Scalar Field Theories with Polynomial Shift Symmetries

We continue our study of naturalness in nonrelativistic QFTs of the Lifshitz type, focusing on scalar fields that can play the role of Nambu-Goldstone (NG) modes associated with spontaneous symmetry breaking. Such systems allow for an extension of the constant shift symmetry to a shift by a polynomial of degree $P$ in spatial coordinates. These "polynomial shift symmetries" in turn protect the technical naturalness of modes with a higher-order dispersion relation, and lead to a refinement of the proposed classification of infrared Gaussian fixed points available to describe NG modes in nonrelativistic theories. Generic interactions in such theories break the polynomial shift symmetry explicitly to the constant shift. It is thus natural to ask: Given a Gaussian fixed point with polynomial shift symmetry of degree $P$, what are the lowest-dimension operators that preserve this symmetry, and deform the theory into a self-interacting scalar field theory with the shift symmetry of degree $P$? To answer this (essentially cohomological) question, we develop a new graph-theoretical technique, and use it to prove several classification theorems. First, in the special case of $P=1$ (essentially equivalent to Galileons), we reproduce the known Galileon $N$-point invariants, and find their novel interpretation in terms of graph theory, as an equal-weight sum over all labeled trees with $N$ vertices. Then we extend the classification to $P>1$ and find a whole host of new invariants, including those that represent the most relevant (or least irrelevant) deformations of the corresponding Gaussian fixed points, and we study their uniqueness.Comment: 70 pages. v2: minor clarifications, typos corrected, a reference adde

Physiological Ecology of Overwintering and Cold-Adapted Arthropods

Given their abundance and diversity, arthropods are an excellent system to investigate biological responses to winter. Winter conditions are being majorly impacted by climate change, and therefore understanding the overwintering biology of arthropods is critical for predicting ecological responses to climate change. In Chapters 2 and 3, I investigate the winter biology of a winter-active wolf spider. I show that winter-active spiders can take advantage of periodic prey resources and grown in the winter, which may allow them to get a jumpstart on spring reproduction. I also investigate spiders’ ability to track changes in their environment by quantifying low temperature thresholds associated with simulated winter warming and show that winter warming may make spiders more susceptible to extreme cold events. In Chapter 4, I address ecological factors that influence the distribution of an Antarctic insect, showing that population density is primarily regulated by the availability of suitable habitat. Finally, I designed a laboratory module for an introductory science course that incorporates principles of phenotypic plasticity and climate change to illustrate biological responses to climate change. Taken together, these studies improve our understanding of the overwintering physiology and ecology of arthropods, with wide applications including biological control, spatial ecology, and pedagogy

Is Everything Connected? Following the Predators, Pests, and Plants Within a No-Till, Western Montana Agroecosystem

Agricultural systems are being re-engineered with hedgerows, living mulches, or minimum tillage activities in hopes of retaining populations of beneficial, predatory insects that may decrease the need for pesticide use. The purpose of this research was twofold. First, this on-farm research assessed the population and activity of six beneficial arthropod predators - the carabid beetle (Carabidae: Coleoptera), minute pirate bug (Orius spp.: Hemiptera), nabid bug (Nabis spp.: Hemiptera), lady beetle larvae (family Coccinellidae: Coleoptera), syrphid fly larvae (Syrphidae: Diptera) and spiders (Araneae) - and one crop pest - the imported cabbage worm (Pieris rapae: Lepidoptera) - within a no-till Brussels sprouts (Brassica oleracea, gemmifera group) and red clover (Trifolium pratense) living-mulch system. Second, using two common organic insecticides - Bacillus thuringiensis var. kurstaki (Bt) and a pyrethrin/rotenone blend – this research assessed the capacity of these aforementioned predatory or parasitic arthropods to control the P. rapae population and crop damage through biological (as compared to chemical) means. Field investigations for predators/pests involved weekly sweep-net sampling, pitfall trap installation, and direct plant examination. Insecticides were applied as a bi-weekly “calendar” application (pyrethrin/rotenone) or as a pest-density “threshold” dependant application (Bt). Generally, pest control and damage prevention were more successful in Bt treatments than in pyrethrin/rotenone treatments. Bt pesticides had no significant effect on any arthropods sampled, while the pyrethrin/rotenone insecticide appeared to significantly reduce the activity or population levels of all arthropods sampled. P. rapae activity and crop damage was lowest in Bt treated plots, moderate in control plots (no pesticides were applied, yet natural levels of arthropods were present) , and highest in plots treated with pyrethrin/rotenone sprays. Preliminary results indicate that Bt treatments worked as an additive control measure, which then augmented natural predator populations. The increased pest activity and damage in pyrethrin/rotenone treated plots - which coincided with reduced “beneficial” insect numbers as compared to the other treatments - may indicate a disruption of the multiple-arthropod predator assemblage that kept pest impacts lower in the “control” plots

Interactions Among Top-down Regulators in a Temperate Forest Floor Ecosystem;Effects on Macrofauna, Mesofauna, Microbes and Litter Decay

