Life Sciences Commons^™

Assessing Threats To Plant Populations: Linking Pollinator Differences To Patterns Of Plant Fitness And Population Genetics, Rieka Yu

Dissertations

Land use change is a major driver of biodiversity loss and consequently has led to the loss of genetic diversity in many plant populations due to declines in population sizes and an increase in spatial isolation. However, not all plant populations respond similarly to land-use change, suggesting there are additional mechanisms mediating plant population genetic patterns. Here, I examine the role of pollinators as this mediating factor. In Chapter 1 I conducted a meta-analysis to investigate how different types of pollinators drive changes in gene flow for plant populations in disturbed habitats, finding that different types of pollinators mediate different …

Genetic And Environmental Drivers Of Microbial Colonization In Wild Birds, Sage Rohrer

Dissertations

Wild birds are teeming with microorganisms, ranging from commensal bacteria to eukaryotic parasites. These microbes impact host health in diverse ways; some long-term residents may aid digestion or provide immune system training, while others at times may induce disease. However, the factors driving the varying colonization patterns seen across taxa are still not fully understood, and wild avian populations are particularly understudied when compared to mammalian or domesticated systems. This work examines the relative importance of genetic and environmental factors driving microbiome composition and function in wild birds. We collected fecal and blood samples from Galapagos penguins (Spheniscus mendiculus …

The Ecology And Evolution Of Species Rarity In Oaks (Quercus Spp.), Yingtong Wu

Dissertations

Rare species are susceptible to extinction due to ecological and genetic factors. Understanding the distribution, ecology, and evolution of rare species can provide useful information for effective conservation. To investigate species rarity, this dissertation focuses on a species-rich and ecologically diverse genus, Quercus (oaks). In Chapter 1, I aimed to understand how interactions between hosts and soil microbes contribute to habitat restriction in oak species. I performed a soil inoculum experiment on two pairs of sister oak species that show habitat divergence. I found that host-specific soil microbes contribute to habitat divergence and exclusion among sister species of oaks, but …

The Effects Of Prescribed Fire On Ant-Mediated Seed Dispersal In Missouri, Eva M. Colberg

Dissertations

Many aspects of animal-mediated seed dispersal are vulnerable to disturbance, including partner identity and dispersal quantity and quality. This dissertation explores ant-mediated seed dispersal of the herb Sanguinaria canadensis in Missouri Ozark oak forests, where prescribed fire is a common land management tool. In Chapter 1, I test the definition of a keystone seed disperser using absolute and relative contributions of different ant species to the quantity and distance of seed dispersal, based on field observations of S. canadensis seed dispersal. I demonstrate that the ant Aphaenogaster rudis is better described as a numerically dominant rather than keystone seed disperser, …

Effects Of Forest Restoration On The Recovery Of Dead Wood, Associated Arthropods, And Insect-Mediated Wood Decomposition, Estefania Fernandez Barrancos

Dissertations

Dead wood represents 8% of terrestrial carbon stocks and is an important source of habitat and food for decomposer and non-decomposer arthropods. However, anthropogenic disturbance reduces the amount of dead wood, putting at risk the presence of a habitat that is essential for many arthropods and other organisms that rely on it for food and shelter. Forest restoration aims to assist the recovery of ecosystems that have been damaged or destroyed and could be a means to recover both dead wood and its associated arthropod communities. This doctoral dissertation lies at the intersection of climate change, biodiversity loss and ecological …

Cognitive Ecology Of Color Vision In Orchid Bees, Andreia Queiroz Santos A Figueiredo

Dissertations

Animals interact with their environment and acquire information from it. Information can be processed by their sensory systems and influence behavior, often mediated through mechanisms of decision-making and learning. Animal pollinators acquire information from flowers and use this information to make decisions about the flowers they visit. My research aimed to understand the role of color vision in a tropical pollinator, the orchid bee Euglossa dilemma. Chapter 1 is a review exploring pollination through the lens of prepared learning. Prepared learning proposes that animals learn some associations better than others due to an evolved match with the environment. I …

The Role Of Plasticity In Bumble Bee Responses To Environmental Variability, Matthew Austin

Dissertations

An aim of contemporary biology is elucidating the causes and consequences of phenotypic plasticity. Here, I approach this aim by exploring the eco-evolutionary dynamics of phenotypic plasticity and environmental variability in bumble bees (Apidae: Bombus), a congeneric clade of eusocial pollinating insects. Throughout their evolution, bumble bees have encountered spatiotemporal variability imposed by dynamic floral environments. Today, bumble bees additionally encounter spatiotemporal variability imposed by anthropogenic environmental change. In this dissertation, I explore how phenotypic plasticity affects how successfully bumble bees respond to environmental variability imposed by anthropogenic global change (Chapters 1 and 2) and their floral resources (Chapters …

Investigating Drivers Of Genetic Structure In Plants: Global, Regional And Local Scales, Diana Gamba-Moreno

Dissertations

Genetic structure within and among plant populations is a critical component of plant biodiversity, informing local adaptation, conservation, and incipient speciation. However, its drivers remain poorly understood, especially across different spatial scales. In my dissertation I examined factors that affect plant population genetic structure at global, regional, and local scales. At the global scale, I performed a literature review of population genetic differentiation (F_ST) in seed plants based on a 337-species dataset with data on F_ST and species traits. Using phylogenetic multiple regressions, I found that F_ST is higher for tropical, mixed-mating, non-woody species pollinated by …

