Interactions among species and ecosystems determine their responses to scale-specific fluctuations

Ecosystems are highly connected systems with many interacting components. Understanding the mechanisms creating ecosystem patterns requires an explicit consideration of the scales at which interactions among species and their environments occur. This dissertation focuses on the scale of temporal variability and how temporal variability is incorporated into communities’ dynamics. I first derive an abstract theory that describes the general patterns of variability propagation within communities. Next, I explore the role of species’ interaction strengths on community dynamics across time scales. Finally, I study the impact of human-induced hydrological changes of the Guadalquivir River on the European anchovy fishery in the Gulf of Cadiz.Chapter 1 uses linear response theory to extend the top down and bottom up views of ecology across time scales. Specifically, I study a tri-trophic food chain and how fluctuations in productivity filter up the food chain. I find that variability follows the pattern predicted by top-down equilibrium-based theories at slow time scales. However, at an intermediate time scale, consumers can both decrease and increase the sensitivity of lower trophic levels to variability. For example, perturbations at intermediate frequencies can excite the endogenous cycles of a community leading to resonance. Only at the fastest time scales do top down effects begin to break down as variability becomes dampened at higher trophic levels. This theory provides a robust new framework to interpret food web patterns resulting from resource pulses and other bottom up perturbations. Chapter 2 combines the metabolic theory of ecology and empirical information of consumer-resource interactions to ground the general theory developed in Chapter 1. Body size is not only a significant determinant of vital rates and but also species interaction strengths. This approach allows me to focus on biologically relevant parameter space. I predict that predators can control herbivores and producers\u27 variability at a time scale of days to years. This theory predicts that indirect effects actively shape communities\u27 responses across a wide range of ecologically relevant time scales. Finally, in Chapter 3, I explore the relationship between ecology and society by studying how agricultural water use is connected to the marine anchovy fishery in Spain’s Gulf of Cadiz. Using time series analysis, I explore the correlations between hydrology, the estuarine community, and anchovy recruitment to the Gulf of Cadiz. The Guadalquivir river’s mean annual discharge and seasonality have decreased over the last 90 years due to increasing river regulation and extraction. European anchovies use the river estuary as a nursery. These hydrological changes have reduced anchovy recruitment to the Gulf of Cadiz, connecting terrestrial water use with the marine fishery. I then produce a water allocation theory for terrestrial agriculture and a marine fishery. I predict that even practices that improve water efficiency will not necessarily prevent terrestrial ecosystems from total water consumption. I find that the protection of downriver ecosystem services is only protected when the benefits to marine ecosystems are considered nonsubstitutable with terrestrial ecosystems. The issue of scale – ecological and spatiotemporal – is at the heart of my thesis. My first chapter shows that the percolation of variability is not invariant across time scales. In my second chapter, I predict how body size drives differences in community responses to variability. These theories can provide new insights into how variability impacts communities. Finally, in my last chapter, I explore rivers and migration can create trade-offs between seemingly isolated ecosystems

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe

Observation of tW production in the single-lepton channel in pp collisions at root s=13 TeV

A measurement of the cross section of the associated production of a single top quark and a W boson in final states with a muon or electron and jets in proton-proton collisions at root s = 13 TeV is presented. The data correspond to an integrated luminosity of 36 fb(-1) collected with the CMS detector at the CERN LHC in 2016. A boosted decision tree is used to separate the tW signal from the dominant t (t) over bar background, whilst the subleading W+jets and multijet backgrounds are constrained using data-based estimates. This result is the first observation of the tW process in final states containing a muon or electron and jets, with a significance exceeding 5 standard deviations. The cross section is determined to be 89 +/- 4 (stat) +/- 12 (syst) pb, consistent with the standard model.Peer reviewe

Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV

A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV

Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at root s=13 TeV

Abstract:A measurement of the top quark mass is performed using a data sample en-riched with single top quark events produced in thetchannel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb−1, recorded at√s= 13TeV by the CMS experiment at the LHC in 2016. Candidate events are selectedby requiring an isolated high-momentum lepton (muon or electron) and exactly two jets,of which one is identified as originating from a bottom quark. Multivariate discriminantsare designed to separate the signal from the background. Optimized thresholds are placedon the discriminant outputs to obtain an event sample with high signal purity. The topquark mass is found to be172.13+0.76−0.77GeV, where the uncertainty includes both the sta-tistical and systematic components, reaching sub-GeV precision for the first time in thisevent topology. The masses of the top quark and antiquark are also determined separatelyusing the lepton charge in the final state, from which the mass ratio and difference aredetermined to be0.9952+0.0079−0.0104and0.83+1.79−1.35GeV, respectively. The results are consistentwithCPTinvariance

Search for a heavy Higgs boson decaying into two lighter Higgs bosons in the tau tau bb final state at 13 TeV

A search for a heavy Higgs boson H decaying into the observed Higgs boson h with a mass of 125 GeV and another Higgs boson h(S) is presented. The h and h(S) bosons are required to decay into a pair of tau leptons and a pair of b quarks, respectively. The search uses a sample of proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137 fb(-1). Mass ranges of 240-3000 GeV for m(H) and 60-2800 GeV for m(hS) are explored in the search. No signal has been observed. Model independent 95% confidence level upper limits on the product of the production cross section and the branching fractions of the signal process are set with a sensitivity ranging from 125 fb (for m(H) = 240 GeV) to 2.7 fb (for m(H) = 1000 GeV). These limits are compared to maximally allowed products of the production cross section and the branching fractions of the signal process in the next-to-minimal supersymmetric extension of the standard model.Peer reviewe

Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at root s=5.02 TeV Using Leptonic Decays

The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb(-1). Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as sigma(WW) = 37:0(-5.2)(+5.5) (stat)(-2.6)(+2.7) (syst) pb, sigma(WZ) = 6.4(-2.1)(+2.5) (stat)(-0.3)(+0.5)(syst) pb, and sigma(ZZ) = 5.3(-2.1)(+2.5)(stat)(-0.4)(+0.5) (syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy

Theoretical and experimental studies on behavioral syndromes in aphids

Individuals’ behaviors can be correlated across time and contexts, in a phenomenon now known as behavioral syndromes. Using an experimental approach, I demonstrate that genetically identical pea aphids are highly repeatable in multiple behavioral traits, however these behaviors are uncorrelated. Then using a state variable model I show that asymmetries in size can maintain a hierarchy between least and most bold individuals in foraging intensity across development. However, individuals that complete compensatory growth show an inversion in the rank-order of foraging activity between early and late development (ie individuals that are the boldest early in life are less bold than their “timid” counterparts late in life). In conclusion, I demonstrate both theoretically and empirically that non-genetic differences are capable of explaining repeatability in the expression of a single behavior; however I found no evidence that non-genetic mechanisms can correlations between multiple behaviors