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

Synthetic Symbiosis under Environmental Disturbances

By virtue of complex ecologies, the behavior of mutualisms is challenging to study and nearly impossible to predict. However, laboratory engineered mutualistic systems facilitate a better understanding of their bare essentials. On the basis of an abstract theoretical model and a modifiable experimental yeast system, we explore the environmental limits of self-organized cooperation based on the production and use of specific metabolites. We develop and test the assumptions and stability of the theoretical model by leveraging the simplicity of an artificial yeast system as a simple model of mutualism. We examine how one-off, recurring, and permanent changes to an ecological niche affect a cooperative interaction and change the population composition of an engineered mutualistic system. Moreover, we explore how the cellular burden of cooperating influences the stability of mutualism and how environmental changes shape this stability. Our results highlight the fragility of mutualisms and suggest interventions, including those that rely on the use of synthetic biology.IMPORTANCE The power of synthetic biology is immense. Will it, however, be able to withstand the environmental pressures once released in the wild. As new technologies aim to do precisely the same, we use a much simpler model to test mathematically the effect of a changing environment on a synthetic biological system. We assume that the system is successful if it maintains proportions close to what we observe in the laboratory. Extreme deviations from the expected equilibrium are possible as the environment changes. Our study provides the conditions and the designer specifications which may need to be incorporated in the synthetic systems if we want such "ecoblocs" to survive in the wild

Balance manifolds in Lotka-Volterra systems

The Lotka-Volterra equations are a dynamical system in the form of an autonomous ODE. The aim of this thesis is to explore the carrying simplex for non-competitive Lotka-Volterra systems for the case of 2- and 3-species, where it is referred to as a balance simplex. Carrying simplices were developed by M.W. Hirsch in a series of papers. They are hypersurfaces which asymptotically attract all non-zero solutions in the phase portrait. This essentially means that all the non-trivial dynamics occur on the carrying simplex, which is one dimension less than the system itself. Many of its properties have been studied by various authors, for example: E.C. Zeeman, M.L. Zeeman, S. Baigent, J. Mierczyński. The first few chapters of this thesis explores the 2-species scaled Lotka-Volterra system, where all intrinsic growth rates and intraspecific interaction rates are set to the value 1. This simplification of the model allows for an explicit, analytic form of the balance simplex to be found. This is done by transforming the system to polar co-ordinates and explicitly integrating the new system. The balance simplex for this 2-species model is precisely composed of the heteroclinic orbits connecting non-zero steady states, along with these states themselves. The later chapters of this thesis focuses on the 3-species case. The existence of the balance simplex in particular parameter cases is proven and it is shown to be piecewise analytic (when the interaction matrix containing the parameters is strictly copositive). These chapters also work towards plotting the balance simplex so it can be visualised for the 3-species system. In another chapter, more general planar Kolmogorov models are considered. Conditions sufficient for the balance simplex to exist are given, and it is again composed of heteroclinic orbits between non-zero steady states

Reticulate Evolution: Symbiogenesis, Lateral Gene Transfer, Hybridization and Infectious heredity

info:eu-repo/semantics/publishedVersio

Structured Equations for Complex Living Systems - Modeling, Asymptotics and Numerics

Complex living systems differ from those systems whose evolution is well described by the laws of Classical Physics. In fact, they are endowed with self-organizing abilities that result from the interactions among their constituent individuals, which behave according to specific functions, strategies or traits. These functions/strategies/traits can evolve over time, as a result of adaptation to the surrounding environment, and are usually heterogeneously distributed over the individuals, so that the global features expressed by the system as a whole cannot be reduced to the superposition of the single functions/strategies/traits. Quoting Aristotle, we can say that, within these systems, "the whole is more than the sum of its parts". As a result, when we study the dynamics of complex living systems, there are new concepts that come into play, such as adaptation, herding and learning, which do not belong to the traditional vocabulary of physical sciences and make the dynamics of these systems hardly to be forecast. Moving from the above considerations, the subject of my PhD was the development and the study of structured equations for population dynamics (partial differential equations and integro-differential equations) applied to modelling the evolution of complex living systems. In particular, I designed models for multicellular systems, living species and socio-economic systems with the aim of inspecting mechanisms underlying the emergence of collective behaviors and self-organization. In the framework of structured equations, individuals belonging to a given system are divided into different populations and heterogeneously distributed characteristics are modelled by suitable independent variables, the so-called structuring variables. For each population, a function describing the distribution of the individuals over the structuring variables is introduced, which evolves through a partial differential equation, or an integro-differential equation, whose parameter functions are defined according to the phenomena under study. I decided to use such mathematical framework since it makes possible to effectively model the afore mentioned complexity aspects of living systems and provides an efficient way to reduce complexity in view of the mathematical formalization. With particular reference to multicellular systems, I focused on the design and the study of mathematical models describing the evolutionary dynamics of cancer cell populations under the selective pressures exerted by therapeutic agents and the immune system. Proliferation, mutation and competition phenomena are included in these models, which rely on the idea that the process leading to the emergence of resistance to anti-cancer therapies and immune action can be considered, at least in principles, as a Darwinian micro-evolution. It is worth noting that most of these models stem from direct collaborations with biologists and clinicians. Besides local and global existence results for the mathematical problems linked to the models, my PhD thesis presents results related to concentration phenomena arising in phenotype-structured equations and opinion-structured equations (i.e., the weak convergence of the solutions to sums of Dirac masses), and with the derivation of macroscopic models from space-velocity structured equations. From the applicative standpoint such concentration phenomena provide a possible mathematical formalization of the selection principle in evolutionary biology and the emergence of opinions; macroscopic models, instead, offer an overall view of the systems at hand. Numerical simulations are performed with the aim of illustrating, and extending, analytical results and verifying the consistency of the model with empirical dat

