This dissertation investigates variability in the echolocation calls of Brazilian free-tailed bats, Tadarida brasiliensis (Chiroptera: Molossidae), and explores how bats adjust echolocation call structure in response to different behavioral and ecological conditions. Substantial geographic variation exists in the echolocation call structure of T. brasiliensis throughout the species range in the US, but this variation does not correlate with geographic or climatic patterns. Most variation in call structure is due to differences between and within the calls of individuals. When exposed to broadcasts of high frequency insect sounds, free-flying bats consistently responded by shifting call frequencies away from the broadcast frequencies. This response suggests that bats are sensitive to local acoustic interference that decreases the efficiency of echo reception. In another investigation of reactions to interfering sounds, bats responded to echolocation playbacks by rapidly shifting their call frequencies away from playback frequencies, indicating that a jamming avoidance response was occurring. Bats more frequently shifted their calls upwards to higher frequencies, which may be due to maximal jamming power of the lower frequency portion of echolocation calls. Flexibility in their echolocation calls also was evident in calls produced by T. brasiliensis while emerging from roosts in a tight column formation. Bats emitted two distinct call types during emergence, sweep and hook calls, which were substantially different from foraging calls. Call structure differed between roosts, which may be related to differences in the spacing of bats within emergence columns. In a final experiment, it was found that bat activity was substantially greater in response to echolocation playbacks that contained feeding buzz calls compared to broadcasts that did not contain these signals, indicating that bats eavesdrop on the echolocation calls of conspecifics. Overall, this study documents the highly flexible nature of echolocation in Brazilian free-tailed bats and demonstrates that bats respond acoustically to behavioral and ecological influences.

Ecologists have long recognized that patterns measured in nature often depend upon the context in which they are observed and the scale at which they are observed. When studying plant populations, the role of scale and contingency becomes crucial. Thinking about a plant community as a system is essential as populations of plants are centered within a network that influences their dynamics in direct and indirect ways. Plant populations are inherently scale-dependent because they have properties as a group that can be independent of their properties as individual stems. Although the challenge of interpreting population patterns in the face of contingency and scale has been addressed conceptually, there has been less success in applying those concepts to observational and experimental studies. This dissertation addresses the challenges of modeling the demographic dynamics of a forest understory herb, Eurybia chlorolepis (Asteraceae) or mountain aster. The study population consisted of twenty patches containing between 20 and 70 individual stems in each patch. These patches spanned three sites within the Indian Camp Creek watershed in the Cosby Ranger district of Great Smoky Mountains National Park. Plants in the forest understory in this dense old-growth forest are influenced by a myriad of biotic and abiotic components of the community: light, soil characteristics, other plant species, herbivores, pollinators, seed predators, and the feet of bears. This dissertation shows that the mechanisms that influence sexual reproduction of this plant are structured almost entirely on the stem-to-stem scale, indicating little coarse-scale influence of the environment over sexual reproduction. The use of a Bayesian learning network showed that the environmental influences (soil in particular) operated most importantly in the transition from juvenile stage to adult stage. Taken together, these analyses indicate that the coarse-environtment (such as gaps, soil profiles, soil moisture, and the presence of other plants) dictates where E. chlorolepis becomes reproductive, while the success of that reproduction is dictated by mechanisms operating between individual stems.

With data from the NCEDL Multi-State Pre-Kindergarten Study, the relationship between the characteristics of program, classroom, and teachers and classroom quality was examined in this study. Classroom quality was measured by the Classroom Assessment Scoring System and the Emerging Academics Snapshot. The sample consisted of 227 pre-k teachers in state-funded programs from six states. The percentage of children from low-income families in the classroom and the number of children with limited English proficiency (the only two predictive variables that described children’s characteristics) were found to be statistically significant predictors of classroom process quality. These findings were discussed with regard to the need for more in-depth thinking about research on the relationship of structural quality and process quality in early childhood classrooms. The Snapshot was eliminated from the analyses because of low means and limited variances. In contrast to some literature, teacher qualification variables were not statistically significant predictors in this study. This was discussed with regard to the need for consistent definitions and measures of teacher qualifications and teacher training.

