A Comparison of the Effectiveness of Pitfall Traps and Winkler Litter Samples for Characterization of Terrestrial Ant (Formicidae) Communities in Temperate Savannas

Relatively few studies in temperate environments have compared pitfall traps and Winkler litter samples, two of the most commonly used ant (Formicidae) sampling protocols. Most of the comparative work has been performed in tropical and subtropical environments. Temperate studies have primarily taken place in forested environments. Our study focuses on the relative efficiency of these two methods in temperate oak savannas, the major ecotone connecting grasslands and deciduous forest in the Midwest. These environments are often maintained by fire and mechanical brush removal, which tends to decrease the amount of available leaf litter. We sampled 21 sites, varying in age since restoration from un-restored to 22 years of restoration activities in McHenry Co. Illinois. Each site was sampled with 30 pitfall traps and five Winkler litter samples. A total of 38 species in 17 genera in 5 subfamilies were captured and identified. Pitfall traps accounted for 37 of the species, while Winkler litter samples only captured 23 species, and only one species specific to that method. We conclude that in northern temperate savannas, pitfall traps were more effective and more efficient at characterizing the epigeic ant community than Winkler litter samples

A Comparison of the Effectiveness of Pitfall Traps and Winkler Litter Samples for Characterization of Terrestrial Ant (Formicidae) Communities in Temperate Savannas

Relatively few studies in temperate environments have compared pitfall traps and Winkler litter samples, two of the most commonly used ant (Formicidae) sampling protocols. Most of the comparative work has been performed in tropical and subtropical environments. Temperate studies have primarily taken place in forested environments. Our study focuses on the relative efficiency of these two methods in temperate oak savannas, the major ecotone connecting grasslands and deciduous forest in the Midwest. These environments are often maintained by fire and mechanical brush removal, which tends to decrease the amount of available leaf litter. We sampled 21 sites, varying in age since restoration from un-restored to 22 years of restoration activities in McHenry Co. Illinois. Each site was sampled with 30 pitfall traps and five Winkler litter samples. A total of 38 species in 17 genera in 5 subfamilies were captured and identified. Pitfall traps accounted for 37 of the species, while Winkler litter samples only captured 23 species, and only one species specific to that method. We conclude that in northern temperate savannas, pitfall traps were more effective and more efficient at characterizing the epigeic ant community than Winkler litter samples

Is It Easy to Be Urban? Convergent Success in Urban Habitats among Lineages of a Widespread Native Ant

The most rapidly expanding habitat globally is the urban habitat, yet the origin and life histories of the populations of native species that inhabit this habitat remain poorly understood. We use DNA barcoding of the COI gene in the widespread native pest ant Tapinoma sessile to test two hypotheses regarding the origin of urban populations and traits associated with their success. First, we determine if urban samples of T. sessile have a single origin from natural populations by looking at patterns of haplotype clustering fromacross their range. Second, we examine whether polygynous colony structure - a trait associated with invasion success - is correlated with urban environments, by studying the lineage dependence of colony structure. Our phylogenetic analysis of 49 samples identified four well supported geographic clades. Within clades, Kimura-2 parameter pairwise genetic distances revealed \u3c2.3% variation; however, between clade genetic distances were 7.5-10.0%, suggesting the possibility of the presence of cryptic species. Our results indicate that T. sessile has successfully colonized urban environments multiple times. Additionally, polygynous colony structure is a highly plastic trait across habitat, clade, and haplotype. In short, T. sessile has colonized urban habitats repeatedly and appears to do so using life history strategies already present in more natural populations. Whether similar results hold for other species found in urban habitats has scarcely begun to be considered

Trophic ecology of the invasive argentine ant: spatio-temporal variation in resource assimilation and isotopic enrichment

