sp., both from southeastern Australia, and W. rodmani Wharton and Roeder, n. sp. from western Australia....

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