This study examined the existing, or potential, risk of invasion by street trees into an urban forested park (Breithaupt Park, a 32.5 hectare semi-forested park, and its surrounding residential neighbourhood in the City of Kitchener.). The primary research question is: What are the spatial distribution and dispersal patterns of street trees and park trees in urban areas? For street populations, height, crown spread, diameter at breast height (DBH), tree condition, trunk condition and foliage transparency were measured. Qualitative tree health indicators were used to gauge the condition of the street tree population only. For trees in Breithaupt Park, a point-quarter sampling method combined with a line-plot sampling method was used. There were 33 identified (and several unidentified) species of street trees and 24 identified species of forest trees. Acer platanoides was the most abundant street tree species, while Acer saccharum was the most abundant forest tree species. 52% of the street tree population and 9% of the forest tree population were exotic species; however, the exotics were mainly species not originating from the nearby streets (i.e. Rhamnus cathartica). Despite the well-established population of exotic invasive species such as Acer platanoides on the streets, spatial assessment of the nearby forested park revealed that relatively few exotic species had actually established there. Acer platanoides composed 1.9% of all trees, 3.2% of all saplings and 2.7% of all seedlings in the forest sample. The four possible sources of Acer platanoides seeds were trees planted on the street, trees planted in backyards, the leaf drop site in the parking lot of Breithaupt Park (only in the fall) and trees potentially planted directly in the forest. Explanations for the lack of invasion by Acer platanoides (in particular) include: 1) houses located between Acer platanoides street trees and Breithaupt Park functioning as a barrier to seed dispersal; 2) the highway traversing the northeast corner of the park; 3) the short length of time since Acer platanoides street trees reached their age of maturity to produce enough viable seeds to invade the forest and the lag time in the establishment phase; 4) unique park characteristics; and 5) opposing predominant wind directions. While Acer platanoides may be more invasive under different circumstances, it was concluded that Acer platanoides is not currently invading the park at a considerable rate but may be tending towards a future invasion. The main recommendations are: 1) to not cut down the Acer platanoides currently growing as street trees as they do not pose a high risk of invasion (though this is specific to the current study); 2) to manage the forest for invasive species and remove and restore the ecology of the forest as necessary; 3) to remove Acer platanoides currently growing in the forest; and 4) to replace dead street trees with non-invasive, hardy native trees instead of the historical planting of Acer platanoides and other exotics, in case the risk of invasion changes because of climate or urban design changes.

Conservation in Canada is increasingly driven by land use planning processes. Approaches to governing nature conservation have shifted dramatically from protecting isolated pristine areas to greater attention to the remaining fragments of greenspace in urban, semi-urban and rural areas. The ways that societies govern and use nature are always changing, and these physical management actions are connected to deeply rooted cultural norms and values about the ideal relationship between humans and nature. In the land use planning approach to conservation, citizens and governments find value and construct meaning for remaining nature rather than beginning with normative considerations of what is most worthy of protection. At the root of this conservation planning trend is a growing appreciation for hybrid nature that is valued as natural in spite of the past or present influences upon it. This represents a dramatic shift from the traditional values involved in North American nature conservation, where nature was most valued for its perceived separation from human influence and protected to maintain its untouched qualities. In light of these ideological shifts in the ways that Canadians value and in turn manage nature, is there a corresponding change in the ways that conservation activists perceive environmental value and evaluate naturalness? An increasing number of studies demonstrate that public valuation of nature is not limited to pristine environments: even highly disturbed environments can be valued as natural and are not perceived as a form of lesser nature. Conceptions of what is natural and what is not are highly subjective and variable; in particular, the body of work on the social dimensions of both invasive species and ecological restoration demonstrates the ways in which people construct naturalness in accord with their values and cultural context. By exploring the extent to which people perceive invasive species as reducing naturalness and how ecological restoration is perceived to restore it, these subjects serve as excellent conceptual lenses for exploring constructions of nature. This study explores the subtle variations in environmental values and perception of naturalness among a study population who self-identify as pursuing the same goal: ensuring the continued protection of the Oak Ridges Moraine. The Moraine is a partly urbanized landform in southern Ontario that is situated within a complex hybrid socio-ecological landscape. It is also the subject of an active and high profile conservation movement that has spanned over 40 years. Using a combination of interviews and Q Method, this study explored how citizens engaged in Oak Ridges Moraine conservation perceive both the current and ideal state of naturalness on the Moraine, with specific emphasis on how the discourses these citizens use to frame the Moraine invoke the concept of naturalness Findings from this study reveal that Moraine activists represent a conservation paradox: they value the natural, non-human qualities of the landform, yet at the same time identify the Moraine as a hybrid landscape with both social and ecological qualities. In particular, respondents indicated a strong interest in naturalness in the context of invasive species and ecological restoration, yet at the same time identified the naturalness of the Moraine to be a lesser priority in the face of urban development pressures. In this way, citizens engaged in Moraine conservation respond to the hybrid quality of the Moraine landscape by moving beyond the binary distinction between nature and society, situating themselves as both apart from and a part of the landscape at the same time. This finding demonstrates how values for conserving nature are affected by hybridity between social and ecological systems, and suggests how embracing the paradox of hybrid nature can contribute to understanding and managing complex socio-ecological systems.