Studies of food webs often employ stable isotopic approaches to infer trophic position and interaction strength without consideration of spatio-temporal variation in resource assimilation by constituent species. Using results from laboratory diet manipulations and monthly sampling of field populations, we illustrate how nitrogen isotopes may be used to quantify spatio-temporal variation in resource assimilation in ants. First, we determined nitrogen enrichment using a controlled laboratory experiment with the invasive Argentine ant (Linepithema humile). After 12 weeks, worker δ15N values from colonies fed an animal-based diet had δ15N values that were 5.51% greater compared to colonies fed a plant-based diet. The shift in δ15N values in response to the experimental diet occurred within 10 weeks. We next reared Argentine ant colonies with or without access to honeydew-producing aphids and found that after 8 weeks workers from colonies without access to aphids had δ15N values that were 6.31% larger compared to colonies with access to honeydew. Second, we sampled field populations over a 1-year period to quantify spatio-temporal variability in isotopic ratios of L. humile and those of a common native ant (Solenopsis xyloni). Samples from free-living colonies revealed that fluctuations in δ15N were 1.6–2.4‰ for L. humile and 1.8–2.9‰ for S. xyloni. Variation was also detected among L. humile castes: time averaged means of δ15N varied from 1.2 to 2.5‰ depending on the site, with δ15N values for queens ≥ workers > brood. The estimated trophic positions of L. humile and S. xyloni were similar within a site; however, trophic position for each species differed significantly at larger spatial scales. While stable isotopes are clearly useful for examining the trophic ecology of arthropod communities, our results suggest that caution is warranted when making ecological interpretations when stable isotope collections come from single time periods or life stages

Is It Easy to Be Urban? Convergent Success in Urban Habitats among Lineages of a Widespread Native Ant

The most rapidly expanding habitat globally is the urban habitat, yet the origin and life histories of the populations of native species that inhabit this habitat remain poorly understood. We use DNA barcoding of the COI gene in the widespread native pest ant Tapinoma sessile to test two hypotheses regarding the origin of urban populations and traits associated with their success. First, we determine if urban samples of T. sessile have a single origin from natural populations by looking at patterns of haplotype clustering from across their range. Second, we examine whether polygynous colony structure – a trait associated with invasion success – is correlated with urban environments, by studying the lineage dependence of colony structure. Our phylogenetic analysis of 49 samples identified four well supported geographic clades. Within clades, Kimura-2 parameter pairwise genetic distances revealed <2.3% variation; however, between clade genetic distances were 7.5–10.0%, suggesting the possibility of the presence of cryptic species. Our results indicate that T. sessile has successfully colonized urban environments multiple times. Additionally, polygynous colony structure is a highly plastic trait across habitat, clade, and haplotype. In short, T. sessile has colonized urban habitats repeatedly and appears to do so using life history strategies already present in more natural populations. Whether similar results hold for other species found in urban habitats has scarcely begun to be considered

Frequent Long-Range Epigenetic Silencing of Protocadherin Gene Clusters on Chromosome 5q31 in Wilms' Tumor

Wilms' tumour (WT) is a pediatric tumor of the kidney that arises via failure of the fetal developmental program. The absence of identifiable mutations in the majority of WTs suggests the frequent involvement of epigenetic aberrations in WT. We therefore conducted a genome-wide analysis of promoter hypermethylation in WTs and identified hypermethylation at chromosome 5q31 spanning 800 kilobases (kb) and more than 50 genes. The methylated genes all belong to α-, β-, and γ-protocadherin (PCDH) gene clusters (Human Genome Organization nomenclature PCDHA@, PCDHB@, and PCDHG@, respectively). This demonstrates that long-range epigenetic silencing (LRES) occurs in developmental tumors as well as in adult tumors. Bisulfite polymerase chain reaction analysis showed that PCDH hypermethylation is a frequent event found in all Wilms' tumor subtypes. Hypermethylation is concordant with reduced PCDH expression in tumors. WT precursor lesions showed no PCDH hypermethylation, suggesting that de novo PCDH hypermethylation occurs during malignant progression. Discrete boundaries of the PCDH domain are delimited by abrupt changes in histone modifications; unmethylated genes flanking the LRES are associated with permissive marks which are absent from methylated genes within the domain. Silenced genes are marked with non-permissive histone 3 lysine 9 dimethylation. Expression analysis of embryonic murine kidney and differentiating rat metanephric mesenchymal cells demonstrates that Pcdh expression is developmentally regulated and that Pcdhg@ genes are expressed in blastemal cells. Importantly, we show that PCDHs negatively regulate canonical Wnt signalling, as short-interfering RNA–induced reduction of PCDHG@ encoded proteins leads to elevated β-catenin protein, increased β-catenin/T-cell factor (TCF) reporter activity, and induction of Wnt target genes. Conversely, over-expression of PCDHs suppresses β-catenin/TCF-reporter activity and also inhibits colony formation and growth of cancer cells in soft agar. Thus PCDHs are candidate tumor suppressors that modulate regulatory pathways critical in development and disease, such as canonical Wnt signaling

