Rapidly changing climates in northern Canada make the western Hudson Bay region an area of high importance for paleoenvironmental studies. Long-term changes in assemblages of diatoms (microscopic algae) were analyzed from lake sediment cores from Baker Lake, Nunavut, and Lake AT01, northern Ontario, to track responses to past environmental changes. Diatom assemblages dating to 6700 years ago in AT01 were initially characterized by cold- tolerant Fragilarioid assemblages, but shifted to an assemblage dominated by large benthic species and Cymbella diluviana consistent with the timing of the Holocene Thermal Maximum after 6300 years BP. A possible drainage event in Lake AT01 may have added significant hydrologic control on the diatom assemblages. The post-industrial period is marked by the largest compositional shifts in both records. Assemblages during the 20th century are indicative of reduced ice cover and enhanced thermal stratification linked to a climate regime shift noted in Hudson Bay since the mid-1990’s.

Amphibians harbor beneficial skin bacteria that can contribute to host defense against chytridiomycosis, an infectious disease caused by the lethal fungal pathogen Batrachochytrium dendrobatidis (Bd). However, while skin-associated microbial communities may alter host infection risk, the structure of these complex microbial communities can be impacted by both biotic and abiotic factors. In a series of three studies, I investigated the natural temporal and spatial variation in bacterial communities on the skin of wild and captive-born amphibians using 16S rRNA gene amplicon sequencing to characterize bacterial community diversity. First, in a study examining the skin bacterial communities of two sympatric treefrog species (Agalychnis callidryas and Dendropsophus ebraccatus) at a single pond over multiple seasons and years, I found that annual, seasonal, and even daily fluctuations in temperature and rainfall changed the skin bacterial communities on these species. Second, I further investigated the impact of seasonality and rainfall on amphibian skin bacterial communities with a study of the bacterial communities on Craugastor fitzingeri, a common terrestrial species, along a rainfall gradient, and five co-occurring amphibian species at a single site. The strong wet and dry seasonality in the tropical lowland forest impacted the bacterial communities of multiple stream-dwelling co-occurring species, but the nature of the changes differed among the frog species. For C. fitzingeri sampled along the rainfall gradient, I found there was variation in bacterial community structure among sites, although this was not correlated with the latitudinal rainfall gradient. Finally, I investigated the challenges faced by captive-reared Atelopus limosus, an endangered amphibian species, after soft-release into natural habitat with the use of mesocosms. I found that the skin bacterial communities reverted to wild-type fairly quickly, body condition decreased to come closer to wild conspecifics, and 15% of the frogs became infected with Bd during the 27 day trial in mesocosms. Overall, I found that skin bacterial communities of lowland amphibians change across time and space, that variation sometimes correlates with environmental conditions at the time and the site of sampling, and that skin bacterial communities on captive-born frogs revert to wild-frog's state soon after soft-release to natural habitat. / Doctor of Philosophy / Beneficial bacteria found on amphibian skin can provide protection against an infectious disease caused by the lethal amphibian chytrid fungus (Batrachochytrium dendrobatidis), that has been linked with the decline and extinction of amphibian species worldwide. However, while skin bacterial communities may play a key role in determining disease outcome, these complex microbial communities can be impacted by biological and environmental factors. In a series of three studies, I investigated the natural variation in skin bacterial communities on wild and captive-born amphibians through time and space using modern DNA sequencing technologies to characterize bacterial community diversity. First, in a study examining the skin bacterial communities of two treefrog species at a single pond over multiple years and seasons, I found that annual, seasonal, and even daily fluctuations in temperature and rainfall changed the skin bacterial communities on these species. Second, I further investigated the impact of seasonality and rainfall with a study sampling the skin of one common frog species along a rainfall gradient, and five amphibian species at a single site across seasons. The strong wet and dry seasonality in the tropical lowland forest impacted the bacterial communities of multiple species found near streams, but the nature of the changes differed among the different frogs. For the common species sampled along the rainfall gradient, I found there was variation in bacterial community structure among sites, although this was not correlated with the rainfall gradient. Finally, I investigated the challenges faced by captive-reared Atelopus limosus, an endangered amphibian species from Panama, after release into field enclosures in the natural habitat. I found that the skin bacterial communities reverted to wild-type fairly quickly, body mass decreased to come closer to wild frogs of the same species, and 15% of the frogs became infected with the chytrid fungus during the 27 day trial in the field enclosures. Overall, I found that skin bacterial communities of lowland amphibians change across time and space, that variation is sometimes linked with environmental conditions at the time and site of sampling, and that captive-born frogs revert to wild states soon after release to natural habitat.

