Padrões espaciais de biodiversidade e estabilidade da abundância de espécies ao longo de gradientes ambientais

Abstract

Growing anthropogenic pressures on earth, particularly those related to urbanizationand agricultural intensification, have resulted in the loss and fragmentation of habitats, with possible consequences for biodiversity and ecosystem stability. However, there is still limited understanding of how different taxonomic groups respond to these pressures andat what spatial scale these effects are strongest. Another uncertainty concerns the level of spatiotemporal change of the different dimensions of biodiversity (e.g., taxonomicand functional). The main goal of this thesis was to evaluate how anthropogenic impactsaffect patterns of diversity and stability of species abundance at multiple spatial scales. For that, we used databases of hundreds of animal metacommunities, collected with high spatial and temporal resolution and through international collaborations from several Europeancountries. This thesis is divided into three chapters. In the first, we investigated howthe relationships between dispersal ability and body size of six groups of arthropods influence therelative amount of β-diversity components: species replacement and nestedness (variationinspecies composition resulting from difference of species richness between communities). For this type of analysis, urban gradients were considered, which were quantified at multiplespatial scales. We found that groups with a positive relationship between body size anddispersal ability showed a more pronounced nestedness pattern towards urban centers comparedto groups that showed a neutral relationship between size and dispersal ability, mainlyat the local scale. This result is in agreement with our hypotheses and indicates that not onlyissize an important attribute that influences species selection along the urban gradient, but that variation in dispersal capacity also influences the organization of urban metacommunities, implying different regional management strategies. In the second chapter, we assessthe prevalence of biotic homogenization and differentiation mainly in Western Europe andrelate these patterns to various functional attributes of butterflies. For this, we usedspecies abundance data collected during a minimum of four and a maximumof twelve yearsand integrated with functional attributes of butterflies in seven European countries. We foundan increase in the proportion of species with greater thermal tolerance and egg volumeinmost metacommunities, regardless of taxonomic and functional homogenization or differentiation scenarios. Finally, in the third chapter, we use the same butterfly data to assess howdifferent facets of diversity and abiotic factors affect the stability of butterflies’ abundance at multiple scales. Our results provide the first evidence that both local stability and communities asynchronous dynamics drive regional stability of butterfly abundance, but withrelatively greater importance of the former component. We found that climatic factors (temperatureand precipitation) and spatial distance modulated the stabilizing effect of different facetsof biodiversity, mainly in a positive way. We found that functional β-diversity and the different facets of α-diversity were important drivers of maintaining regional stability. Wealso demonstrate that there is a relative change in the contribution of local and regional stabilizing processes depending on the dispersal ability of butterflies. Particularly, species withlow dispersal capacity have higher functional β-diversity and metapopulational andspatial asynchrony, which contributes to regional stability. On the other hand, communitiesof species with high dispersal capacity present greater α-diversity (taxonomic and functional), which results in a stronger contribution of local mechanisms on the stabilityof metacommunities. Overall, our results indicate that (i) structural and functional connectivity modulates the responses of taxa to environmental disturbances; (ii) the trend observedfor species with broad climatic tolerance and larger egg size, considering the different homogenization and differentiation scenarios, suggests that climatic extremes seemtobethe strongest filter in the structuring of butterfly communities and that larger egg sizemaybe associated with factors that positively influence larval survival and (iii) mobility changesthe relative importance of local and regional stabilizing processes. Furthermore, we emphasize the necessary consideration of multiple spatial scales to improve understandingof biodiversity change along disturbance gradients and their stabilizing effect, withdirect implications for conservation and management.