Climate mediates the effects of disturbance on ant assemblage structure

Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about howclimate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effectwas manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk. © 2015 The Author(s) Published by the Royal Society. All rights reserved

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p&lt;0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5–5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p&lt;0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4–10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p&lt;0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32–4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP &gt;5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification

Predicting Argentine ant (Linepithema humile) invasions at multiple spatial scales : the relative importance of abiotic and biotic factors

A prominent and unresolved question in ecology concerns why communities differ in their susceptibility to invasion. A complete knowledge of this issue will only result from an understanding of how biotic interactions and abiotic suitability interact with one another and change in importance across spatial scales. Factors important in determining the spread of invasive species at the community scale, such as local environmental conditions and biotic resistance, may be completely different from the factors that determine occurrence at the regional or global scale. Argentine ants (Linepithema humile) are an ecologically and economically damaging species that have been spread globally. Strongly competitive species such as this, are predicted to be more limited by abiotic than by biotic factors, but this prediction has rarely been tested. In Chapter 1 I use manipulative field experiments to demonstrate that abiotic factors (elevated soil moisture levels) increased both the abundance of Argentine ants and their ability to invade native ant communities. Using a factorial field experiment, in Chapter 2 I show that biotic resistance from native ants was unimportant and abiotic factors were preeminent in determining invasion success. Interestingly, an analysis of similar variables at the landscape scale revealed that Argentine ant occurrence was not correlated with precipitation. Through the application of predictive distribution models for Argentine ants across southern California, I demonstrate in Chapter 3 that insufficient sampling of environmental parameters leads to incorrect predictions of their distribution. Also, in multiple variable models, environmental variables differed in their relative importance across regions and spatial grain. The results of this dissertation are of general interest for several reasons. First, they demonstrate that fine-scale differences in the physical environment can eclipse biotic resistance from native competitors in determining community susceptibility to invasion. Second, this research illustrates surprising complexities with respect to how the abiotic factors limiting invasion success change in importance with spatial scale. Lastly, my results suggest that it is essential to account for the sufficiency of sampling when creating predictive distribution models and that it is important to use variables that are meaningful with respect to the spatial resolution of the data being analyze

Lizard community structure across a grassland - creosote bush ecotone in the Chihuahuan Desert

I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland - creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jomada del Muerto basin has increased dramatically in the past 150 years because of the rapid spread of creosote bush. I asked four related questions: how large and where is the ecotone based on vegetative structure, and do lizard abundance and diversity change across the ecotone? Vegetation data were analyzed using discriminate function analysis to determine the extent of the ecotone. Changes in lizard abundance across the ecotone were analyzed by analysis of variance. During two summers, 677 individual lizards of 9 genera and 12 species were captured. Lizard abundance increased with increasing distance from the ecotone and was similar in grassland and creosote bush habitat. Grasslands had higher species richness than both the creosote bush and ecotone habitats. Grassland sites had greater habitat heterogeneity than did creosote bush sites. No ecotone specialist species were detected, and all common lizard species could be found in each habitat. Three potential explanations for decreased abundance in the ecotone are presented: (1) increased risk of predation, (2) decreased prey abundance, and (3) lack of species-specific microhabitat requisites