The minimum ecologically viable population size (MEVP) of a species describes the minimum size at which the species itself or another species in the same ecosystem goes extinct as a result of the loss of inter-specific interactions. The MEVP shows a good potential for use as a tool for exploring the mechanisms behind species extinctions, but presently only a small amount of research has been done that takes advantage of this. In this study the MEVP is used to investigate what properties of species can be used as good indicators of ecological importance. 100 large computer generated food webs were created with an assembly model and the reduction in density that was necessary to induce an extinction event in the web was subsequently determined for each species within the webs. This change in density was then correlated with 28 different properties, measured for each species. The results show that properties that measure how well connected a species is, as well as measures of the species role as a prey item in the web are the ones with the greatest potential to find species with high MEVP. Further, the results put emphasis on the importance of regarding the web as a whole when working with species extinctions, while also highlighting the usefulness of the MEVP concept.

No description available.

People are active participants in coral reef ecosystems. This ethnobiology study considers and contrasts folkbiological knowledge of people living in two groups of artisanal fishing villages in Kadavu Province, Fiji. The high level of biological diversity on the Astrolabe Reef provides insights into folk categorization and classification methods that include colour, shape, size, physical features, and habits of certain reef fish and marine animals. Surveying large numbers of experts and novices on defined groups of creatures yields more depth and range of responses allowing higher confidence levels in response accuracy. A comparison of the data with Berlins (1992) proposed principles yields mixed results. Sea cucumbers have high ecological salience and their identification requires attention to the affect of two centuries of trade on Fijian society. Effective ethnobiological research provides productive options to contribute to coral reef sustainability programs with long term benefits for local people and marine life. Key words: Kadavu, naming and classification of fish, coral reef ethnobiology.

Ficus (Moraceae) é o gênero mais importante para animais frugívoros nas florestas tropicais, considerado um recurso-chave durante períodos de escassez de frutos. Esses animais dispersam suas sementes e contribuem para a manutenção das populações de figueiras. A perda de hábitat e a fragmentação da paisagem podem afetar a sobrevivência de populações e a composição de comunidades e suas interações. Os objetivos deste trabalho foram (1) comparar a frugivoria e a dispersão de sementes por aves frugívoras entre espécies de Ficus encontradas em remanescentes de Floresta Estacional Semidecidual e (2) testar se a perda de hábitat influencia a frugivoria e dispersão de sementes dessas árvores. Estudamos três áreas de reservas florestais no Estado de São Paulo, sudeste do Brasil, com diferentes áreas e nível de fragmentação da paisagem: Parque Estadual do Morro do Diabo (33.845 ha), Estação Ecológica dos Caetetus (2.176 ha) e Estação Ecológica de Ribeirão Preto (180 ha). Ao longo de 443 h de observação árvore-focal, registramos todas as espécies de aves frugívoras se alimentando de figos e estimamos a taxa de remoção de figos e sementes. Como nossos dados não se adequaram a métodos estatísticos tradicionais, utilizamos a reamostragem por bootstrap para estimar os intervalos de confiança das taxas de remoção e dispersão de sementes e testar as diferenças entre as espécies de figueira e as áreas de estudo. Trinta e duas espécies de aves foram observadas consumindo figos de seis espécies de Ficus. As