<p>The truffle genus Tuber (Ascomycota, Pezizales, Tuberaceae) produces underground mushrooms widely sought as edible fungi. Tuber species are distributed throughout Northern hemisphere forests and form obligate ectomycorrhizal symbiosis with trees within the Pinaceae, Fagaceae, Betulaceae, and Juglandaceae. </p><p>The transition to a truffle form (from an epigeous form) has occurred independently, multiple times in both the Ascomycetes and Basidiomycetes. One instance has given rise to the Tuberaceae, which is composed entirely of obligate ectomycorrhizal species. Attempts to cultivate European truffle species T. melanosporum, T. aestivum, and T. borchii are underway in North America and other parts of the world and have been met with mixed success.</p><p>The overarching goal of my dissertation is to address the systematics, ecology, and biogeography of Tuber within a phylogenetic framework. Multiple loci were sequenced from Tuber ascoma collected worldwide including ectomycorrhizae, though an emphasis was placed on sampling taxon within North American. Maximum likelihood, maximum parsimony, and Bayesian inference were used for phylogenetic reconstructions. </p><p>A taxonomic and phylogenetic overview of the family Tuberaceae is presented in Chapter 1. Tuber is resolved as monophyletic. In Chapter 2, through greater taxon sampling including epigeous and hypogeous Helvellaceae outgroups and related South American taxa, a resolved multi-gene phylogeny of the Tuberaceae and putative epigeous ancestor of Tuber is presented. A previously unknown South American lineage that contains both epigeous and hypogeous taxa is resolved as sister to the Tuberaceae. Chapter 3 is focused on issues of cryptic speciation and taxonomy within the Tuber gibbosum clade. The four species resolved in the Gibbosum clade appear to be endemic to the Pacific Northwest and associated primarily with Gymnosperms. Chapter 4 is a meta-analysis of all known Tuber ITS rDNA sequences (e.g. from Genbank and generated from herbarium collections) available at the time. These were placed within the Tuber phylogeny to assess species diversity, long-distance dispersal, and host associations. In total, 120 phylotypes were detected (based on a 96% similarity criterion). Tuber shows high levels of continental endemism. I hypothesize that species shared between continents and having low ITS variability (<1%) are the result of recent human-mediated introduction events. Chapters 5 and 6 are focused on the ectomycorrhizal ecology of the economic truffle T. lyonii, which is native to Eastern and Southern North America. There is a phenomenon of Tuber lyonii fruiting in pecan orchards. Pecans (Carya illinoinensis) are in the Juglandaceae, an understudied ectomycorrhizal plant family. I sampled the ectomycorrhizal communities of pecan orchards (associated with the production of the North American truffle species Tuber lyonii). In Chapter 5 I discuss four Tuber taxa discovered in these pecan orchards, their abundance and haplotype diversity. Chapter 6 examines the ectomycorrhizal communities across the five pecan orchards sampled. I show that multiple Tuber species, including Tuber lyonii, are dominant in the ectomycorrhizal community. Chapters 7 and 8 focus on black truffles in the Melanosporum clade. In Chapter 7 I document that Tuber indicum has been introduced into North America multiple times, and through ectomycorrhizal synthesis I demonstrate that this Asian species can associate readily with angiosperm and gymnosperm hosts endemic to North American. In Chapter 8 I describe a quick and reliable method for the determination of Tuber melanosporum. The method is based on direct PCR and species-specific primers and is very useful for rapid diagnostics. I have adapted this approach for other truffle and mushroom species. </p><p>Three major findings emerge from my dissertation research: 1) Tuber is more diverse than previously realized; 2) Tuber exhibits high levels of regional and continental endemism; 3) Taxonomic issues remain in many species complexes worldwide (including the Tuber candidum complex in North America, the Tuber excavatum complex in Europe, the Tuber indicum complex in Asia). Taxonomic challenges also remain regarding species known only from ectomycorrhizal or anamorphic states. The discovery of additional Tuber species is expected as the truffle flora of undersampled regions become better studied and incorporated into the Tuberaceae phylogeny.</p> / Dissertation

