The overarching objective of this dissertation was to improve our knowledge of the relationship between seascape heterogeneity and diversity of stony coral assemblages across spatial scales. Coral communities on patch reefs in three regions of the Caribbean were used as a model system to investigating this relationship because patch reef heterogeneity could be readily quantified within the seascape using remote sensing and image analysis techniques. I began with a theoretical approach, exploring the origins of observed species diversity among coral communities at increasing spatial scales. Hierarchical sampling and null models revealed that coral diversity was governed by non-random processes at local- (10s of meters) and meso- (100s of m) scales. Spatial autocorrelation and reef heterogeneity were then investigated as potential mechanistic drivers of these non-random diversity patterns. I found limited support for spatial drivers. However, beta diversity was significantly correlated to metrics of reef heterogeneity (measured as reef size, spatial configuration, and complexity), indicating that differences in reef heterogeneity were making a disproportionate contribution to the overall coral community diversity. The relationship between corals and reef heterogeneity was found to be both scale-dependent and region dependent. This theoretical approach was followed by a manipulative approach using an existing artificial patch reef array to experimentally test the influence of reef spatial configuration and topographical complexity on local diversity. Corals were most sensitive to reef size and secondarily reef configuration within the seascape. Unlike reef fishes, reef complexity did not emerge as a strong predictor of the coral community composition in either the observational data or the experimental manipulation. These observational and experimental explorations of the relationship between corals and habitat reveal that intra-habitat variability (i.e. differences between patch reefs) can influence the diversity and abundance of corals. I then focused on applying this improved theoretical understanding towards improving coral management efforts. I present a new methodology to assess the efficacy of marine reserve effects by controlling for natural seascape variation within and beyond the reserve boundary, and I quantified the bias of underestimating coral diversity by using conventional reef monitoring protocols that ignore differences in reef size. In conclusion, I demonstrate empirically that seascape attributes of reef heterogeneity can contribute to coral diversity at relatively small spatial scales (<1km) and can affect corals with different life history traits in different ways. Hence, management and conservation efforts must consider the role of these meso-scale spatial metrics to influence the structure of the coral assemblage at the local scale.

Den här studien tar upp problematiken med fragmentering och dess påverkan på arters spridning och förekomst. Huvudsyftet med studien var att testa teorin om öbiogeografi genom att undersöka förekomsten av ett antal kärlväxter på olika åkerholmar med olika avstånd till närmaste spridningskälla i form av ett bryn i en närliggande skog. Vi har inventerat 40 stycken par av åkerholmar (öar) och skogsbryn (fastland) i ett jordbrukslandskap i Stockholms län. Inventeringsresultatet har analyserats med hjälp av univeriata linjära modeller-, och multiveriat ordination. Resultatet visar att teorin om öbiogeografi bara delvis kan förklara förekomstmönster för kärlväxter på åkerholmar. Vidare fann vi att spridningen av arter begränsas av åkerholmens storlek. Avstånd hade en effekt på artsammansättningen på åkerholmar. Vårt resultat visar på ett behov av att se till fragmentsstorlek samt grad av isolering som viktiga faktorer som styr möjligheten för att arter i framtiden ska kunna sprida sig till nya habitat. / This study address the problem of fragmentation, and its impact on species distribution and abundance. The main aim of the study was to test the theory of island biogeography using plant species prevalence from field islets at different distances from nearest “mainland”. We have studied 40 pairs of field islets (islands) and forest edges (mainland) in agricultural landscapes in the Stockholm County. The result of the inventory was analyzed using univariate linear models-, and multivariate ordination. Our result show that the theory of island biogeography partly can explain species prevalence patterns, but not all of them. Furthermore, we found that species distributions were limited by the size of the field islets. Distance from mainland had an effect on the species composition in the field islets. Our results indicate a need to include the size of habitat fragments, and the degree of isolation as important factors determining the ability for future species dispersal to newly established habitats.

