19 research outputs found

    Considering the Case for Biodiversity Cycles: Reexamining the Evidence for Periodicity in the Fossil Record

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    Medvedev and Melott (2007) have suggested that periodicity in fossil biodiversity may be induced by cosmic rays which vary as the Solar System oscillates normal to the galactic disk. We re-examine the evidence for a 62 million year (Myr) periodicity in biodiversity throughout the Phanerozoic history of animal life reported by Rohde & Mueller (2005), as well as related questions of periodicity in origination and extinction. We find that the signal is robust against variations in methods of analysis, and is based on fluctuations in the Paleozoic and a substantial part of the Mesozoic. Examination of origination and extinction is somewhat ambiguous, with results depending upon procedure. Origination and extinction intensity as defined by RM may be affected by an artifact at 27 Myr in the duration of stratigraphic intervals. Nevertheless, when a procedure free of this artifact is implemented, the 27 Myr periodicity appears in origination, suggesting that the artifact may ultimately be based on a signal in the data. A 62 Myr feature appears in extinction, when this same procedure is used. We conclude that evidence for a periodicity at 62 Myr is robust, and evidence for periodicity at approximately 27 Myr is also present, albeit more ambiguous.Comment: Minor modifications to reflect final published versio

    Income redistribution in the European Union

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    We explore the redistributive effects of taxes and benefits in the 27 member states of the European Union (EU) using EUROMOD, the tax-benefit microsimulation model for the EU. As well as describing redistributive effects in aggregate, we assess and compare the effectiveness of eight individual types of policy in reducing income disparities. We derive results for the 27 members of the EU using policies in effect in 2010 and present them for each country separately as well as for the EU as a whole

    Multifractal Spatial Patterns and Diversity in an Ecological Succession

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    We analyzed the relationship between biodiversity and spatial biomass heterogeneity along an ecological succession developed in the laboratory. Periphyton (attached microalgae) biomass spatial patterns at several successional stages were obtained using digital image analysis and at the same time we estimated the species composition and abundance. We show that the spatial pattern was self-similar and as the community developed in an homogeneous environment the pattern is self-organized. To characterize it we estimated the multifractal spectrum of generalized dimensions Dq. Using Dq we analyze the existence of cycles of heterogeneity during succession and the use of the information dimension D1 as an index of successional stage. We did not find cycles but the values of D1 showed an increasing trend as the succession developed and the biomass was higher. D1 was also negatively correlated with Shannon's diversity. Several studies have found this relationship in different ecosystems but here we prove that the community self-organizes and generates its own spatial heterogeneity influencing diversity. If this is confirmed with more experimental and theoretical evidence D1 could be used as an index, easily calculated from remote sensing data, to detect high or low diversity areas

    A new measure of longitudinal connectivity for stream networks

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    Habitat connectivity is a central factor in shaping aquatic biological communities, but few tools exist to describe and quantify this attribute at a network scale in riverine systems. Here, we develop a new index to quantify longitudinal connectivity of river networks based on the expected probability of an organism being able to move freely between two random points of the network. We apply this index to two fish life histories and evaluate the effects of the number, passability, and placement of barriers on river network connectivity through the use of simulated dendritic ecological networks. We then extend the index to a real world dendritic river system in Newfoundland, Canada. Our results indicate that connectivity in river systems, as represented by our index, is most impacted by the first few barriers added to the system. This is in contrast to terrestrial systems, which are more resilient to low levels of connectivity. The results show a curvilinear relationship between barrier passability and structural connectivity. This suggests that an incremental improvement in passability would result in a greater improvement to river network connectivity for more permeable barriers than for less permeable barriers. Our analysis of the index in simulated and real river networks also showed that barrier placement played an important role in connectivity. Not surprisingly, barriers located near the river mouth have the greatest impact on fish with diadromous life histories while those located near the center of the river network have the most impact on fish with potadromous life histories. The proposed index is conceptually simple and sufficiently flexible to deal with variations in river structure and biological communities. The index will enable researchers to account for connectivity in habitat studies and will also allow resource managers to characterize watersheds, assess cumulative impacts of multiple barriers and determine priorities for restoration

    Identifying tax implicit equivalence scales

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    This is a post-peer-review, pre-copyedit version of an article published in Journal of Economic Inequality. The final authenticated version is available online at: https://doi.org/10.1007/s10888-017-9354-x© 2017, Springer Science+Business Media New York. This paper describes a simple and tractable method for identifying equivalence scales that reflect the value judgements implicit in a tax and transfer system. The approach depends on two identifying assumptions and a functional description for transfer payments that can be estimated using common publicly available data sources. We use this approach to evaluate tax implicit equivalence scales for the tax-transfer systems of 12 European countries that applied in 2012. Cross-country averages for the tax implicit scales generate a surprising set of stylised results: at low incomes, each additional household member increases the tax implicit scale by approximately 0.5, relative to 1.0 for the first adult; at high incomes, the average tax implicit scales describe variation that is remarkably similar to the modified OECD scale. However, substantial cross-country variation underlies these average scales, suggesting important differences in value judgements implicit in the respective tax-transfer systems; differences that can otherwise be difficult to discern when systems are complex and opaque
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