figueiras que apresentam figos verdes, de tamanho médio ou grande, foram consumidas por uma boa variedade de espécies, mas apenas uma das aves de cada assembléia foi responsável pela remoção da maior parte dos figos. Ficus luschnathiana, com figos pequenos e vermelhos quando maduros, foi consumida de forma mais equitativa pelos seus visitantes, e apresentou taxa de dispersão de sementes significativamente maior que as demais espécies. A fragmentação reduziu a remoção de figos e sementes de F. citrifolia. Ficus eximia não demonstrou nenhum padrão claro, uma vez que só teve um consumo expressivo em um microhábitat específico, não incluído na análise da fragmentação. No fragmento menor, aves de grande porte, consideradas bons dispersores de sementes, não foram encontradas e as aves menores e generalistas não compensaram a perda do serviço de dispersão de sementes. Essas espécies de Ficus, no entanto, devem depender mais de morcegos e macacos-prego que das aves no processo de dispersão, e devem inclusive ser beneficiadas pelo aumento na extensão de bordas. Mesmo que essa comunidade de figueiras no fragmento menor não estabeleça uma interação forte com a avifauna, ainda é relevante testar se a baixa densidade de indivíduos de F. luschnathiana é consequencia da ausência de bons dispersores de sementes. / Ficus (Moraceae) is the most important plant genus for tropical frugivores and is considered a keystone resource during periods of general fruit scarcity. Frugivorous animals disperse their seeds and contribute for the maintenance of fig trees populations. Habitat loss and landscape fragmentation can affect species survival as well as community composition and their interactions. The goals of this study were (1) to compare the frugivory and seed dispersal by frugivorous birds among Ficus species found in Semideciduous Seasonal Forest remnants and (2) to assess whether habitat loss influences frugivory and seed dispersal of these trees. We studied three natural reserves in São Paulo State, southeastern Brazil, which differ in area and landscape fragmentation: Morro do Diabo State Park (33.845 ha), Caetetus Ecological Station (2.176 ha) and Ribeirão Preto Ecological Station (180 ha). During 443 h focal tree observation, we registered all frugivorous birds eating figs and estimated their fruit removal and seed dispersal. As traditional statistical methods were not suitable for our data, we used bootstrap data resampling to estimate confidence limits of fruit removal and seed dispersal and test for differences between fig trees and forest fragments. A total of 32 bird species were observed consuming figs of six Ficus species. Fig trees bearing green-fruited and medium or large figs were consumed by a great diversity of birds, but showed a dominance of only one species over the others on the fruit removal. Ficus luschnathiana, whose figs are small and red when ripe, was more equally consumed by all visitors and had significantly more seeds dispersed per hour than the other species. Fragmentation reduced fruit removal and seed dispersal of F. citrifolia. Ficus eximia did not show a clear pattern, once it was only highly consumed by birds in a specific microhabitat not included on the fragmentation analysis. The effect upon other Ficus species remains to be tested. In the smallest forest remnant, large-bodied birds, considered high quality seed dispersers, cannot be found anymore and small and generalist birds are not able to compensate for this loss on seed dispersal service. These Ficus species, however, may depend more upon bats and capuchin monkeys than on birds for seed dispersal, and may even benefit from the increase in extension of forest edges. Even if this Ficus community as a whole does not seem to interact with birds, it remains relevant, though, to test whether F. luschnathiana\'s low density in the smallest fragment is due to the absence of good seed dispersers.