Invasive species are one of the greatest threats to global biodiversity. Therefore, to conserve biodiversity and manage exotic species effectively, it is crucial to determine the factors that regulate biological invasions. Historically, the study of invasions has focused on the dynamics and characteristics of successful invasive species. While studying successful invaders has enhanced our understanding of biological invasions, studying the failures can also illuminate the factors that limit invasions. To further understand the factors limiting the spread of exotic species, I studied invasion dynamics of several species in the family Pinaceae on Isla Victoria, Argentina. Approximately 80 years ago, thousands of trees of at least 135 non-native tree species were planted on Isla Victoria, many of them in the Pinaceae, but few species have escaped the plantation. I tested whether herbivory by exotic deer, seed predation or mycorrhizal facilitation might limit the spread of pine species from plantations. To test whether preferential herbivory by deer on non-native species plays a role, I conducted a cafeteria experiment. Deer browsed more intensively on native species than on exotics, suggesting that deer could potentially facilitate invasion by exotic Pinaceae. To test if seed predation limits exotic conifer establishment, I studied seed predation using field experiments. Seeds of exotics were preferred over seeds of native species, and predation was more intense in areas far from plantations than near plantations, reducing the chances of exotic seed establishment. To test the role of ectomycorrhizal symbiosis on invasion I conducted a series of experiments, in which I found that the lack of proper ectomycorrhizal fungi could limit invasion. Seedling establishment and growth rates were higher near inoculum sources (plantations) than far from such sources. Ectomycorrhizal colonization rates where higher near plantations than far from them, showing that mycorrhizal interactions could be important for understanding plant invasion. Together these studies suggest that pine invasion in Isla Victoria can be controlled by a suite of, to date, underappreciated factors.

Gratiola (Plantaginaceae tribe Gratioleae) is a genus of ca. 33 wetland-adapted herbaceous species found mostly in temperate or tropical-montane regions of the Americas, Eurasia, and Australasia. The only worldwide taxonomic treatment of Gratiola was published more than 160 years ago and only a few representatives of the genus have been included in published molecular phylogenetic studies. The overall aim of this investigation was to provide a modern systematic study of Gratiola by determining the phylogenetic placement of Gratiola within the Gratioleae using chloroplast DNA sequence data (Chapter 2); examining the phylogenetic relationships, morphological character evolution, and biogeographical patterns within Gratiola using a combination of chloroplast DNA sequence data and morphology (Chapter 3); and conducting a taxonomic study of the Gratiola neglecta species complex, a group of four closely related and predominantly eastern North American species (Chapter 4). This dissertation is the accumulation of information from three original research papers. The first paper (Chapter 2) has been accepted for publication in Systematic Botany. The second paper (Chapter 3) will be submitted to Systematic Botany. The third paper (Chapter 4) has been published in the Journal of the Botanical Research Institute of Texas. The results from this study show (1) that Gratiola sensu lato (including Amphianthus, Fonkia, Sophronanthe, and Tragiola) is monophyletic and firmly embedded in a monophyletic Gratioleae and is sister to the Old World genera Hydrotriche and Limnophila; (2) that the 33 species (including four undescribed taxa) of Gratiola group into four major clades (Diandrae, Gratiola, Nibora, Sophronanthe) that are each morphologically cohesive and largely correspond to major biogeographic regions; and (3) that the Gratiola neglecta Complex includes four species (G. neglecta, G. floridana, G. graniticola, and G. quartermaniae), two of which constitute previously undescribed species that are morphologically and ecologically distinct.