High species diversity and complexity of forest-floor food webs present a challenge for understanding the role of species interactions (e.g. competition and predation) as regulatory mechanisms for ecosystem processes such as decomposition and nutrient cycling. In particular, we understand very little about the roles of forest-floor predators in regulating diversity and abundance of lower trophic levels and ecosystem processes. However, ecological theory and several studies suggest that interactions among intraguild predators (IGP) may be important controls of diversity and abundance of organisms and detritus in lower trophic levels within food webs. A key prediction is that interactions among predators weaken trophic cascades. My research examined this prediction by characterizing interactions among predators and examining their effects on lower trophic levels within the forest-floor food web of Northeast Ohio. The results of the laboratory microcosm studies, in combination with several previous studies, suggest that the effects of removal treatment on intraguild predators, especially centipedes, spiders, carabid beetles, and salamander, were not the result of intraguild predation, but were more likely to have been the result of non-consumptive competitive interactions (NCEs). Predator removal from open, unrestricted field plots resulted in changes in the abundances of several groups of predators and macrodetritivores. Additionally, I found that predator manipulation affected composition of microflora within the soils at my field site. The mechanisms for this effect remain uncertain but may be indicative of antibiotic interactions within the soil through bacteria dispersed through skin secretions and feces of predators, particularly salamanders. This work contributes significantly to a growing body of evidence indicating that territorial predators, such as P. cinereus, which are constrained to spatially fixed microhabitats, can be strong regulators of guild members and lower trophic levels. My results also supp

Fear and Loathing in the Super Organism: Foraging Strategy Doesn\u27t Change Forager Response in a Landscape of Fear.

Understanding how predators impact keystone species, like ants, is very important for our understanding of ecology because of ants\u27 importance in shaping community dynamics and ecosystem functions. In this thesis I present research investigating the role of the ant-specialized spider Anasaitis canosa in influencing the foraging behavior of four ant species (Formica pallidefulva, Odontomachus ruginodis, Pheidole obscurithorax & Solenopsis invicta). Collectively, these four species use foraging strategies exhibited by most ants. I conducted two experiments to quantify the impacts of spider predation on ant prey. The first used forty colonies of four ant species to investigate how A. canosa changed foraging behavior at both the individual and colony level. The second used 27 lab-reared S. invicta colonies to see if there was any evidence for innate predatory avoidance in foragers and if predatory avoidance was influenced by learning. A field study observed the density and prey choices of A. canosa in 3 sites within the UCF arboretum. In sum, no consistent change in foraging occurred in the presence of A. canosa, over time scales sufficient to detect colony-level impacts and thus colonies as a whole appear to be risk insensitive. Naïve colonies had more ants beginning foraging before a single ant would return in their first trial compared to the second trial. This suggests forager learning occurs as foragers respond to the perception of a predator, and that S. invicta can reduce individual risk through increasing forager numbers. A. canosa predation rates and density were calculated and based on these estimates an approximate impact upon a colony was made. Most importantly, 13 foragers/m2 inside each foraging cohort can be expected to have prior experience with the spider

Sensitivity and Tolerance of Riparian Arthropod Communities to Altered Water Resources along a Drying River

abstract: Background Rivers around the world are drying with increasing frequency, but little is known about effects on terrestrial animal communities. Previous research along the San Pedro River in southeastern AZ, USA, suggests that changes in the availability of water resources associated with river drying lead to changes in predator abundance, community composition, diversity, and abundance of particular taxa of arthropods, but these observations have not yet been tested manipulatively. Methods and Results In this study, we constructed artificial pools in the stream bed adjacent to a drying section of the San Pedro River and maintained them as the river dried. We compared pitfall trapped arthropods near artificial pools to adjacent control sites where surface waters temporarily dried. Assemblage composition changed differentially at multiple taxonomic levels, resulting in different assemblages at pools than at control sites, with multiple taxa and richness of carabid beetle genera increasing at pools but not at controls that dried. On the other hand, predator biomass, particularly wolf spiders, and diversity of orders and families were consistently higher at control sites that dried. These results suggest an important role for colonization dynamics of pools, as well as the ability of certain taxa, particularly burrowing wolf spiders, to withstand periods of temporary drying. Conclusions Overall, we found some agreement between this manipulative study of water resources and a previous analysis of river drying that showed shifts in composition, changes in diversity, and declines in abundance of certain taxa (e.g. carabid beetles). However, colonization dynamics of pools, as well as compensatory strategies of predatory wolf spiders seem to have led to patterns that do not match previous research, with control sites maintaining high diversity, despite drying. Tolerance of river drying by some species may allow persistence of substantial diversity in the face of short-term drying. The long-term effects of drying remain to be investigated.The article is published at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.010927

Sensitivity and Tolerance of Riparian Arthropod Communities to Altered Water Resources along a Drying River

Rivers around the world are drying with increasing frequency, but little is known about effects on terrestrial animal communities. Previous research along the San Pedro River in southeastern AZ, USA, suggests that changes in the availability of water resources associated with river drying lead to changes in predator abundance, community composition, diversity, and abundance of particular taxa of arthropods, but these observations have not yet been tested manipulatively