The subject of this diploma thesis is an analysis of the historical existence of European bison in the Czech geographical region and an evaluation of the significance of its presence to the surrounding landscape. The goal of the thesis is to depict bison population changes in the Czech territory over time and the meaning of efforts to reintroduce the bison into its natural habitat. An important part of the work then will be the preparation, realization and evaluation of two excursions during which students go for European bison directly into the field.

Ficus (Moraceae) é o gênero mais importante para animais frugívoros nas florestas tropicais, considerado um recurso-chave durante períodos de escassez de frutos. Esses animais dispersam suas sementes e contribuem para a manutenção das populações de figueiras. A perda de hábitat e a fragmentação da paisagem podem afetar a sobrevivência de populações e a composição de comunidades e suas interações. Os objetivos deste trabalho foram (1) comparar a frugivoria e a dispersão de sementes por aves frugívoras entre espécies de Ficus encontradas em remanescentes de Floresta Estacional Semidecidual e (2) testar se a perda de hábitat influencia a frugivoria e dispersão de sementes dessas árvores. Estudamos três áreas de reservas florestais no Estado de São Paulo, sudeste do Brasil, com diferentes áreas e nível de fragmentação da paisagem: Parque Estadual do Morro do Diabo (33.845 ha), Estação Ecológica dos Caetetus (2.176 ha) e Estação Ecológica de Ribeirão Preto (180 ha). Ao longo de 443 h de observação árvore-focal, registramos todas as espécies de aves frugívoras se alimentando de figos e estimamos a taxa de remoção de figos e sementes. Como nossos dados não se adequaram a métodos estatísticos tradicionais, utilizamos a reamostragem por bootstrap para estimar os intervalos de confiança das taxas de remoção e dispersão de sementes e testar as diferenças entre as espécies de figueira e as áreas de estudo. Trinta e duas espécies de aves foram observadas consumindo figos de seis espécies de Ficus. As figueiras que apresentam figos verdes, de tamanho médio ou grande, foram consumidas por uma boa variedade de espécies, mas apenas uma das aves de cada assembléia foi responsável pela remoção da maior parte dos figos. Ficus luschnathiana, com figos pequenos e vermelhos quando maduros, foi consumida de forma mais equitativa pelos seus visitantes, e apresentou taxa de dispersão de sementes significativamente maior que as demais espécies. A fragmentação reduziu a remoção de figos e sementes de F. citrifolia. Ficus eximia não demonstrou nenhum padrão claro, uma vez que só teve um consumo expressivo em um microhábitat específico, não incluído na análise da fragmentação. No fragmento menor, aves de grande porte, consideradas bons dispersores de sementes, não foram encontradas e as aves menores e generalistas não compensaram a perda do serviço de dispersão de sementes. Essas espécies de Ficus, no entanto, devem depender mais de morcegos e macacos-prego que das aves no processo de dispersão, e devem inclusive ser beneficiadas pelo aumento na extensão de bordas. Mesmo que essa comunidade de figueiras no fragmento menor não estabeleça uma interação forte com a avifauna, ainda é relevante testar se a baixa densidade de indivíduos de F. luschnathiana é consequencia da ausência de bons dispersores de sementes. / Ficus (Moraceae) is the most important plant genus for tropical frugivores and is considered a keystone resource during periods of general fruit scarcity. Frugivorous animals disperse their seeds and contribute for the maintenance of fig trees populations. Habitat loss and landscape fragmentation can affect species survival as well as community composition and their interactions. The goals of this study were (1) to compare the frugivory and seed dispersal by frugivorous birds among Ficus species found in Semideciduous Seasonal Forest remnants and (2) to assess whether habitat loss influences frugivory and seed dispersal of these trees. We studied three natural reserves in São Paulo State, southeastern Brazil, which differ in area and landscape fragmentation: Morro do Diabo State Park (33.845 ha), Caetetus Ecological Station (2.176 ha) and Ribeirão Preto Ecological Station (180 ha). During 443 h focal tree observation, we registered all frugivorous birds eating figs and estimated their fruit removal and seed dispersal. As traditional statistical methods were not suitable for our data, we used bootstrap data resampling to estimate confidence limits of fruit removal and seed dispersal and test for differences between fig trees and forest fragments. A total of 32 bird species were observed consuming figs of six Ficus species. Fig trees bearing green-fruited and medium or large figs were consumed by a great diversity of birds, but showed a dominance of only one species over the others on the fruit removal. Ficus luschnathiana, whose figs are small and red when ripe, was more equally consumed by all visitors and had significantly more seeds dispersed per hour than the other species. Fragmentation reduced fruit removal and seed dispersal of F. citrifolia. Ficus eximia did not show a clear pattern, once it was only highly consumed by birds in a specific microhabitat not included on the fragmentation analysis. The effect upon other Ficus species remains to be tested. In the smallest forest remnant, large-bodied birds, considered high quality seed dispersers, cannot be found anymore and small and generalist birds are not able to compensate for this loss on seed dispersal service. These Ficus species, however, may depend more upon bats and capuchin monkeys than on birds for seed dispersal, and may even benefit from the increase in extension of forest edges. Even if this Ficus community as a whole does not seem to interact with birds, it remains relevant, though, to test whether F. luschnathiana\'s low density in the smallest fragment is due to the absence of good seed dispersers.

Species-species and species-habitat interactions have been demonstrated to be important in influencing diversity across a variety of ecosystems. Despite generalities in the importance of these interactions, appropriate mechanisms to explain them are absent in many systems. In sandhill systems of the southeast U.S., gopher tortoises have been hypothesized to be a crucial species in the maintenance of diversity and function. However, the mechanisms and magnitude in which they influence their communities and habitats have rarely been empirically quantified. I examined how habitat structure influences tortoise abandonment of burrows and how tortoise densities influence nonvolant vertebrate community diversity. Tortoise burrow abandonment is directly influenced by canopy closure, with each percent increase in canopy cover relating to a ~2% increase in the probability of burrow abandonment. In addition, tortoise burrow density was positively correlated with diversity and evenness, but not species richness. This influence was directly proportional to burrow density, supporting a dominance role for this species and rejecting the commonly asserted keystone species mechanism. I also quantified the influence of tortoises in influencing diversity relative to other environmental and habitat variables. Through this research, I have demonstrated that disturbance and habitat structure are important, but diversity responds most to density of burrows in the habitat. These findings demonstrate the intricate relationships interacting to maintaining diversity in sandhill systems. In particular, habitat change leading to declines of gopher tortoises may have drastic negative impacts on vertebrate species diversity.