Quantitative Ecology: A New Unified Approach

This ebook is available for download as a PDF.Quantitative Ecology introduces and discusses the principles of ecology from populations to ecosystems including human populations, disease, exotic organisms, habitat fragmentation, biodiversity and global dynamics. The book also reformulates and unifies ecological equations making them more accessible to the reader and easier to teach

European grapevine moth, Lobesia botrana Part I: biology and ecology

Though the European grapevine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) can feed on more than forty plant species, grapevine is the preferred crop worldwide. This moth is a western palearctic species that has recently spread to Chile, Argentina, and California. The possible further expansion in other regions of the Americas is greatly feared and should be monitored carefully in the near future. In this framework, we provide an updated review of the current knowledge on its taxonomy, morphology, biology, ecology, genomics, geographic distribution, and invasiveness. Then, in the last section, we develop a research agenda pointing out significant challenges for future investigations on bio-ecology and invasion biology, which are tightly connected with the prevention and management strategie

Effects of sex and competition on evolutionary survival of Chlamydomonas reinhardtii populations in deteriorating environments

Ongoing global change has made understanding the factors that affect adaptation and survival of populations in the context of changing environments a central problem in evolutionary biology. Special focus has been given to the probability of survival through genetic adaptation to lethal environments; a process termed evolutionary rescue. Many studies of this process, both theoretical and empirical, have been carried out over the last two decades. As a result, we now understand how a number of factors may affect the probability of population survival. However, two factors that are known to affect evolutionary responses, mode of reproduction and interspecific interaction, have received limited attention. The main aim of my work was to investigate whether and how mode of reproduction and negative interspecies interactions (competition) affect the probability of evolutionary rescue. To achieve this goal, I set up a series of selection experiments, by propagating populations of unicellular alga Chlamydomonas reinhardtii in various stressful conditions, and monitored their survival and fitness. To investigate the effect of sex in these experiments, I manipulated mode of reproduction, by constructing the experimental populations allowed to reproduce either only sexually or asexually or both. To investigate the effect of competition, I manipulated the presence of the competitor(s) in the experimental populations, by cultivating them either in presence or absence of the competitor. I first tested the effect of rate of environmental deterioration and mode of reproduction on extinction dynamics and evolutionary rescue of the experimental populations. I found positive correlation between the rate of extinctions and the rate of environmental deterioration. The experiment revealed an interaction between mode of reproduction and the rate of deterioration, manifested through significantly reduced extinction rate of sexual populations relative to asexual populations in environment deteriorating at intermediate rate. I then investigated the effect of sex and competition on the probability of evolutionary rescue, by propagating the experimental populations in environment deteriorating in a simple way (the change comprising a single abiotic factor) and complex way (the change of both abiotic and biotic factors). I found the negative effect of competition on the probability of evolutionary rescue, and beneficial effect of sex in both types of environmental deterioration, reflected in higher number of rescued populations relative to asexual group. I then tested whether phylogenetic relatedness between a competitor and the focal species and the extent of their ecological similarity affect the likelihood of evolutionary rescue, by subjecting the experimental populations to the presence of 10 different competitors, isolated from two different types of habitats, and each being positioned on a different branch of the phylogenetic tree of Chlamydomonas genus. The probability of evolutionary rescue was contingent on the identity of a competitor species, but the results showed no significant effects of phylogenetic relatedness and ecological similarity. Finally, I investigated which experimental factors could potentially select for the long-term maintenance of sex, by subjecting the experimental populations to different types of selective environments (directional and fluctuating change of abiotic factors, the presence of the competitor) and monitoring the frequency of sex over the course of time. No selective environment significantly increased the rate of sex in the experimental populations. In contrast, I found reduction in frequency of sex in the populations subjected to fluctuating environmental change. My results demonstrate that both mode of reproduction and competition affect the probability of evolutionary rescue, which is generally positively affected by sex and negatively affected by competition. However, these general effects may be altered by other factors, namely mode of environmental change and the identity of the competitor species