Topological redundancy and ‘small‐world’ patterns in a food web in a subtropical ecosystem of Brazil          下载免费PDF全文

Hugo Bornatowski  Rodrigo Barreto  Andrés F. Navia  Alberto Ferreira de Amorim 《Marine Ecology》2017,38(2)

According to graph theory, the frequency distribution of trophic interactions within a food web has deep structural implications, as it can highlight the presence of patterns associated with the web and indicate whether the properties of the web are independent of its size. A hypothesis is that ‘small‐world’ food webs are sensitive to the loss of species with the highest values. Therefore, the present work aimed to evaluate the degree to which a subtropical food web in Southern Brazil displays small‐world patterns and their resistance. As part of the assessment, we evaluated the topological redundancy values of species in the food web and then we simulated the exclusion of these species (such as sharks and sea birds), and also the exclusion of high centrality species (such as squids Loligo sp., portunid swimming crabs and the cutlassfish Trichiurus lepturus). The food web showed a ‘broad‐scale’ distribution of connections by node, and a small‐world pattern. As expected, a simplification of the network was observed after elimination of some species with high centrality. However, the food web was resistant to the loss of species with low topological redundancy, probably because these species occupy a high trophic level and do not participate in lots of routes within the food web. We highlight however, the importance of the application of multiple analyses to evaluate the importance of components in food webs, and fisheries management plans should consider both species of high centrality values and species with low topological redundancy.  相似文献   

Trace-element heterogeneity in rutile linked to dislocation structures: Implications for Zr-in-rutile geothermometry     

Rick Verberne  Hugo W. van Schrojenstein Lantman  Steven M. Reddy  Matteo Alvaro  David Wallis  Denis Fougerouse  Antonio Langone  David W. Saxey  William D. A. Rickard 《Journal of Metamorphic Geology》2023,41(1):3-24

The trace-element composition of rutile is commonly used to constrain P–T–t conditions for a wide range of metamorphic systems. However, recent studies have demonstrated the redistribution of trace elements in rutile via high-diffusivity pathways and dislocation-impurity associations related to the formation and evolution of microstructures. Here, we investigate trace-element migration in low-angle boundaries formed by dislocation creep in rutile within an omphacite vein of the Lago di Cignana unit (Western Alps, Italy). Zr-in-rutile thermometry and inclusions of quartz in rutile and of coesite in omphacite constrain the conditions of rutile deformation to around the prograde boundary from high pressure to ultra-high pressure (~2.7 GPa) at temperatures of 500–565°C. Crystal-plastic deformation of a large rutile grain results in low-angle boundaries that generate a total misorientation of ~25°. Dislocations constituting one of these low-angle boundaries are enriched in common and uncommon trace elements, including Fe and Ca, providing evidence for the diffusion and trapping of trace elements along the dislocation cores. The role of dislocation microstructures as fast-diffusion pathways must be evaluated when applying high-resolution analytical procedures as compositional disturbances might lead to erroneous interpretations for Ca and Fe. In contrast, our results indicate a trapping mechanism for Zr.  相似文献