No description available.

Cavity-nesting communities are structured by the creation of and competition for cavities as nest-sites. Viewing these communities as interconnected webs can help identify species interactions that influence community structure. This study examines cavity-nesting bird community interactions within the fire-maintained longleaf pine (Pinus palustris) ecosystem at Eglin Air Force Base, Florida. In chapter 1, I provide a background review of the ecology of my study system. In chapter 2, I use nest webs to depict the flow of cavity-creation and use at Eglin. I identified 2 webs into which most species could be placed. One web contained 6 species associated with pines. The second web contained 5 species associated with hardwoods. Red-cockaded woodpeckers (Picoides borealis) and northern flickers (Colaptes auratus) created most cavities used by other species within this community. In chapter 3, I describe snag densities and nest-site selection of the cavity-nesting bird community at Eglin. Large, mature pine snags were abundant, exceeding other reported densities for southern pine forests. Pine snags were heavily-used, despite the abundance of available red-cockaded woodpecker cavities in living pine. Hardwood snags accounted for 10% of nests found, and were used by 12 of 14 species. Diameters of nest-trees and available snags were below the range of optimal nest-snag diameters reported in other studies, indicating the need for site-specific snag management guidelines. In chapter 4, I combine a study of basic ecological principles with endangered species management to examine interactions within the cavity-nesting bird community at Eglin. I used a nest web to identify a potential indirect interaction between the red-cockaded woodpecker and large secondary cavity-nesters, mediated by the northern flicker. I used structural equation modeling to test a path model of this interaction. By experimentally manipulating cavity availability, I blocked links described in the model, confirming cavity creation and enlargement as mechanisms that influence this indirect relationship. I demonstrated that a red-cockaded woodpecker cavity-management technique could disrupt this indirect relationship by affecting northern flicker behavior, and provided an empirical example of how, in interactive ecological communities, single-species management can have indirect effects on non-target species. / Ph. D.