The first objective of this study was to investigate the role of an invasive grass species, Arundo donax (L.), on the hydrologic cycle. At a site on the Rio Grande in South Texas, we measured the gas exchange of carbon dioxide and water vapor at the leaf scale and structural characteristics, such as leaf area and shoot density, at the stand scale. In order to assess the effect of water availability, this study was conducted along transects perpendicular to the edge of the river along a potential moisture gradient. The second objective was to quantify the effect of two herbivores, an armored scale, Rhizaspidiotus donacis (Leonardi), and a stem-galling wasp, Tetramesa romana (Walker),on the photosynthetic and transpiration rates of A. donax. Leaf gas exchange measurements were made to determine the direction and magnitude of the effect on physiological processes and by what mechanisms any effects arose. Stands of A. donax used approximately 9.1 � 1.1 mm of water per day. This rate of water use was at the high end of the spectrum for plants. The major controls on stand scale transpiration were evaporative demand, leaf area index, and water availability. During two summer seasons, stand scale transpiration varied greatly, following the pattern of variability in precipitation, suggesting that recent rainfall constituted a significant proportion of the water taken up by this species. Herbivory by a stem-galling wasp and a sap-feeding scale, both separately and together, reduced the rates of leaf scale physiological processes in A. donax. The efficacy of the wasp was density dependent, and this herbivore reduced the carboxylation rate of Rubisco. The effect of the scale took approximately five months to manifest, which coincided with generation time. Scale reduced photosynthesis by decreasing the maximum rate of electron transport. When the two insects were both present, the effect of their herbivory seemed to be additive. These results will assist the responsible management agencies in evaluating the propriety of using one or both of the insect herbivores as biological control agents.