No description available.

No description available.

Using archaeological and ethnohistorical data, this dissertation examines the character of the relationship between the Late Postclassic (ca. AD 1250-1520) frontier center of Totogal, located in the western Tuxtla Mountains (Toztlan) of southern Veracruz, Mexico, and the expanding Aztec Empire. Traditional models of imperialism examine frontiers from a core perspective that limits the autonomy and agency of groups in the path of expansion. Recent ethnographic, ethnohistoric, and archaeological studies of other boundaries, however, suggest that considerable room for negotiation exists within the space of interactions, whether asymmetrical amounts of power characterize the home bases of those groups. I argue that elites at Totogal, using imperial symbols and markers of their own high status, sponsored feasts and rituals for the non-elite public, during which they brokered the potentially conflicting interests of the Aztecs and the tribute paying population of the Tuxtlas. The invitation of the public to feasts and rituals that combined imperial and local elite symbols (and possibly green obsidian), naturalized the relationship between local elites and imperial representatives with non-elite occupants of Totogal and nearby settlements by establishing a reciprocal system of gifting whereby food and drink, served in the context of elaborate religious and commensal rituals, provided a benefit to the Tuxteco public which, along with other exotic highland goods, was viewed as an acceptable exchange for the local tribute items that the empire desired. This study is an important application of current anthropological perspectives on boundaries, borders, and frontiers to the Aztec Empire. It is also a critical examination of the types of strategies individuals and groups living in boundary regions can enact in situations of contact and change. While studies of modern groups in boundary regions have addressed identity construction and manipulation, and other dynamic social, political, and cultural processes that take place, they do not typically or systematically examine how the negotiations that are enacted in boundary zones are materialized—how changing identities are represented symbolically through the use of particular products or consumption patterns. It is in this area that archaeological perspectives on boundary zone interactions can make important contributions to the modern world.

Enquanto o mundo discute os esforços para combater as alterações climáticas globais, reconhece-se cada vez mais o papel vital das florestas na manutenção do bem-estar ecológico, social, econômico e cultural. Reafirma-se a importância da definição dos direitos de propriedade (posse e uso) sobre as florestas que pode determinar o seu destino. Para muitos países, as políticas de gestão de florestas combinam vários modos de acesso e gestão como i) áreas protegidas; ii) concessões florestais com critérios de gestão baseados em desempenho; iii) a devolução de áreas de florestas para as comunidades tradicionais e povos indígenas que farão sua gestão.O maior desafio é cumprir o planejado e implantar os diversos modos de gestão florestal para alcançar os objetivos sociais, econômicos e ambientais previstos face à pressão dos interesses econômicos internos e externos. A concessão de florestas é a forma dominante de gestão em quase todos os países da África Central e Ocidental. Ela também é o tipo dominante de exploração de florestas na Ásia (Malásia, Indonésia, Papua-Nova Guiné e Camboja). Na segunda metade dos anos 90, com o forte apoio de projetos de cooperação multilateral e de ONGs internacionais, a Bolívia introduziu a concessão florestal como um modo de conceder direitos de posse e uso sobre florestas. No Brasil, após duas tentativas fracassadas, o governo aprovou sua nova lei de gestão de florestas públicas em 2006. Bolívia e Brasil têm muito em comum em relação aos conflitos fundiários e desafios para impor novas regras relativas à maneira como as florestas podem ser exploradas nas suas regiões amazônicas, principalmente. Este trabalho de investigação centra-se sobre os principais obstáculos enfrentados pelas autoridades florestais bolivianas e brasileiras para implantar as concessões florestais na escala inicialmente prevista. O desenvolvimento do trabalho demandou a mobilização de duas correntes teórico-metodológicas. Por um lado, buscou-se um mapeamento dos modos pelos quais os indivíduos e grupos se apropriam e formulam regras para gerir porções de florestas. Por outro lado, a abordagem teórica da sociologia econômica, mais precisamente os trabalhos de Neil Fligstein e sua abordagem política-cultural, forneceu elementos para avaliar o processo de organização social da produção florestal madeireira nas duas regiões estudadas, que depende de quatro fatores: i) os direitos de propriedade, ii) as estruturas de governança, iii) as regras de troca e iv) as concepções de controle. A abordagem política-cultural considera a participação dos atores sociais como governos, empresas e consumidores, entre outros, e os incentivos para ações de cooperação com base nos laços cognitivos que os ligam. O estudo centrou-se na região amazônica de cada país: nas terras baixas bolivianas e, no Brasil, na região da rodovia Cuiabá-Santarém (BR-163). Isto porque estas regiões são os principais alvos para implantação de concessões florestais. Mostra-se neste estudo que sob um cenário de confusão fundiária, no qual há batalhas por pedaços dos territórios florestais e onde as alianças políticas são forjadas para favorecer outros padrões de uso das terras, a aplicação de concessões florestais em grande escala pode ser inviabilizada ou ficar bastante reduzida. / As the world is preparing to scale up its efforts to combat global climate change, groups are increasingly recognizing the vital role forests play in maintaining ecological, social, economic and cultural well-being. They are beginning to affirm more that forest tenure plays a fundamental role in determining the fate of the worlds forests. In many countries, questions are raised on whether tropical forests should be publicly, commonly or privately owned. For many countries the forest management policies will likely involve a combination of: i) protected areas of sufficient size to provide habitat protection, and in a contiguous pattern; ii) forest concessions with enforceable performance-based management criteria; iii) community forests and community forest concessions managed by communities and indigenous groups. The challenge is to undertake the land use planning commitment and implementation to achieve this in the face of pressure from internal and external interests. Forest concessions of various types are the dominant form of forest tenure in almost all the forest countries of West and Central Africa. They are also the dominant types of forest tenure in Asia (Malaysia, Indonesia, Papua New Guinea, and Cambodia). In South America, Peru and Bolivia introduced forest concession as a possible tenure model in the early 90s with the strong support of international NGOs. In Brazil, after two failed attempts, the government has passed its new forest management law in 2006. Bolivia and Brazil have much in common regarding forest tenure conflicts and challenges to enforce new rules in the forestry sector. Forest concession implementation in these countries has generated many expectations and investments in law changes.This research work focuses on the main barriers faced by Bolivian and Brazilian forest authorities in implementing forest concession on the scale initially planned. The studies required a mapping of the property rights regimes over forest and forest resources as well as a theoretical approach of economic sociology. This approach, which provides elements to evaluate the process of social market construction, is dependent upon four essential factors: property rights, governance structures, rules of exchange and conceptions of control. The political-cultural approach emphasizes the historic perspective of the markets to understand the role of dominant groups and challengers in action arenas. It also considers the participation of social actors like governments, firms and consumers, among others, and their incentives for cooperative actions based on the cognitive ties that bind them. This empiric study focused on each countrys geographically-delimited regions of Amazon: in the Bolivian lowlands region and in the Brazilian Cuiabá-Santarém Highway (namely BR-163). Thats because they are the main targets for forest concession implementation. We show in this study that under a tenure uncertainty scenario, in which there are battles for territorial pieces and political alliances are forged that prefer other land use (and forests uses also) patterns the forest concessions implementation on a large scale will be jeopardized in these territories.

