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.

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

Breast cancer is the most common cancer in Taiwanese women and the invasive ductal carcinoma (IDC) is the most common type. Increasing evidence shows that cancer stem cells (CSCs) have been implicated in tumorigenesis, tumor progression, and drug-resistance. In addition, four reprogramming factors (Octamer-binding Protein 4 (Oct4), Sex-determining Region Y (SRY)-related Box 2 (Sox2), Nanog and Lin28) employed to induce induced pluripotent stem (iPS) cells are associated with CSCs formation. The purpose of this study was to investigate the relationship of the protein expression levels of the reprogramming factors (Oct4, Sox2, Nanog and Lin28) with the tumorigenesis, clinicopathologic outcomes and prognosis of breast IDC patients. Immunohistochemistry (IHC) assay of tissue microarrays, made by 309 IDC and 20 breast fibrosis paraffin embedded samples, were used to examine the protein expression levels of Oct4, Sox2, Nanog and Lin28 in normal mammary ductal tissues, tumor adjacent normal mammary ductal tissues, ductal carcinoma in situ (DCIS), IDC and recurrence tissues. Our IHC results showed that Sox2 and Lin28 were expressed in half of breast IDC patients¡¦ tumor tissue (49.6% and 49.7%, respectively), but Oct4 and Nanog are less expressed (13.5% and 24.7%, respectively). The protein expression levels of the four proteins were positively correlated with each other. In addition, the expression levels of the four proteins were upregulated in tumor adjacent normal tissue as compared to breast fibrosis pateints¡¦ normal mammary ductal tissue. To compare the expression levels of the four proteins in different tissues; such as tumor adjacent normal, DCIS, IDC and recurrence tissues, the expression levels of the four protiens gradually decreased when tumor developed and progressed. However, their expression levels were comparable between IDC and recurrence tissues. Additionally, the high expression levels of four proteins were high in two good clinicopathological characteristics and a biomarker of breast cancer; such as nuclear Sox2 and Lin28 in those with pathology stage I; nucleus expression of the four proteins in those with well and moderate cell differentiation; and Sox2 in those with positive estrogen receptor. However, the four proteins¡¦ expression levels were not correlated with IDC patients¡¦ survival. In conclusion, the reprogramming factors: Oct4, Sox2, Nanog and Lin28 may play an important role in tumorigenesis of breast IDC, but their impacts on tumor progression were quite small.

Solenopsis invicta, the red imported fire ant, has recently become associated with Antonina graminis, an invasive pest, and Neodusmetia sangwani, biological control agent, and maybe negatively affecting established biological control. A preliminary survey outlined the range of A. graminis and its parasitoids, and found N. sangwani was present at a reduced rate in South Texas and in the southeastern United States. A greenhouse experiment demonstrated that S. invicta decreased the rate of parasitism of A. graminis by N. sangwani, with S. invicta directly interfering with oviposition. Interactions between S. invicta and A. gaminis may be facilitating the spread and establishment of two invasive pests which has a negative impact on established classical biological control of A. graminis by N. sangwani.

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.

Invasive alien plants have impacted southern U.S. forests. This study focuses on quantifying current distribution, rate of dispersals, and economic losses caused by four major invaders — Chinese tallow (Triadica sebifera (L.) Small), Chinese Privet (Ligustrum sinense Lour.), European Privet (Ligustrum vulgare L.), and Japanese Honeysuckle (Lonicera japonica Thunb.). Using data from USDA Forest Service’s Forest Inventory and Analysis (FIA), National Oceanic and Atmospheric Administration (NOAA), and USGS Land Use and Land Cover (LULC), I first used logistic regressions to build occupation models for these four species. Second, I used VB.NET© (Microsoft, 2003) and Environment System Research Institute (ESRI) Arc View® 9.2 Geographical Information System (GIS) to model spatially explicit dispersal dynamics of these species. Finally, I evaluated economic losses associated with these invasions. The results of occupation models showed that landscape features, climatic conditions, forest and site conditions, forest management activities and disturbances, and forest ownership have statistically significant impacts on current distributions of all four species. The results of dispersal models showed that invasions of Chinese tallow, Chinese and European privets, and Japanese honeysuckle will be likely to appear on approximately 6.65 million acres of forest land in East Texas and Louisiana, 3.81 million acres in Mississippi and Alabama, and 12.55 million acres in Mississippi and Alabama, respectively, during the next 20 years. The estimated timber losses resulting from the invasion with no control for the next 20 years at 5% discount rate is 518 million dollars for Chinese tallow, 2.72 billion dollars for Chinese and European privets, and 11.05 billion dollars for Japanese honeysuckle. From an economic point of view, it would be most cost effective to execute high intensity control for these invasive species. Based on these findings, strategies for monitoring and mitigating these invasive species are proposed.

Reproduction de : Thèse d'exercice : Médecine : Nancy 1 : 2004. / Titre provenant de l'écran-titre.