The non-game wildlife trade poses a risk to our natural landscape, natural heritage, economy, and security. Specifically, the trade in non-game reptiles and amphibians exploits native populations, and is likely not sustainable for many species. Exotic amphibian and reptile species pose risk of invasion and directly or indirectly alter the native landscape. The extent of non-game amphibian and reptile trade is not fully understood and is poorly documented. To quantitatively describe the trade in Texas, I solicited data from the United States Fish and Wildlife Service's (USFWS) Law Enforcement Management Information System (LEMIS) and Texas Parks and Wildlife Department's (TPWD) non-game dealer permits. I surveyed amphibian and reptile pet owners, breeders, Internet sites, pet shops, and meat and seafood establishments by visits, electronic surveys, and observations. The trade in exotic species of amphibians and reptiles in the state of Texas was found to be popular in two ways; the importation of wildlife products and sale of live specimens for pets. Persisting in the pet trade were species known to be exotic, a problem made worse by lack of regulations governing the import, export, and keeping of exotic species. Trade in wild collected native species was primarily for export to foreign countries. Collection of turtles from the wild in Texas was heavy until 2008, when TPWD restricted collection to private waters. Collection of other species from the wild was minimal, with the exception of the Western Diamond-backed Rattlsnake (Crotalus atrox) for rattlesnake roundups. Native species were found to exist in the pet trade, but primarily as genetic color variants that do not occur in the wild, an indication that captive breeding may be relieving pressures on wild caught specimens. Minor changes in reporting requirements and permitting systems at the state and federal level would improve the management of exotic and native amphibians and reptiles that persist in the trade. Changes that include standardized taxonomic reporting requirements at state and federal level, streamlined permitting system for individuals wishing to collect from the wild in Texas, bag limits and seasons for wild collection, increased reporting requirements for owners of exotics, and enforcement of reporting errors would aid in management of exotic and native amphibians and reptiles in the trade.

Life history traits such as growth, survival, and clonality can vary within a population. When such variation exists in a population of an invasive species, it can affect population dynamics, and if any part of the variation has a genetic basis the population can evolve in response to control regimes. Evolutionary responses to control efforts may shift the population towards a few more resilient genotypes, or towards different types in different microenvironments, depending on the scale of gene flow with respect to the patchiness of the environment. The purpose of this study is to examine whether the application of stress similar to control efforts (light level manipulation and biomass removal) results in varying emergence, growth, and survival rates between samples taken from spatially separated patches of the invasive clonal grass Imperata cylindrica. Accelerated Failure Time (AFT) and logistic regression models were fit to survival, emergence and growth data collected from two experiments in which samples collected from four spatially separated Imperata cylindrica patches were exposed to light level manipulation and biomass removal. Patch identity plays a large role in explaining variation in time-to-emergence, time-to-death, and probabilities of emergence and survival, especially under stressed conditions. Rhizome and above ground biomass characteristics also play substantial roles in explaining variation in emergence, survival, and growth, though more so under non-stressed conditions. Our results warrant further study of heterogeneous responses to stressful conditions, especially those imposed under control and management regimes. This heterogeneity may have important impacts on population processes such as maintenance, expansion, and gene flow.

Although the process by which fertilization occurs in bryozoans is well described, the ability to self-fertilize and the subsequent ecological consequences are poorly understood. Culturing experiments were conducted examining the effects of selfing on offspring survival and reproduction in the simultaneous hermaphrodite Bugula stolonifera collected from Eel Pond, Woods Hole, MA. Results from these experiments document significant decreases in survival and fecundity of selfed offspring, compared to outcrossed controls, suggesting that these animals are not routinely self-fertilizing in Eel Pond. How these arborescent colonies minimize selfing remains unclear, but it is hypothesized that conspecific aggregations could serve to minimize the chances that a colony utilizes its own sperm for fertilization. The genetic composition of these aggregations was investigated using a newly developed microsatellite library. As larvae routinely metamorphose on conspecific colonies, the possibility that larvae select or avoid their maternal colony was also investigated. Analyses of genetic structure document homogeneity throughout these aggregations on extremely small spatial scales, suggesting high amounts of larval dispersal within aggregations. When combined with results from parentage-exclusion and kinship analyses, these results indicate that a colony's nearest neighbors are not composed of siblings, potentially minimizing inbreeding. Molecular analyses were then used to determine if the high larval dispersal within aggregations resulted in high mixing between aggregations. Sites within Eel Pond separated by 100-300 m were routinely sampled from 2009 to 2011, and analyses were conducted to investigate potential inter- and intra-annual genotypic differentiation within and between aggregations. Results document that although low levels of mixing could result in increased homogeneity between some aggregations, barriers to genetic exchange prevent mixing between most sites. Further, inter-annual comparisons within sites document that significant differentiation can occur between reproductive seasons. Hence, any potential homogeneity achieved between sites during one reproductive season will likely be lost by the beginning of the next reproductive season. Additionally, while sampling in Eel Pond in 2010, I document the first occurrence from the western Atlantic Ocean of another aggregating arborescent bryozoan, Tricellaria inopinata. The growth and reproductive biology of these animals was monitored throughout 2011; results suggest that this introduction is likely to persist.