Vines In The Neotropics: Phylogenomics, Biogeography And Systematics In Passion Flowers (Passiflora Subgenus Decaloba Section Decaloba), Serena Acha

Dissertations

With 600 species, Passiflora is a large, morphologically complex and broadly distributed genus in Passifloraceae that represents a major challenge to scientists interested in understanding the evolutionary history of tropical vines. Passiflora has been divided into subgenera, super sections and sections. One of the most enigmatic and species-rich (~120 spp.) groups in Passiflora is section Decaloba, which occurs in the Neotropics and is particularly diverse in Andean montane forests. In this study, we used phylogenomic and population genomic approaches to investigate the evolutionary history, biologeography, species boundaries, and taxonomy of Passiflora section Decaloba. We sampled herbarium specimens, extracted …

Regional And Historical Influences On The Spatial Distribution Of Neotropical Trees, Maria Isabel Loza

Dissertations

At small spatial scales, the composition of species assemblages depends on local conditions and the dispersal of propagules from surrounding regions. In turn, processes taking place at broad temporal and spatial scales, including changes in regional physiography and climate, shape the species pools in these source regions. This dissertation seeks to understand the effects of regional and historical processes on the spatial distribution of Neotropical tree species. In chapter 1, I investigate regional enrichment of local species assemblages testing two hypothesis: i) local species assemblages are enriched by unfiltered species pools, which are composed of all species that can …

Phylogeographic Relationships Of Coereba Flaveola And Their Malaria Parasites, Meghann Humphries

Dissertations

This dissertation is broadly focused on elucidating how the geographic structure and demographic changes in host and parasite populations relate to one another, and how such interactions contribute to the generation and maintenance of biological diversity.

I begin by investigating the population structure of the Coereba flaveola (bananaquit) population within Puerto Rico, which is the apparent source of several expansions of the species into the Lesser Antilles. These findings indicate that both island and taxon effects influence the observed demographic changes. Because susceptibility to antagonists is related to both host species-specific characteristics and to geographical location, coevolutionary outcomes of these …

The Ecology Of Nest Cavity Use By Arboreal Ants In The Brazilian Cerrado: Resource Availability, Nest Modification, And Trophic Interactions, Galen Priest

Dissertations

Arboreal ants in the Brazilian Cerrado rely on cavities in living trees as nest sites. These cavities are created by a community of, wood-boring beetles, which act as ecosystem engineers. Despite the importance of these cavities as a resource, little is known about their natural abundance and heterogeneity, how ants use and modify them as nest sites, and how this interaction between cavities and their ant occupants influences trophic interactions on cerrado trees. Here I use natural history observations and manipulative experiments to address these questions. In the first chapter I quantified the occurrence, heterogeneity, and use of beetle-created cavities …

The Ecology And Feeding Behavior Of Mosquitoes In The Galapagos Islands, Samoa S. Asigau

Dissertations

Mosquitoes remain important vectors in transmitting wildlife diseases. This dissertation aims to understand the role that mosquitoes play in transmitting wildlife diseases such as avian malaria, a protozoan parasite belonging to the genus Plasmodium. Using data from wild-caught mosquitoes captured in multiple years and across multiple islands on the Galapagos Archipelago, we describe distributional patterns of mosquitoes, their range limits and assess whether there exists a disease-free refuge as occurs in Hawaii. We show that altitudinal ranges for disease transmission of avian malaria may not be bounded by a stable disease-free refuge, since mosquitoes are found at all elevations, …

Haemosporidian Parasites And Host Immune Function Of Galapagos Avifauna, Maricruz Jaramillo

Dissertations

The large number of emergent infectious diseases witnessed in the past few decades has increased interest in the ecology and distribution of potentially threatening pathogens worldwide. Island species are often considered more vulnerable to parasites due to their impoverished parasite communities, long isolation from disease and low genetic diversity. Avian surveys done by our group on the Galapagos Islands have found various pathogens infecting their endemic avifauna, including haemosporidian parasites of the genera Plasmodium and Haemoproteus. My research seeks to understand the relationships between two haemosporidian parasites (blood parasites) and their multiple bird hosts in Galapagos and to explore …

The Diversity, Costs, And Benefits Of Shelters Built By Lepidopteran Caterpillars In A Costa Rican Dry Forest, Christina Baer

Dissertations

Thousands of Lepidoptera species build shelters as caterpillars using plant material and their own silk. Although these caterpillars and their shelters are recognized as playing important ecological roles, the structural diversity of shelters and the costs and benefits of different shelters to their builders are still poorly understood. In this dissertation, I use natural history observations, observational and manipulative field projects, and molecular and phylogenetic tools to investigate these questions for a diverse and abundant shelter-building caterpillar community within the dry forest of Palo Verde National Park, Costa Rica. In Chapter 1, I develop a system for categorizing and describing …

Parasitism Of Free-Ranging Neotropical Primates: Examining Parasite-Host And Parasite-Parasite Relationships, Gideon A. Erkenswick

Dissertations

Parasites are infectious agents that require resources from host organisms to complete all or part of their lifecycles. It is customary for wild animals to acquire and maintain multiple parasitic infections during their lifetime. The effects of parasites on hosts vary across demographic and environmental variables, and in relation to each other. Moreover, the propensity for a host animal to acquire an infection can be influenced by other host species in the area that are susceptible to the same parasites. This dissertation describes and explores the natural parasite assemblage of a free-ranging community of nonhuman primates in the Peruvian Amazon …