Um dos padrões mais importantes que ocorrem em ecossistemas é a relação espécie-área, que relaciona o número de espécies em um ecossistema com a sua área disponível. O estudo dessa relação é fundamental para entender-se a biodiversidade e o impacto de políticas ambientais de preservação de espécies, de modo que é possível analisar desde os tamanhos das reservas necessários para a conservação das espécies e até verificar o impacto da intervenção humana em habitats naturais. Assim sendo, várias estratégias matemáticas e computacionais foram desenvolvidas para prever e entender esse padrão ecológico em modelos ecológicos. Todavia, muitas abordagens são simuladas em ambientes homogêneos e regulares, porém, sabe-se que, em cada ecossistema, há regiões com acidentes geográficos, variações de altitudes, vegetação e clima. Dessa forma, nesse trabalho, estamos interessados em estudar a influência de diferentes ambientes no processo de evolução das espécies. Para isso, consideramos modelos ecológicos que utilizam características geográficas para colonização e, comportamentos individuais como dispersão, mutação, acasalamento. Com isso, foi possível simular a propagação das espécies em diferentes topologias e analisar como ocorreu a dinâmica em cada uma delas. Assim, verificamos que a topologia regular e a dispersão homogênea dos indivíduos são duas características que maximizam a diversidade de espécies. E por outro lado, a formação de regiões mais densas e interações heterogêneas, contribuem para a diminuição da quantidade de espécies, apesar de em alguns casos, ajudarem na velocidade de propagação e colonização. / One of the most important patterns that occur in ecosystems is the species-area relationship, which says that the number of species increases with the sampled area. There is a great interest among ecologists about this pattern, since it is possible to verify the human impact on the environment and the area of reserves necessary to maintain species. Thus, motivated by the explanation of such behavior, some mathematical and computational strategies have been developed over the years. However, most approaches are simulated in homogeneous and regular scenarios, however, in the ecosystem, there are regions with landforms, different climates and vegetation. Thus, in this work, we are interested in studying the influence of different environments in the evolution process of the species. We consider ecological models that use geographical characteristics for colonization and individual behaviors such as dispersion, mutation, and mating. Thereby, it was possible to simulate the propagation of the species in different topologies and to analyze how the dynamics occurred in each case. Therefore, we verified that the regular topology and the homogeneous dispersion of the individuals are two characteristics that maximize the diversity of species. On the other hand, denser regions and heterogeneous interactions, contribute to the decrease the number of species, even when in some cases, they help in the speed of propagation and colonization.

The species–area relationship (SAR) has been applied to predict species richness declines as area is converted to human-dominated land covers.In many areas of the world, however, many species persist in human-dominated areas, including threatened species. Because SARs are decelerating nonlinear, small extents of natural habitat can be converted to human use with little expected loss of associated species, but with the addition of more species that are associated with human land uses. Decelerating SARs suggest that, as area is converted to human-dominated forms, more species will be added to the rare habitat than are lost from the common one. This should lead to a peaked relationship between richness and natural area. I found that the effect of natural area on avian richness across Ontario was consistent with the sum of SARs for natural habitat species and human-dominated habitat species, suggesting that almost half the natural area can be converted to human-dominated forms before richness declines. However, I found that this spatial relationship did not remain consistent through time: bird richness increased when natural cover was removed (up to 4%), irrespective of its original extent. The inclusion of metapopulation processes in predictive models of species presence improves predictions of diversity change through time dramatically. Variability in site occupancy was common among bird species evaluated in this study, likely resulting from local extinction-colonization dynamics. Likelihood of species presence declined when few neighbouring sites were previously occupied by the species. Site occupancy was also less likely when little suitable habitat was present. Consistent with expectations that larger habitats are easier targets for colonists, habitat area was more important for more isolated sites. Accounting for the effect of metapopulation dynamics on site occupancy predicted change in richness better than land cover change and increased the strength of the regional richness–natural area relationship to levels observed for continental richness–environment relationships suggesting that these metapopulation processes “scale up” to modify regional species richness patterns making them more difficult to predict. It is the existence of absences in otherwise suitable habitat within species’ ranges that appears to weaken regional richness–environment relationships.

