Ecological specialization based on co-existence patterns is new methodology used for niche breadth measurement using co-existing community with occupancy data. It results in generalist-specialist continuum according to value of speciali- zation index. The aim of this thesis was testing index stability at spatial and tem- poral scale, compare this specialization index with other specialization indices and study changes in specialization with time changes in occupancy. Specialization was quantified using data of breeding birds atlases in the Czech Republic and Europe using two selected indices Theta and Simpson. Methodology seems to be sensitive to spatial scale. Instability appears at small scale for birds, stability and correlation between indices increase with gre- ater scale. Problems with using point counts corresponds to their unsuitability encompass birds' habitats, especially for water dependent birds. Correlations be- tween different time periods are stronger at greater spatial scale. Specialization based on co-existence patterns correlates with specialization according to experts' opinions. Results from comparing changes in specialization with changes in occu- pancy suggest, that most of species tend to leave more diverse sites with occupancy decline.

Este trabalho enfatizou as escalas espaciais de microhabitat e de mesohabitat para investigar como a fauna de macroinvertebrados aquáticos é influenciada pelas variáveis ambientais e espaciais. O primeiro capítulo trás uma visão geral da aplicabilidade das escalas de microhabitat e de mesohabitat ao avaliar a estrutura da fauna e, também, demonstra que a composição do substrato influencia a composição faunística. No segundo capítulo, realizamos uma avaliação da suficiência amostral e comparamos a diversidade alfa e beta entre métodos de coleta e entre diferentes mesohabitats. No terceiro capítulo avaliamos diferentes variáveis hidráulicas e suas relações com a abundância de indivíduos e a riqueza de táxons considerando as escalas espaciais de microhabitat e mesohabitat. Observamos que as condições hidráulicas foram importantes na estruturação da comunidade de macroinvertebrados, influenciando positivamente a abundância de indivíduos e negativamente a riqueza de táxons nos microhabitats. No quarto capítulo nos baseamos na teoria de metacomunidades para compreender a influência das variáveis ambientais e espaciais na estruturação da fauna em uma perspectiva de microescala. Além da esperada importância do ambiente para a microdistribuição dos organismos, identificamos uma forte influência do espaço na estruturação da fauna. Nossos resultados demonstraram que a fauna de macroinvertebrados aquáticos é estruturada pela composição do substrato, condições hidráulicas e fatores espaciais, todas estas condições perceptíveis na escala do microhabitat. Deste modo, a microescala pode ser considerada como uma perspectiva válida para o estudo de ecologia de riachos. / We focused on the microhabitat and the mesohabitat spatial scales to investigate the environmental and spatial features influence on aquatic macroinvertebrate fauna. The first chapter brings an overview about the microhabitat and mesohabitat applicability to evaluate the fauna structure. Likewise, it shows the substrate influence on the fauna composition. In the second chapter, we evaluate the sampling sufficiency and compare the alpha and beta diversity among the sampling methods and mesohabitats. In the third chapter we evaluated the hydraulic features and its relationships with abundance and richness considering the microhabitat and mesohabitat spatial scales. Our results show that the hydraulic conditions have influence on macroinvertebrate community structure, showing a positive relationship with abundance and negative with microhabitat richness. In the fourth chapter, we applied the metacommunity theory in the microhabitat scale to understand the hole of environmental and spatial features on the community structure. Further than the expected environmental influence on organisms microdistribution, we identified a strong spatial influence on the fauna structure. Our results showed that the aquatic macroinvertebrate fauna was structured by the substrate composition, hydraulic conditions and spatial features. All this conditions are noticeable on microhabitat spatial scale. Accordingly, the microhabitat scale can be considered as an effectual perspective to the stream ecology.

