Reconciling Deep Calibration and Demographic History: Bayesian Inference of Post Glacial Colonization Patterns in Carcinus aestuarii (Nardo, 1847) and C. maenas (Linnaeus, 1758)

A precise inference of past demographic histories including dating of demographic events using Bayesian methods can only be achieved with the use of appropriate molecular rates and evolutionary models. Using a set of 596 mitochondrial cytochrome c oxidase I (COI) sequences of two sister species of European green crabs of the genus Carcinus (C. maenas and C. aestuarii), our study shows how chronologies of past evolutionary events change significantly with the application of revised molecular rates that incorporate biogeographic events for calibration and appropriate demographic priors. A clear signal of demographic expansion was found for both species, dated between 10,000 and 20,000 years ago, which places the expansions events in a time frame following the Last Glacial Maximum (LGM). In the case of C. aestuarii, a population expansion was only inferred for the Adriatic-Ionian, suggestive of a colonization event following the flooding of the Adriatic Sea (18,000 years ago). For C. maenas, the demographic expansion inferred for the continental populations of West and North Europe might result from a northward recolonization from a southern refugium when the ice sheet retreated after the LGM. Collectively, our results highlight the importance of using adequate calibrations and demographic priors in order to avoid considerable overestimates of evolutionary time scales

Capturing coastal morphological change within regional integrated assessment: an outcome-driven fuzzy logic approach

Climate change will have pervasive effects on the world’s coasts, but at broad scalesthese changes have typically proven difficult to analyse in a systematic manner. Thispaper explores an outcome-driven deductive methodology for geomorphologicalanalysis that structures current knowledge and understanding using fuzzy logicconcepts. Building on recent large-scale coastal investigations and with reference to acase study of the East Anglian coast U.K, the methodology defines the active coastalsystem using a flexible generic classification and integrates expert opinion, using thenotion of possibility, as a basis for the assessment of potential futuregeomorphological response to changes in sea level and sediment supply.The proposed methodology produces a robust qualitative structure for assessment andforecasting of coastal geomorphology. Preliminary results for the East Anglian coastsuggest that shoreline management is already having, and will continue to be, asignificant influence on coastal evolution irrespective of the rate of sea-level rise.Therefore, significant potential exists to guide future coastal evolution towardspreferred outcomes by using such methods as a component of adaptive shorelinemanagement. This methodology could be applied to a wide range of problems both ingeomorphology and other subject

Capturing geomorphological change in the coastal simulator

The Tyndall Centre’s Regional Coastal Simulator aims to provide an integrated perspective on the impact of climate change on the coastal zone at the regional (e.g. East Anglian) scale, including taking account of the choices available for shoreline management. Coastal geomorphology is fundamental to both prediction and understanding of the ecological and social implications of climate change but the application of process-based modelling at broad-scales remain relatively limited due to the complexity of the systems involved. This project aimed to explore a more deductive methodology for geomorphologicalanalysis at the regional scale incorporating expert knowledge and understanding. This involved the development of a modifiable generic classification capable of including the impacts of different management scenarios - by definition of the active coastal system - and the integration of expert opinion, using the concepts of possibility and probability within fuzzy logic, on the potential future response of elements within the classification to changes in sea level. Applied to the East Anglian coast, this approach has identified broad patterns of shoreline retreat accompanied by narrowing of beaches and barriers in response to increases in the rate of sea-level rise and/or the proportion of defended coast. Hence, shoreline management has a profound effect on future coastal evolution, highlighting the significant potential for guiding future coastal evolution towards preferred outcomes. While this approach produces a robust qualitative assessment of change, further work is required to investigate suitable techniques for translating outcomes in to a computational form suitable for the prototype Coastal Simulator which maintain the probabilistic aspects of the approach

Capturing coastal geomorphological change within regional integrated assessment: an outcome-driven fuzzy logic approach

Climate change will have pervasive effects on the world's coasts, but at broad scales these changes have typically proven difficult to analyse in a systematic manner. This paper explores an outcome-driven deductive methodology for geomorphological analysis that recognises the nonlinearity of coastal morphology and organises current knowledge and understanding using fuzzy logic concepts. Building on recent large-scale coastal investigations and with reference to a case study of the East Anglian coast, U.K., the methodology defines the active coastal system using a flexible generic classification and integrates expert opinion, using the notion of possibility, as a basis for the assessment of potential future geomorphological response to changes in sea level and sediment supply.Preliminary results for the East Anglian coast suggest that the constraining of the active coastal system by sea defences is already having, and will continue to be, a significant influence on coastal evolution irrespective of the rate of sea-level rise. Therefore, significant potential exists to guide future coastal evolution toward preferred outcomes by using this approach as a component of adaptive shoreline management. This methodology could be applied to a wide range of problems both in geomorphology and other subjects

The implications of cohesive shore platform erosion for coastal management.

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