The species–area relationship (SAR) has been applied to predict species richness declines as area is converted to human-dominated land covers.In many areas of the world, however, many species persist in human-dominated areas, including threatened species. Because SARs are decelerating nonlinear, small extents of natural habitat can be converted to human use with little expected loss of associated species, but with the addition of more species that are associated with human land uses. Decelerating SARs suggest that, as area is converted to human-dominated forms, more species will be added to the rare habitat than are lost from the common one. This should lead to a peaked relationship between richness and natural area. I found that the effect of natural area on avian richness across Ontario was consistent with the sum of SARs for natural habitat species and human-dominated habitat species, suggesting that almost half the natural area can be converted to human-dominated forms before richness declines. However, I found that this spatial relationship did not remain consistent through time: bird richness increased when natural cover was removed (up to 4%), irrespective of its original extent. The inclusion of metapopulation processes in predictive models of species presence improves predictions of diversity change through time dramatically. Variability in site occupancy was common among bird species evaluated in this study, likely resulting from local extinction-colonization dynamics. Likelihood of species presence declined when few neighbouring sites were previously occupied by the species. Site occupancy was also less likely when little suitable habitat was present. Consistent with expectations that larger habitats are easier targets for colonists, habitat area was more important for more isolated sites. Accounting for the effect of metapopulation dynamics on site occupancy predicted change in richness better than land cover change and increased the strength of the regional richness–natural area relationship to levels observed for continental richness–environment relationships suggesting that these metapopulation processes “scale up” to modify regional species richness patterns making them more difficult to predict. It is the existence of absences in otherwise suitable habitat within species’ ranges that appears to weaken regional richness–environment relationships.

It is generally assumed that when natural habitat is converted to human-dominated cover such area is “lost” to its native species. Extinctions will ensue. The literature generally assumes that species are extirpated as natural area is reduced, following the well-known species-area relationship (SAR). However, SARs have consistently over-estimated species losses resulting from conversion of natural habitat to human-dominated land covers. We hypothesize that the overestimation occurs because these area-based models assume that converted habitat is “lost”, eliminating all species. However, in the real world, conversion of natural land cover to human-dominated cover frequently produces new land covers, different from the original habitat, but not necessarily completely inhospitable to biodiversity. We evaluated the responses of total avian richness, forest bird richness and open habitat bird richness to remaining natural area within 991 quadrats, each 100 km2, across southern Ontario. Total bird species richness does not follow SAR predictions; rather, the number of bird species peaks at roughly 50% natural land cover. The richness of forest birds does follow the usual SAR power-law as a function of forested area. In contrast, richness of birds that prefer open-habitat does not increase monotonically with either natural- or human-dominated land cover. However, we can partition human-dominated land cover into an “available human-dominated” component and “lost” habitat. Richness of open-habitat species relates to the amount of available human-dominated cover. Distinguishing three habitat types (natural, available human-dominated, and lost) permits accurate predictions of species losses in response to natural habitat conversion.

The species–area relationship (SAR) has been applied to predict species richness declines as area is converted to human-dominated land covers.In many areas of the world, however, many species persist in human-dominated areas, including threatened species. Because SARs are decelerating nonlinear, small extents of natural habitat can be converted to human use with little expected loss of associated species, but with the addition of more species that are associated with human land uses. Decelerating SARs suggest that, as area is converted to human-dominated forms, more species will be added to the rare habitat than are lost from the common one. This should lead to a peaked relationship between richness and natural area. I found that the effect of natural area on avian richness across Ontario was consistent with the sum of SARs for natural habitat species and human-dominated habitat species, suggesting that almost half the natural area can be converted to human-dominated forms before richness declines. However, I found that this spatial relationship did not remain consistent through time: bird richness increased when natural cover was removed (up to 4%), irrespective of its original extent. The inclusion of metapopulation processes in predictive models of species presence improves predictions of diversity change through time dramatically. Variability in site occupancy was common among bird species evaluated in this study, likely resulting from local extinction-colonization dynamics. Likelihood of species presence declined when few neighbouring sites were previously occupied by the species. Site occupancy was also less likely when little suitable habitat was present. Consistent with expectations that larger habitats are easier targets for colonists, habitat area was more important for more isolated sites. Accounting for the effect of metapopulation dynamics on site occupancy predicted change in richness better than land cover change and increased the strength of the regional richness–natural area relationship to levels observed for continental richness–environment relationships suggesting that these metapopulation processes “scale up” to modify regional species richness patterns making them more difficult to predict. It is the existence of absences in otherwise suitable habitat within species’ ranges that appears to weaken regional richness–environment relationships.

Central Europe wet meadows are characterized by considerable species richness. The biodiversity maintenance of the wet meadows is connected with regular management (i.e. grazing or mowing). As their area drastically decreased due to changes in land use in the last century, they have become the object of interest among scientists, conservation biologists. This thesis is composed of three original studies which are focused on escribing diversity patterns of the whole spectra of wet meadows at landscape level and dynamic of their changes depending on different management regimes (mowing/abandonment,fertilizing/unfertilizing). The synthesis of these studies reveals the description of the processes underlying the wet meadows species loss depending on land use changes and proposes the principles for sustainable conservation management.