Abstract In this thesis I studied lotic trout predation and its ecological effects, and investigated invertebrate predator-prey interactions under natural and anthropogenically modified flow conditions. Given the growing concern about the reliability of extrapolations from small-scale studies to larger spatio-temporal scales, results of mechanistic small-scale experiments were scaled up by linking them to large-scale field surveys. An intensive survey assessed changes in diel feeding periodicity, prey selection and daily ration of juvenile brown trout (Salmo trutta L.) over the course of the open water period. This survey provides the first field estimates of juvenile brown trout daily rations and indicates crepuscular feeding peaks. Trout selectively preyed on medium- to large-sized prey, shifting towards epibenthic feeding with increasing availability of suitable prey. In a small-scale field experiment, trout displayed clear size-related predation concentrating on invertebrate predators and cased caddisflies, a pattern that scaled up successfully in large-scale surveys. Further, predation effects on large-sized prey were also repeated in a meta-analysis on lotic salmonid predation. While dense blackfly populations in lake-outlet streams are common, mass outbreaks of blackflies in short-term regulated rivers are poorly studied. In our studies the principal invertebrate predator of vernal benthic communities, the caseless caddisfly Rhyacophila, displayed significant preference for blackflies and was almost unable to capture any other prey, thus resulting in passive selection for larval blackflies. Rhyacophila larvae displayed highest capture success in intermediate current velocities, whereas further increases in current velocities decreased capture success. Short-term regulation releases increased both predator and prey drift but, unlike for Rhyacophila, magnitude of drift was unrelated to substrate for blackflies. Indeed, field observations indicated that blackflies rarely face detrimental effects of short-term regulation due to their fast growing rates and early emergence. Moss was the most preferred habitat of Rhyacophila and provided the best buffer against sudden increases in current velocities. These results suggest that several factors maintain spring-time outbreaks of blackfly populations in short-term regulated rivers: exaptation of the dominant blackfly species to prevailing conditions, degradation of the key habitat of the predator, and recurring annual drift losses and diminished capture success of Rhyacophila during short-term regulation releases.

Abstract Recognition of the importance of a regional perspective for understanding the structure and dynamics of local assemblages has stimulated the emergence of the field of macroecology. Most attention has been directed to terrestrial ecosystems, while large-scale patterns in biodiversity of aquatic organisms have received less attention. In this thesis I examined patterns of aquatic diversity across several geographic areas and scales, in an effort to understand some of the environmental and spatial factors determining species diversity in aquatic environments. The main objectives of this thesis were: (i) to examine the latitudinal diversity patterns of marine crustaceans and molluscs and their relationship to large scale environmental gradients, (ii) to study macroinvertebrate species richness in headwater streams at two spatial extents, within and across drainage systems, and assess the relative importance of local, landscape and regional variables, and (iii) to study diversity patterns of macroorganisms vs microorganism, comparing distance decay patterns of stream diatoms, macroinvertebrates and bryophytes. Latitudinal diversity patterns of crustaceans and molluscs were clearly related to larval developmental mode. An increase in species richness towards high latitudes was found for species with direct development, whereas richness of species with planktotrophic development decreased poleward. Sea surface temperature was the most important environmental gradient related to species richness of both phyla and each developmental mode, but with different effects on each mode. Stream macroinvertebrate species richness at the bioregion extent was negatively related to water humic content. Another factor related to species richness at the bioregion extent was elevation range, a variable linked to stream topographic heterogeneity. Local environmental variables explained most of the variation in species richness at the drainage system extent, however high among-region variability was evident. Patterns between macro- and microorganism may not be fundamentally different, but the level of environmental control varied, being strongest for diatoms, while some groups of benthic macroinvertebrates exhibited relatively strong dispersal limitation. The relative importance of niche vs. dispersal processes is not simply a function of organism size but other traits (e.g. life-history type, dispersal capacity) may obscure this relationship.

Deforestation and land use change are widespread in western Uganda. However, the spatial patterns and time-series of change and the reasons why it is occurring remain to be fully investigated. In this work a combination of satellite imagery and social surveys is used to quantify forest gains and loss over the last three decades in the region close to Lake Albert, whilst also providing an account of possible drivers of change. This area proves to be interesting as it covers regions with both formally protected areas (gazetted regions) and un-protected forest, the latter being largely under private ownership. Remote sensing data from the Landsat satellites were gathered for forest change detection, and were processed using standard remote sensing techniques, then quantified using GIS and regression methods. Fieldwork allowed these data to be ground truthed while gathering (quantitative) household surveys and (qualitative) key informant interviews. Quantitative surveys were analysed using Principal Components Analysis (PCA) and cluster analysis, and were compared qualitatively with the satellite analysis and stakeholder interviews. The results show that forest cover declined significantly outside gazetted areas at the expense of varying local?scale processes, although the protection of the gazetted forests was remarkably successful. In forest corridors outside gazetted regions, losses exceeded 90% (p<0.05). Survey data suggest that rural poor households were more likely to be situated in forested regions, and were more dependent on forest resources for their livelihoods. However, the drivers of change were spatially variable, with expansion of sugarcane farming being a likely driver in the northern areas, but small?scale agricultural expansion a significant factor in the more southern parts of the study region. While there is wide agreement within the data that the patterns of forest cover and land use changes are anthropogenically driven, more specific drivers are swamped by intricacies of the bio-physical and socio-economic preconditions that are inseparable in both space and time, although agricultural expansion and population growth were evident and pervasive. The analyses provide insights into complex anthropogenic processes at various spatial scales, and policy recommendations provided are widely applicable for developing countries struggling to conserve nature whilst boosting economic growth.