This study investigates the ecology of one of the best known Australian marsupials, the Common Brushtail Possum Trichosurus vulpecula, in central Australia. Trichosurus vulpecula is one of few medium-sized mammal species that persist in arid Australia today. Its distribution within the arid zone has declined markedly since European settlement. Two populations, one within the East MacDonnell Ranges along the Hale River and the other on Irving Creek, a River Red Gum creek in the Petermann Ranges, were studied in the southern Northern Territory. Others locations in the region were visited opportunistically. Trie central Australian Trichosurus is not distinct genetically from populations elsewhere in Australia. The diet of T. vulpecula consisted of a range of leaves, flowers and fruits of perennial dicotyledonous species as well as some ephemeral herbs. Grasses were absent from the diet. Variation in the diet reflected seasonal availability in flowers and fruits. The species preferentially consumed at each site had significantly higher moisture content and dry matter digestibility than species not consumed. Preferred species included Amyema maidenii leaves (a mistletoe), Acacia spp. flowers and fruits, Santalum lanceolatum leaves (a shrub), Marsdenia australis leaves (a vine), Solarium quadriloculatum fruit (shrub) and Euphorbia spp. leaves (herb). Small amounts of invertebrate material were consumed throughout the year. Other non-plant material consumed included honeycomb and unfledged birds eg. Budgerigars. There were no significant differences in the diet between the sexes. Trichosurus vulpecula were found in six main habitats: Acacia aneura/Callitris glaucophylla on rocky hills; E. camaldulensis sandy creek-lines; mixed Acacia rocky hills, Rocky Eucalyptus creek-lines; Degraded drainage lines; and Wet gullies. Logistic regression modelling revealed a significant correlation between mistletoe species richness, higher levels of soil nitrogen and the presence of T. vulpecula. In habitats occupied by T. vulpecula species richness of mistletoes was associated with the absence of fire and the presence of reliable ground water supplies. Trichosurus vulpecula were highly mobile with mean home ranges at Hale River of 44.21 � 22.76 ha and considerably higher than those recorded in previous studies in Australia. Mean home ranges at Irving Creek were much smaller, at 4.99 � 1.46 ha and VII similar to that recorded in other studies in Australia. At both sites, males had larger home ranges and there was a high degree of overlap with other males and females. At the Hale River study site, T. vulpecula predominantly denned in caves or cavities in rocks, whereas at Irving Creek all den sites were in large Eucalyptus camaldulensis on the drainage line. Adult and pouch young sex ratios were at parity. During this study, T. vulpecula was found to breed continuously, with births recorded in almost all months. Growth of the young were more rapid than previously recorded for Trichosurus in Australia. This is interpreted as an adaptation for living in an arid environment, enabling the young to achieve independence before quality food supplies diminish. No single exotic predator or competitor was solely responsible for the decline of T. vulpecula in arid Australia, implying an interactive impact. Prey switching by dingoes from rabbits to T. vulpecula, macropods and echidnas followed the crash of rabbit populations at Hale River. Predation by dingoes on T. vulpecula was only recorded once, at the Irving Creek study site, where numbers of rabbits remained stable throughout the study. The impact of exotic herbivores occurred through habitat degradation rather than competition. Evaluation of the ecological data collected during this study generally supports current models of decline and extinction in medium-sized mammals in arid Australia, integrating the effects of predators, competitors, drought and fire. However, the importance of each factor on populations of T. vulpecula was found to vary depending on their location in the landscape. This study suggests two separate models to explain the decline of T. vulpecula in arid Australia after the arrival of Europeans. The first operates in the riparian lowlands and the second on the rocky ranges. In both models, prior to European settlement, T. vulpecula occupied refuge habitats characterised by readily available moisture for plant growth (run on areas and/or shallow water tables) and soils with higher soil nutrient concentrations. The impact of fires on these refugia was minimal, as Aboriginal burning practices protected them with mosaic burning generally preventing large-scale fires from developing. Following European settlement, the forces impacting on populations were different in the riparian lowlands from those affecting rocky ranges. In the riparian lowlands, the effects of rabbits and livestock together with predation were found to have the major impact on T. vulpecula populations. Fire was not a significant factor in these areas. In the rocky ranges, fire was the most significant factor affecting T. vulpecula populations. Introduced herbivores did not degrade these habitats as they did in the riparian lowlands because the rugged and steep nature of the ranges acted as a physical barrier. Similarly, predator numbers were lower because of the relative difficulty in moving over rough ground and the generally lower relative abundance of preferred prey such as rabbits. An adaptive management strategy needs to be implemented to determine the effects of different management regimes on T. vulpecula population viability. The key elements of a management strategy in the riparian lowlands involves the manipulation and monitoring of predators, rabbits and livestock numbers. In the rocky ranges, the key management strategy involves the implementation of a patch burning to prevent fires entering habitats occupied by T. vulpecula. Importantly, any management strategies should involve Aboriginal people. Trichosurus vulpecula is an important part of Aboriginal culture. Its decline is of great concern to many people and several of the remaining populations and potential reintroduction locations are on Aboriginal land. Because of their relationship with the land and the animals, people have both the knowledge of the animal and the skills (such as patch burning) to provide information to managers which will assist with management. To achieve these management directions a coordinated national education programme is required to inform and convince the Australian community that conservation of T. vulpecula is deserving of attention in arid and semi-arid Australia. This is particularly important given the perception that T. vulpecula is a common species throughout Australia, despite its massive decline in arid Australia since European settlement.