Um dos padrões mais importantes que ocorrem em ecossistemas é a relação espécie-área, que relaciona o número de espécies em um ecossistema com a sua área disponível. O estudo dessa relação é fundamental para entender-se a biodiversidade e o impacto de políticas ambientais de preservação de espécies, de modo que é possível analisar desde os tamanhos das reservas necessários para a conservação das espécies e até verificar o impacto da intervenção humana em habitats naturais. Assim sendo, várias estratégias matemáticas e computacionais foram desenvolvidas para prever e entender esse padrão ecológico em modelos ecológicos. Todavia, muitas abordagens são simuladas em ambientes homogêneos e regulares, porém, sabe-se que, em cada ecossistema, há regiões com acidentes geográficos, variações de altitudes, vegetação e clima. Dessa forma, nesse trabalho, estamos interessados em estudar a influência de diferentes ambientes no processo de evolução das espécies. Para isso, consideramos modelos ecológicos que utilizam características geográficas para colonização e, comportamentos individuais como dispersão, mutação, acasalamento. Com isso, foi possível simular a propagação das espécies em diferentes topologias e analisar como ocorreu a dinâmica em cada uma delas. Assim, verificamos que a topologia regular e a dispersão homogênea dos indivíduos são duas características que maximizam a diversidade de espécies. E por outro lado, a formação de regiões mais densas e interações heterogêneas, contribuem para a diminuição da quantidade de espécies, apesar de em alguns casos, ajudarem na velocidade de propagação e colonização. / One of the most important patterns that occur in ecosystems is the species-area relationship, which says that the number of species increases with the sampled area. There is a great interest among ecologists about this pattern, since it is possible to verify the human impact on the environment and the area of reserves necessary to maintain species. Thus, motivated by the explanation of such behavior, some mathematical and computational strategies have been developed over the years. However, most approaches are simulated in homogeneous and regular scenarios, however, in the ecosystem, there are regions with landforms, different climates and vegetation. Thus, in this work, we are interested in studying the influence of different environments in the evolution process of the species. We consider ecological models that use geographical characteristics for colonization and individual behaviors such as dispersion, mutation, and mating. Thereby, it was possible to simulate the propagation of the species in different topologies and to analyze how the dynamics occurred in each case. Therefore, we verified that the regular topology and the homogeneous dispersion of the individuals are two characteristics that maximize the diversity of species. On the other hand, denser regions and heterogeneous interactions, contribute to the decrease the number of species, even when in some cases, they help in the speed of propagation and colonization.

The species–area relationship (SAR) has been applied to predict species richness declines as area is converted to human-dominated land covers.In many areas of the world, however, many species persist in human-dominated areas, including threatened species. Because SARs are decelerating nonlinear, small extents of natural habitat can be converted to human use with little expected loss of associated species, but with the addition of more species that are associated with human land uses. Decelerating SARs suggest that, as area is converted to human-dominated forms, more species will be added to the rare habitat than are lost from the common one. This should lead to a peaked relationship between richness and natural area. I found that the effect of natural area on avian richness across Ontario was consistent with the sum of SARs for natural habitat species and human-dominated habitat species, suggesting that almost half the natural area can be converted to human-dominated forms before richness declines. However, I found that this spatial relationship did not remain consistent through time: bird richness increased when natural cover was removed (up to 4%), irrespective of its original extent. The inclusion of metapopulation processes in predictive models of species presence improves predictions of diversity change through time dramatically. Variability in site occupancy was common among bird species evaluated in this study, likely resulting from local extinction-colonization dynamics. Likelihood of species presence declined when few neighbouring sites were previously occupied by the species. Site occupancy was also less likely when little suitable habitat was present. Consistent with expectations that larger habitats are easier targets for colonists, habitat area was more important for more isolated sites. Accounting for the effect of metapopulation dynamics on site occupancy predicted change in richness better than land cover change and increased the strength of the regional richness–natural area relationship to levels observed for continental richness–environment relationships suggesting that these metapopulation processes “scale up” to modify regional species richness patterns making them more difficult to predict. It is the existence of absences in otherwise suitable habitat within species’ ranges that appears to weaken regional richness–environment relationships.