The historically introduced House Rock Valley bison herd has, in recent years, migrated from the eastern Arizona Strip onto the Kaibab Plateau within Grand Canyon National Park. Bison are considered a nonnative species to the southern Colorado Plateau, and the animals adversely impact sensitive ecosystems prompting National Park Service wildlife managers to pursue their removal. Archaeofaunal evidence of bison in the Grand Canyon and neighboring regions, however, raises concern that bison may in fact be native. Assessing the evidence within a zooarchaeological interpretive framework is critical since mere presence/absence lists of bison remains do not address the potentially complex cultural processes involved in the formation of archaeofaunal assemblages. Inter-assemblage comparisons illustrate a decline in relative abundance and skeletal completeness correlated to distance from traditionally understood historical bison distribution. If bison were present in the Southwest, as the evidence suggests, they likely entered the region only occasionally as small, dispersed herds.

Invasive species such as quagga mussel (Dreisseina bugensis) alter native ecosystems around the world. This study uses genetic markers to examine historical lineages for quagga mussels in lakes (reservoirs) of the Colorado River System. Specimens were collected from Lake Mead, Lake Mohave, Lake Pleasant, Lake Havasu, Lower Otay Reservoir, Yuma Area, and two Central Arizona Project pumping stations. Objectives of this project were to perform analyses of genetic variability within populations and determine if relatedness among individuals could resolve whether they originate from a single, or multiple, invasion events and genetically distinguish the populations at each water body. Analyses examined the mitochondrial DNA COI region and eight microsatellite DNA markers. Three populations were characterized in the study area and compelling information gathered about gene flow between them. Results indicate that microsatellite markers are useful to track quagga mussel invasions and provide insights into migration patterns that would otherwise be missed.

Shifting patterns of precipitation associated with climate change may affect water-limited ecosystems to a greater degree than atmospheric CO2 or temperature changes, yet we lack a mechanistic understanding of the effects of water in these ecosystems. In water-limited ecosystems, annual net primary productivity correlates strongly with total annual precipitation. However, precipitation in these ecosystems arrives in episodic events, suggesting that biophysical investigations should focus on the implications of discrete precipitation events. Further, examining dynamics of ecosystem processes over a period of days or weeks promises to link our leaf-level mechanistic understandings with larger scale patterns and temporal dynamics of ecosystem photosynthetic CO2 uptake, respiration and evapotranspiration.The objectives of this dissertation were to quantify: (1) the influence of biotic and abiotic features of an ecosystem (e.g., species composition and soil physical characteristics) on short-term patterns of resilience and resistance to a precipitation pulse; (2) the role of antecedent climatic conditions and the seasonal timing of rainfall in limiting ecosystem carbon exchange in response to precipitation events; and (3) the effect of changes in woody plant abundance on seasonal ecosystem carbon dynamics in relation to the North American Monsoon.Major findings and contributions of this research include defining the concepts of ecosystem functional resistance and resilience and their implications in the presence of a dominant nonnative bunchgrass in semi-arid grasslands (Appendix A); a better understanding of the influence of warm-season precipitation variability and the seasonal timing of rainfall on ecosystem carbon dynamics in a semi-arid grassland (Appendix B); the use of flux duration analysis, a novel approach to analyzing ecosystem carbon and water flux time-series data to distinguish between "pulse-driven" or "steady-state" ecosystems (Appendix C); and, finally, the application of flux duration analysis to quantify the sensitivity of ecosystem carbon exchange in response to seasonal rainfall in a riparian grassland and shrubland and the role that plant functional type diversity may play in constraining carbon exchange sensitivity (Appendix D).