The repercussions of climate change are felt worldwide, but Arctic and subarctic regions, where climate warming is expected to be amplified, are especially vulnerable. An episode of mass fish mortality in the Sutton River in the Hudson Bay Lowlands (HBL) of Northern Ontario has elicited the interest of the scientific community. Several lakes were sampled over three years in an effort to better understand and document the changes that may be occurring in these lakes. This study uses sediment cores to assess the history of mercury (Hg) deposition and to assess changes occurring in autochthonous productivity in these lakes. Sediments deposited after the onset of the industrial revolution contained significantly higher concentrations of Hg, with the highest concentrations found in the most recently deposited sediments. Hg concentrations in these pristine lakes rival those of lakes in heavily urbanized areas, indicating that they are in fact subjected to atmospheric deposition of Hg. There was a large variation in [Hg] of the surface sediments of 13 lakes; underscoring the importance of in situ processes in the fate of atmospherically deposited Hg. Methylmercury (MeHg) concentrations were not correlated with total mercury concentrations (THg), demonstrating how THg is a poor predictor of MeHg; the bioaccumulative neurotoxic form of mercury. The S2 fraction of Rock-Eval® Pyrolysis, C:N ratios and ∂13C signatures were used as proxies of autochthonous carbon and all indicated that the lakes have become increasingly productive, presumably due to warmer water temperatures and longer ice-free seasons. Additionally, I use molecular techniques to detect and quantify the merA gene in the sediment; a proxy of bacterial mercury resistance involved in redox transformations. In Aquatuk, Hawley and North Raft Lakes, I observed a subsurface increase in merA genes in the sediment core, independently of a control gene and the [THg]. While I have not been able to explain the driving variables of this subsurface increase, I believe that the role of merA within remote lake sediments deserves further work. Lastly, microcosms were used to measure the production of volatile elemental mercury (Hg(0)) from surface sediments of Aquatuk Lake. I used a combination of analytical and molecular techniques to show that the production of Hg(0) is biogenic and tested the effect of nutrients, pH and ionic strength on the Hg(0) production rates. Ionic strength alone had the greatest impact on Hg(0) production rates, with increased Hg(0) production as ionic strength increases.

