Parsing the Particulars of Pollination: Ecological and Anthropogenic Drivers of Plant and Pollinator Dynamics

My research focuses on wild pollinating insects and the external influences on their population dynamics in both natural and human altered settings. Pollination from wild insects (e.g. wild bees, flies, butterflies, etc.) is critically important for both agricultural systems and the maintenance of wild/native plant biodiversity. Unfortunately, similarly to honey bees, numerous wild pollinating insects are experiencing global declines in abundance and diversity. Causes for the declines are varied and far reaching with mounting evidence showing these declines manifest in both, natural and human altered environments. Accordingly, the declines in pollinator health will have similarly widespread consequences, posing a precipitous threat to biodiversity, food production, and economic stability. The breadth and severity of the global pollinator decline highlights the need to develop a thorough understanding of how wild pollinators interface with their environments in both natural and human altered settings. Specifically, my research aims to help elucidate the drivers of natural plant and pollinator dynamics as well as the causes of wild pollinator decline utilizing comprehensive interwoven empirical and theory-based approaches. The first half of this thesis investigates the effects of urban development on wild bee communities using urban gardens as study sites in southeastern Michigan. My colleagues and I developed a large-scale multi-faceted research project sampling thousands of bees and numerous environmental variables across our sites. Results described in chapter two reveal that the negative effects of urban development on ground nesting bumble bees are driven entirely by declines in females while males show no response to urbanization. It also details a surprisingly abundant bumble bee population in the city of Detroit MI. Chapter three expands focus to the entire sampled set of bees and shows that the differential effect of urban development on females and males is apparent in all sampled ground nesting bees groupings. However, wild bees which nest in above-ground cavities have positive correlations with urban development. Chapter four uses US census data to investigate how socioeconomic conditions in urban settings can influence the location and floral quality of our study sites, urban gardens. The second half examines wild plant and pollinator dynamics in natural settings using theoretical models informed by empirical data and observations. Chapter five investigates the direct and indirect effects of insect herbivores on pollination in a community context. When attacked by herbivores, plants mount chemical defenses which deter herbivores but also deter pollinators and consequently reduce individual plant reproduction. Using empirically vetted mathematical representations of these interactions, I show that while this defense strategy has significant costs to individual reproduction it has stabilizing effects on the population and community level. Chapter six focuses on an often overlooked pollinator, predatory syrphid flies. These flies are pollinators when adults but predators of insect herbivores when in their larval stage. While this can be beneficial, I demonstrate how this dynamic can lead to a negative feedback loop in communities isolated from background biodiversity. Chapter seven expands the consideration of ecologically distinct developmental stages to plants. Incorporating independent stages of plant development into a model framework is shown to fundamentally alter the effects certain demographic rates on both population and community dynamics. This work presents novel findings regarding pollinator interactions with their environment in both anthropogenic and natural settings, contributing to foundational ecological information which will hopefully aid in managing and conserving pollinator biodiversity.PHDEcology and Evolutionary BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145954/1/prglaum_1.pd

Interpreting random forest analysis of ecological models to move from prediction to explanation

As modeling tools and approaches become more advanced, ecological models are becoming more complex. Traditional sensitivity analyses can struggle to identify the nonlinearities and interactions emergent from such complexity, especially across broad swaths of parameter space. This limits understanding of the ecological mechanisms underlying model behavior. Machine learning approaches are a potential answer to this issue, given their predictive ability when applied to complex large datasets. While perceptions that machine learning is a "black box" linger, we seek to illuminate its interpretive potential in ecological modeling. To do so, we detail our process of applying random forests to complex model dynamics to produce both high predictive accuracy and elucidate the ecological mechanisms driving our predictions. Specifically, we employ an empirically rooted ontogenetically stage-structured consumer-resource simulation model. Using simulation parameters as feature inputs and simulation output as dependent variables in our random forests, we extended feature analyses into a simple graphical analysis from which we reduced model behavior to three core ecological mechanisms. These ecological mechanisms reveal the complex interactions between internal plant demography and trophic allocation driving community dynamics while preserving the predictive accuracy achieved by our random forests

Vanadium 3d charge and orbital states in V2OPO4 probed by x-ray absorption spectroscopy

V 3d charge and orbital states in V2OPO4 have been investigated by means of x-ray absorption spectroscopy (XAS). The electronic structure of V2OPO4 is very unique in that the charge transfer between V2+ and V3+ in face-sharing VO6 chains provides negative thermal expansion as reported by E. Pachoud et al. [J. Am. Chem. Soc. 140, 636 (2018)]. The near-edge region of O is XAS exhibits the three features which can be assigned to transitions to O 2p mixed into the unoccupied V 3d t(2g) and e(g) orbitals of V2+ and V3+. The V 2p XAS line shape can be reproduced by multiplet calculations for a mixed-valence state with V2+ and V3+. The polarization dependence of the O 1s and V 2p XAS spectra indicates V 3d orbital order in which xy and yz (or zx) orbitals are occupied at the V3+ site in the face-sharing chains. The occupied xy orbital is essential for the antiferromagnetic coupling between the V2+ and V3+ sites along the chains, while the occupied yz (or zx) orbital provides the antiferromagnetic coupling between the V2+ and V3+ sites between the chains

Impervious Surface Data from Big city <i>Bombus</i>: using natural history and land-use history to find significant environmental drivers in bumble-bee declines in urban development

Site level data of the proportional coverage of impervious surface around each site used in analysi

General Supplementary Information from Big city <i>Bombus</i>: using natural history and land-use history to find significant environmental drivers in bumble-bee declines in urban development

Supporting detail on data collection and statistical analysi

Bumble bee collections data from Big city <i>Bombus</i>: using natural history and land-use history to find significant environmental drivers in bumble-bee declines in urban development

Detailed collections data of bumble bee samples used in analysi