Cette thèse avait pour objectif principal d'approfondir nos connaissances sur l'écologie des différents types de milieux humides lacustres afin d'optimiser leur conservation. Pour ce faire, j’ai étudié la résilience, les fonctions et les services écologiques (FSE), ainsi que la biodiversité de trois types de milieux humides lacustres. Ces milieux humides sont riverains au lac Papineau, qui est situé dans la réserve naturelle de Kenauk Nature, entre les Laurentides et l’Outaouais. Cette thèse combine des approches globales, multifonctionnelles et ciblées, axées sur la conservation des milieux humides et de leur biodiversité. Dans mon premier chapitre, j'ai d’abord identifié les déterminants écologiques de la typologie des trois types de milieux humides étudiés : des tourbières, des aulnaies (marécages arbustifs) et des frênaies (marécages arborescents). À l’aide de données récoltées sur le terrain et de données cartographiques, j'ai quantifié 12 prédicteurs hydrogéomorphologiques (HGM) et j'ai pu identifier la pente et l'élévation comme étant les déterminants écologiques les plus importants. Mes résultats ont également apporté des nuances supplémentaires quant aux variables associées à chaque type de milieu humide. En utilisant ces 12 prédicteurs HGM, j'ai créé un modèle de forêts d’arbres décisionnels capable de prédire à la fois la présence des milieux humides lacustres et leur typologie. Ce modèle a permis de prédire avec une précision de 89 % la typologie des sites étudiés, ce qui en fait un outil intéressant pour étudier la répartition des milieux humides riverains à d'autres lacs. J'ai également utilisé ce modèle pour simuler différents scénarios de changements du niveau d'eau, mettant en évidence la résilience des tourbières et des aulnaies, ainsi que la vulnérabilité des frênaies, aux changements globaux. Dans mon second chapitre, j'ai quantifié huit FSE à l'aide de 25 indicateurs différents, dont 15 ont été quantifiés à partir de données terrain. J'ai ensuite développé une approche multifonctionnelle permettant d'étudier simultanément toutes les interactions de synergies et de compromis entre les indicateurs de FSE et les trois types de milieux humides. Mes résultats ont montré que chaque type de milieu humide maximise différentes FSE, mais que le choix des indicateurs influence considérablement les patrons de synergies et de compromis. Bien que certains types de milieux humides maximisent les mêmes FSE, ils le font à travers différents mécanismes écologiques. Enfin, la biodiversité floristique et faunique (plantes, oiseaux, poissons, zooplanctons et insectes chanteurs) présentait les patrons d'interaction les plus diversifiés, chaque type de milieu humide maximisant différents aspects de la biodiversité. Dans mon troisième chapitre, j'ai optimisé l'approche des espèces clés (keystone species) pour permettre son utilisation en conservation afin d’identifier les espèces indicatrices de la biodiversité. Pour cela, je me suis basée sur l’approche la plus récente proposée dans la littérature et j'ai identifié les éléments qui limitaient son utilisation pour les praticiens et les praticiennes. J'ai ensuite proposé des modifications pour surmonter ces limites. Ces modifications ont permis : 1) d'élargir l'utilisation de cette approche aux données d'inventaires terrain, 2) d'identifier les espèces ayant un impact négatif sur la biodiversité, et 3) de définir des seuils rigoureux pour identifier les espèces clés au sein d'une communauté. J'ai ensuite testé cette approche sur les communautés de plantes, d'oiseaux et de poissons des milieux humides échantillonnés dans le cadre de cette thèse. Mes résultats ont montré que cette approche permettait d'identifier des espèces possédant effectivement des caractéristiques écologiques expliquant leur importance dans l'augmentation ou la diminution de la biodiversité. Ensemble, les trois approches présentées dans cette thèse offrent une perspective intégratrice de la conservation des milieux humides lacustres. Les méthodes qui y sont proposées représentent des outils intéressants, qui ont le potentiel d’optimiser notre gestion du territoire à court et à long terme, mais aussi à petite et à grande échelle. / The main objective of this thesis was to deepen our understanding of the ecology of different types of lake-edge wetlands to optimize their conservation. To achieve this, I studied the resilience, the ecosystem functions and services (EFS), and the biodiversity of three types of lake-edge wetlands. All studies wetlands were riverine to Lake Papineau, which is located in a Kenauk Nature natural reserve, between the Laurentides and Outaouais regions. This thesis therefore combines a global, a multifunctional, and a targeted approach, all focused on wetland conservation. In my first chapter, I first identified the ecological determinants of the typology of the three types of wetlands studied: peatlands, alder swamps (shrub swamps), and ash swamps (trees swamps). Using both data collected on the field and map data, I quantified 12 hydrogeomorphological (HGM) predictors and identified slope and elevation as the most important ecological determinants. My results also provided additional nuances regarding the variables associated with each wetland type. Using these 12 HGM predictors, I then created a Random Forest model capable of predicting both the presence of lake-edge wetlands and their typology. This model predicted the typology of the studied sites with 89 % accuracy, making it an interesting tool to study the distribution of lake-edge wetlands along the shore of other lakes. I also used this model to simulate different scenarios of water level changes, highlighting the resilience of peatlands and alder swamps, as well as the vulnerability of ash swamps, to global changes. In my second chapter, I quantified eight EFS using 25 different indicators, with 15 indicators quantified using field data. I developed a multifunctional approach to simultaneously study all the synergies and trade-offs between the EFS indicators and the three wetland types. My results showed that each wetland type maximizes different EFS, and that the choice of indicators significantly influences the patterns of synergies and trade-offs. Although some wetland types maximized the same EFS, they do so through different ecological mechanisms. Finally, biodiversity exhibited the most diverse interaction patterns, with each wetland type maximizing different aspects of it. In my third chapter, I optimized the keystone species approach to allow its use in conservation to identify indicator species for biodiversity monitoring. To do so, I relied on the most recent approach proposed in the literature and identified the elements that limited its use for practitioners. I then proposed modifications to overcome these limitations. These modifications allowed 1) to expand the use of this approach to field inventory data, 2) to identify species that have a negative impact on biodiversity, and 3) to define rigorous thresholds to identify keystone species within a community. I then tested this approach on plant, bird, and fish communities in the wetlands sampled in this thesis. My results showed that this approach effectively identified species with ecological characteristics that explained their importance in increasing or decreasing biodiversity. Together, the three approaches presented in this thesis provide an integrative perspective on the conservation of lake-edge wetlands. The methods I propose represent interesting tools that have the potential to optimize land management in the short and long term, as well as at small and large scales.