Recent research has shown that the Arctic may be a sink for mercury, however, the fate of this deposited mercury in the environment is not known. The objective of this project was to determine the factors affecting methyl mercury (MeHg) production in Arctic organic soil on the Truelove Lowlands, Devon Island, Canada. In the field we observed a steady decrease in MeHg over time, with MeHg concentration at many sampling locations declining below detection limits. This decrease did not correlate to any chemical or biophysical parameter measured. During the study the Lowlands appeared to be mildly reducing with dissolved Fe(II) being present in the porewater, however, no correlation was observed between MeHg production and the variables measured. The dissolved organic matter concentration of the porewater was quite high, the pH was circumneutral and it would seem that in the absence of more highly reducing conditions that mercury would be unavailable for methylation.<p> It seems likely under field conditions MeHg was much more bioavailable then inorganic mercury. This would lead to a higher rate of demethylation then methylation and a net decrease in MeHg. Little research has been done on demethylation and the effect of environmental conditions on demethylation, especially in arctic environments. However, it is possible that the rate of demethylation was not affected by changes in temperature or any other parameter measured over the course of the field study. <p> Laboratory microcosm studies using saturated soil from the organic horizons demonstrated little potential for unspiked organic soil to produce significant amounts of MeHg. The spiked treatment, however, had an eight fold increase in MeHg concentration and the sterile treatment showed no change in MeHg concentration over 40 days of freeze (-5 0C) and 59 days of thaw (4 oC). <p> Our data suggests that a combination of atmospheric and in-situ processes maintain a cycle of MeHg production (spring) and loss (summer) in arctic soils. It would seem that Arctic wetland soils are not a significant source of MeHg to the Arctic ecosystem and that snowmelt is the dominant source.

Recent research has shown that the Arctic may be a sink for mercury, however, the fate of this deposited mercury in the environment is not known. The objective of this project was to determine the factors affecting methyl mercury (MeHg) production in Arctic organic soil on the Truelove Lowlands, Devon Island, Canada. In the field we observed a steady decrease in MeHg over time, with MeHg concentration at many sampling locations declining below detection limits. This decrease did not correlate to any chemical or biophysical parameter measured. During the study the Lowlands appeared to be mildly reducing with dissolved Fe(II) being present in the porewater, however, no correlation was observed between MeHg production and the variables measured. The dissolved organic matter concentration of the porewater was quite high, the pH was circumneutral and it would seem that in the absence of more highly reducing conditions that mercury would be unavailable for methylation.<p> It seems likely under field conditions MeHg was much more bioavailable then inorganic mercury. This would lead to a higher rate of demethylation then methylation and a net decrease in MeHg. Little research has been done on demethylation and the effect of environmental conditions on demethylation, especially in arctic environments. However, it is possible that the rate of demethylation was not affected by changes in temperature or any other parameter measured over the course of the field study. <p> Laboratory microcosm studies using saturated soil from the organic horizons demonstrated little potential for unspiked organic soil to produce significant amounts of MeHg. The spiked treatment, however, had an eight fold increase in MeHg concentration and the sterile treatment showed no change in MeHg concentration over 40 days of freeze (-5 0C) and 59 days of thaw (4 oC). <p> Our data suggests that a combination of atmospheric and in-situ processes maintain a cycle of MeHg production (spring) and loss (summer) in arctic soils. It would seem that Arctic wetland soils are not a significant source of MeHg to the Arctic ecosystem and that snowmelt is the dominant source.