Species distribution models are increasingly being applied to questions in ecology, biogeography and evolution, and in particular to the problem of predicting the potential spread of invasive species and the potential impacts of climatic change on biodiversity. However, despite their broad application, several conceptual limitations still preclude the use of species distribution models in many theoretical and practical applications. Chief among these is the assumption that climate alone determines the geographic ranges of species, as opposed to biotic interactions and dispersal limitations, and that such species-climate relationships remain largely unchanged across space and time. In this context, I explore the degree to which climate constrains the distributions of species and how such relationships change during biological invasions and under climate change. I first examine whether species-climate relationships are conserved during the invasion of the red imported fire ant (Solenopsis invicta) and find evidence, in contrast to model assumptions, that invasive species can undergo rapid niche shifts during invasive spread and that this result is robust to variable selection. Next, I explore the degree to which migration constraints may limit the ability of Banksia (Proteaceae) species endemic to southwestern Australia to respond to climate change. I find that migration constraints may not represent a major factor in determining future patterns of biodiversity in this region as ranges of most species were projected to collapse rather than shift and that this result was consistent across different scenarios of future climate. Finally, I investigate the relative importance of dispersal limitation (as implied by seed dispersal mode) and contemporary climate in determining of patterns of biodiversity for 2543 species of plants in southwestern Australia. In contrast to the predicted relationship, I find that the distributions of dispersal-limited species were less constrained by dispersal and more constrained by climate than the distributions of ostensibly more vagile species. Taken together, these studies suggest, in strong contrast with model assumptions, that species climate-relationships can change, sometimes rapidly, under environmental change such that future patterns of biodiversity and biological invasions may not be readily predictable from current distributions of species.

Microbial biodegradation of polycyclic aromatic hydrocarbons (PAHs) is the primary means of attenuation of these toxic and carcinogenic compounds from contaminated soils and sediments. The documented toxicity and carcinogenicity of many PAHs demands remedial action for PAH-contaminated soils and sediments. This is especially important for historically contaminated sites, where higher molecular weight PAHs (HMW) are recalcitrant. Recently, fast-growing Mycobacteria have been identified that can degrade HMW PAHs, such as pyrene and benzo[a]pyrene. These bacteria have been isolated from a variety of geographical locations, indicating a cosmopolitan distribution. This dissertation work was driven by the need for a better understanding of the ecology, distribution, and dynamics of indigenous microbial populations that can biodegrade PAHs, with an emphasis on Mycobacteria. Both culture-independent molecular approaches and cultivation were used to 1) determine the presence of pyrene-degrading Mycobacterium genotypes and compare dynamics to proteobacterial naphthalene-degradation genotypes; 2) determine the distribution of these genotypes across environments, including different geographical locations (Chattanooga Creek and Lake Erie) and different physical environments (sediments vs. suspended particles); and 3) provide a link between functional pyrene genotypes and phylogenetic identity of isolated pyrene-degrading organisms. The results of these studies indicate the pyrene-degrading Mycobacteria have broad, cosmopolitan distribution in contaminated sediments and suspended particles. Isolation of pyrene-degrading organisms from both Chattanooga Creek and Lake Erie has provided strong evidence for horizontal transfer of pyrenedegrading genes between diverse genera. This work demonstrates the prevalence of pyrene-degrading organisms in contaminated sediments and implicates an integral role in natural attenuation of HMW PAHs.

Since its introduction to Florida, the brown anole, Anolis sagrei, has steadily expanded its range into that of its native congener in the southeastern United States, the green anole, A. carolinensis. Anolis sagrei achieves very high densities both in its native and invaded range and appears to impose population declines and shifts in the realized habitat niche of A. carolinensis. In order to investigate whether these effects arise prior to the adult age class in which they have previously been described, I studied the behavior of juvenile anoles at the individual, dyadic, and neighborhood levels. Contrary to some characterizations of adult microhabitat selection, distribution models of individual movement on laboratory thermal gradients indicate that juvenile A. carolinensis are likely to occupy warmer sites than A. sagrei, but with broad overlap in the full range of temperatures selected by these species. Staged dyadic encounters between socially naïve juveniles of these species, however, suggest that intrinsic individual characteristics influencing dominance and behavioral exclusion in the youngest juvenile anoles favor A. carolinensis over A. sagrei. To confirm these observations and explore their consequences under conditions representative of natural juvenile assemblages, I compared the behavior and habitat use of A. carolinensis juveniles in single-species field enclosures with A. carolinensis and A. sagrei juveniles in two-species enclosures and described changes in the partitioning of space over the first weeks of life. Within the first week, thermal microhabitat partitioning was apparent and juvenile A. carolinensis in the presence of A. sagrei juveniles exhibited an upward shift in mean perch height similar to that seen in reproductive males following experimental imposition of sympatry in adults of these species. Despite the shift in structural habitat use of A. carolinensis juveniles in the presence of A. sagrei, there was no observed consequence of syntopy on growth rate or survival. This study suggests no immediate role of juvenile interactions on numerical declines in A. carolinensis in sympatry with A. sagrei, but does indicate that a more ontogenetically comprehensive approach is warranted in the characterization of niche differences and habitat partitioning.

