Publicação
Biogeography and macroecology of spiders along a gradient of mediterraneity
| Resumo: | The dunes of the Atlantic coast of the Iberian Peninsula have been recognized as a priority area for conservation due to the large number of rare or endemic species. However, coastal dunes are one of the most threatened systems due to human disturbance, such as urbanization and tourism, and climatic changes. Understanding the determinants of biodiversity distribution patterns is crucial for the development of efficient conservation strategies and management of coastal dunes. In this thesis, spider distribution patterns were studied in coastal dunes along a gradient of mediterraneity. The main aims were: (1) to characterize biogeographic patterns of spiders; (2) to evaluate the relative effects of environmental and spatial variables and their scale-specific importance on species richness gradients and beta diversity patterns of spider assemblages; (3) to determine the relative contribution of species turnover and species richness differences to the emergence of beta diversity patterns along biogeographic, latitudinal and ecological gradients. The study was carried out in 18 coastal dune sites along the western coast of the Iberian Peninsula. This area encompasses 445 km and comprises two distinct biogeographic regions, Eurosiberian (Northern coast) and Mediterranean (Centre and South). A standardized and optimized sampling protocol developed for Mediterranean spiders was used. In chapter II, biogeographic patterns of spiders assemblages were studied. The western coast of the Iberian Peninsula is a “biogeographic crossroad”, encompassing faunistic elements of different origins (Wide-range, Eurosiberian, Mediterranean and Iberian). Cluster analysis, ANOSIM tests and NMDS showed that spider assemblages were structured along a gradient from North to South, forming four geographically distinct clusters. A hierarchic typology of sites was constructed and several indicator species were found for the different levels of the typology. The biogeographic patterns of spider assemblages provide evidence that both current (e.g. climate) and historic factors have had a profound effect on the distribution of species along the Atlantic coast of the Iberian Peninsula. In chapter III and chapter IV the determinants of species richness and beta diversity patterns, respectively, were evaluated. Variation partitioning and principal coordinates of neighbour matrices (PCNM) were used in order to estimate the contribution of pure environmental and pure spatial effects and their shared influence on the observed patterns and to estimate the relative importance of environmental structured variation and pure spatial variation at multiple spatial scales. 72.8% of species richness variation could be explained by the environmental (climate and dune stability) and spatial variables. Most of this variation corresponds to the environmental-spatially structured component (51.3%). The influence of environmental variables was scale-dependent. At the broadest scales, the latitudinalclimatic gradient was the dominant factor, whilst at the finest scale, stability of the dune system was the most important component. A combination of environmental and PCNM variables explained 46.1% of the variation of beta diversity patterns. Most of this variation (42.5%) corresponded to spatial variation (environmental spatially structured and pure spatial). Climate and vegetation structure influences were predominant at the PCNM1 and PCNM3 scales, while area was more important at the intermediate PCNM2 scale. Hence, the results reinforced the importance of the incorporation of both local and broad-scale factors when examining beta diversity patterns. In Chapter V, a novel approach that disentangles all compositional differences (βcc, overall beta diversity) in its two origins, species turnover (β-3, species replacement) and species richness differences (βrich, species loss/gain) is proposed. The performance of the novel method was tested in different theoretical gradients with known values of species replacement and loss and real scenarios differing in their nature and complexity. This framework allowed discriminating different causes of the beta diversity patterns along latitudinal, biogeographic or ecological gradients. |
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| Autores principais: | Carvalho, José Carlos Lopes de |
| Ano: | 2011 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso restrito |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The dunes of the Atlantic coast of the Iberian Peninsula have been recognized as a priority area for conservation due to the large number of rare or endemic species. However, coastal dunes are one of the most threatened systems due to human disturbance, such as urbanization and tourism, and climatic changes. Understanding the determinants of biodiversity distribution patterns is crucial for the development of efficient conservation strategies and management of coastal dunes. In this thesis, spider distribution patterns were studied in coastal dunes along a gradient of mediterraneity. The main aims were: (1) to characterize biogeographic patterns of spiders; (2) to evaluate the relative effects of environmental and spatial variables and their scale-specific importance on species richness gradients and beta diversity patterns of spider assemblages; (3) to determine the relative contribution of species turnover and species richness differences to the emergence of beta diversity patterns along biogeographic, latitudinal and ecological gradients. The study was carried out in 18 coastal dune sites along the western coast of the Iberian Peninsula. This area encompasses 445 km and comprises two distinct biogeographic regions, Eurosiberian (Northern coast) and Mediterranean (Centre and South). A standardized and optimized sampling protocol developed for Mediterranean spiders was used. In chapter II, biogeographic patterns of spiders assemblages were studied. The western coast of the Iberian Peninsula is a “biogeographic crossroad”, encompassing faunistic elements of different origins (Wide-range, Eurosiberian, Mediterranean and Iberian). Cluster analysis, ANOSIM tests and NMDS showed that spider assemblages were structured along a gradient from North to South, forming four geographically distinct clusters. A hierarchic typology of sites was constructed and several indicator species were found for the different levels of the typology. The biogeographic patterns of spider assemblages provide evidence that both current (e.g. climate) and historic factors have had a profound effect on the distribution of species along the Atlantic coast of the Iberian Peninsula. In chapter III and chapter IV the determinants of species richness and beta diversity patterns, respectively, were evaluated. Variation partitioning and principal coordinates of neighbour matrices (PCNM) were used in order to estimate the contribution of pure environmental and pure spatial effects and their shared influence on the observed patterns and to estimate the relative importance of environmental structured variation and pure spatial variation at multiple spatial scales. 72.8% of species richness variation could be explained by the environmental (climate and dune stability) and spatial variables. Most of this variation corresponds to the environmental-spatially structured component (51.3%). The influence of environmental variables was scale-dependent. At the broadest scales, the latitudinalclimatic gradient was the dominant factor, whilst at the finest scale, stability of the dune system was the most important component. A combination of environmental and PCNM variables explained 46.1% of the variation of beta diversity patterns. Most of this variation (42.5%) corresponded to spatial variation (environmental spatially structured and pure spatial). Climate and vegetation structure influences were predominant at the PCNM1 and PCNM3 scales, while area was more important at the intermediate PCNM2 scale. Hence, the results reinforced the importance of the incorporation of both local and broad-scale factors when examining beta diversity patterns. In Chapter V, a novel approach that disentangles all compositional differences (βcc, overall beta diversity) in its two origins, species turnover (β-3, species replacement) and species richness differences (βrich, species loss/gain) is proposed. The performance of the novel method was tested in different theoretical gradients with known values of species replacement and loss and real scenarios differing in their nature and complexity. This framework allowed discriminating different causes of the beta diversity patterns along latitudinal, biogeographic or ecological gradients. |
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