The introduction of species outside of their native ranges has been extensively studied in ecology. Particular attention has been paid to examining interactions between alien and native plants, and a large proportion of this attention has focused on pollinator-mediated interactions. In order to interact through pollinators, plants must co-occur, coflower, and share pollinators; studies investigating pollinator-mediated interactions between alien and native plants frequently make fundamental assumptions about the definition of these prerequisites to pollinator-mediated interaction. The present analysis examines assumptions about plant co-occurrence and the effects that these assumptions have on study outcomes. In Chapter 2, I present the results of a meta-analysis of 76 studies which overturns previous findings that pollinator-mediated interactions between plants can be predicted on the basis of whether the neighbour is an alien, phylogenetic distance, or floral trait similarity. Moreover, I demonstrate that the spatial definition of the control group (i.e. the distance between the group of focal plants that ‘do not co-occur’ with the alien/alternate neighbour species and the nearest individuals of that neighbour species), and the spatial arrangements of plants within their treatment groups (i.e. the relative placement of the group of focal plants that ‘co-occurr’ with the neighbour species), both have a significant impact on the outcome of pollinator-mediated interactions between alien and native plants. I also emphasize evidence of bias in the selection of study systems and in the process of publication. In Chapter 3, I present the results of a field experiment testing the role of distance between interacting plants in determining patterns of visitation by insects. The results of this analysis are suggestive of visitor functional group-dependent effects but limited by low power. In both Chapter 2 and Chapter 3, I show that heretofore unexamined assumptions about definitions of co-occurrence of plants may be introducing bias into studies of pollinator-mediated interactions between plants, and that facilitation and competition between plants for visitation may be linked across different spatial scales.

Society depends on bumblebees for the ecosystem service in the pollination of crops. Bumblebee declines have been documented, mostly due to intensification of agriculture and loss of species-rich semi-natural grasslands, an important bumblebee habitat. To conserve bumblebee diversity and the ecosystem service of pollination, it is important to do analyses on multiple spatial scales to see how the intensification of agriculture affects bumblebees at a landscape level. In this study, I related abundance of bumblebees in 476 sites in southern Sweden (total abundance and abundance of declining/non-declining, long-tongued/short-tongued, and species preferring open terrain vs. forest boundaries) to amount of land use types (semi-natural grassland, arable land, forest, water and “other land use”) at 34 spatial scales (radii 100 to 40,000 m). Arable land had a negative effect on total bumblebee abundance at scales from 464 to 10,000 m and forest had a negative effect at scales from 2929 to 5412 m. Semi-natural grassland showed no clear effects – however, the partial regression coefficients were consistently negative. Arable land had a negative effect on non-declining species, long- and short-tongued species and on species preferring forest boundaries at larger scales, e.g. regions dominated by agriculture. Forest had a positive effect at smaller scales on species preferring forest boundaries and a negative effect at larger scales on species preferring open terrain and on declining species. The results suggest that arable land is a non-habitat for bumblebees and that semi-natural grassland does not affect bumblebee abundance at a landscape level.

no / In normal vision, detecting a kink (a change in orientation) in a line is scale invariant: it depends solely on the length/width ratio of the line (D. Whitaker, D. M. Levi, & G. J. Kennedy, 2008). Here we measure detection of a change in the orientation of lines of different length and blur and show that strabismic amblyopia is qualitatively different from normal foveal vision, in that: 1) stimulus blur has little effect on performance in the amblyopic eye, and 2) integration of orientation information follows a different rule. In normal foveal vision, performance improves in proportion to the square root of the ratio of line length to blur (L: B). In strabismic amblyopia improvement is proportional to line length. Our results are consistent with a substantial degree of internal neural blur in first-order cortical filters. This internal blur results in a loss of scale invariance in the amblyopic visual system. Peripheral vision also shows much less effect of stimulus blur and a failure of scale invariance, similar to the central vision of strabismic amblyopes. Our results suggest that both peripheral vision and strabismic amblyopia share a common bottleneck in having a truncated range of spatial mechanisms-a range that becomes more restricted with increasing eccentricity and depth of amblyopia. / Leverhulme Trust, Wellcome Trust, NIH

No description available.

No description available.