Increased forest growth in response to rising atmospheric concentrations of CO2 may mitigate a portion of fossil fuel emissions, especially if carbon is sequestered in longlived biomass or soil pools. Greater carbon uptake under elevated atmospheric [CO2] in forested ecosystems may facilitate the production of small diameter (i.e. “fine”) roots used for nutrient acquisition. Increased fine-root production in forested ecosystems may affect soil carbon storage and nitrogen cycling because fine roots live and die in the span of a year. My dissertation research took advantage of a long-term, on-going Free-Air CO2-Enrichment experiment in a sweetgum (Liquidambar styraciflua L.) forest stand at Oak Ridge National Laboratory to investigate the causes and consequences of increased fine-root production under elevated [CO2]. To examine the premise that N limitation was the cause of increased fine-root production in the CO2-enriched sweetgum stand, I fertilized plots in an adjacent sweetgum plantation with 200 kg ha-1 of N as urea. The relative C flux to wood production that I observed in the fertilized treatment is consistent with the premise that increased root production in the adjacent FACE experiment is in response to N limitation. To examine the consequencesof increased fine-root production under elevated [CO2], I: (1) quantified fine-root biomass and N inputs at several soil depths using a long-term minirhizotron data set combined with continuous, root-specific measurements of root mass per unit length and [N], and (2) allowed fine roots grown under current and elevated [CO2] to decompose in a common garden experiment by modifying existing litterbag methodology. I found that C and N inputs via root mortality were doubled under elevated [CO2], and half of the inputs were below 30 cm soil depth. However, CO2-enrichment had no effect on fine-root chemistry or decomposition rate, and therefore more root detritus may be incorporated into long-lived soil organic matter under elevated [CO2]. Quantification of the effects of elevated CO2 on the fate of a greater quantity of fine-root detritus, especially at depth in the soil, will provide critical information needed for predicting processes such as long-term soil C storage and N cycling in response to environmental change.

Phenotypic correlations between traits are thought to reflect genetic correlations. However, traits related to a central function, like reproduction, need not all be genetically correlated. Identifying genetic correlations between behavioral traits can help identify the evolutionary relationship between different behaviors, as well as provide initial information on the number of genes involved in behavioral variation and the rates and direction of evolution. This body of work describes the phenotypic and genetic relationship between mating traits in the parasitoid wasp genus Nasonia. Chapters 2 and 3 describe behavioral differences among the three species of Nasonia. Two of the species, N. vitripennis and N. giraulti, show extreme differences for several behavioral traits. Nasonia vitripennis females mate almost exclusively after emergence from the host puparium and show a strong propensity to remate, and males of this species show strong site fidelity after emergence. Conversely, N. giraulti females mate almost exclusively inside the host (called within-host mating; WHM), show a low frequency of remating, and males show no site fidelity and disperse after emergence. The third species, N. longicornis, is similar to N. vitripennis for male site fidelity, but shows between line variation for WHM and female remating. I used the between line variation to create divergent recombinant inbred lines (RILs), 24 of which were screened for ten different behavioral traits (Chapter 4), including WHM, male site fidelity, remating, components of male courtship, and male and female developmental traits. Three behaviors were genetically correlated; WHM was positively correltated with remating frequency and remating frequency was negatively correlated with male courtship duration. The relationship between WHM and remating frequency could not be explained in terms of timing of female receptivity. However, remating frequency was directly correlated with when females became sexually receptive as early female receptivity was found in lines with high remating frequencies. I also address the evolution of these behaviors in an ecological context (Chapter 5). WHM is thought to have evolved as a byproduct of selection against hybridization in nature, and the ecological distribution of Nasonia,a both within nests and host pupae, is consistent with this hypothesis.