34 research outputs found

    Conserved ancestral tropical niche but different continental histories explain the latitudinal diversity gradient in brush-footed butterflies.

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    The global increase in species richness toward the tropics across continents and taxonomic groups, referred to as the latitudinal diversity gradient, stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluate several of these hypotheses to explain spatial diversity patterns in a butterfly family, the Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal, and also the extent to which these processes differ among regions at the same latitude. We generate a time-calibrated phylogeny containing 2,866 nymphalid species (~45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the latitudinal diversity gradient among regions because temporal diversification dynamics differ greatly across longitude. The Neotropical diversity results from low extinction rates, not high speciation rates, and biotic interchanges with other regions are rare. Southeast Asia is also characterized by a low speciation rate but, unlike the Neotropics, is the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, combined with tropical niche conservatism, played a major role in generating the modern latitudinal diversity gradient of nymphalid butterflies

    New appraisal values of travel time saving and reliability in Great Britain

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    © 2017, The Author(s). This paper provides an overview of the study ‘Provision of market research for value of time savings and reliability’ undertaken by the Arup/ITS Leeds/Accent consortium for the UK Department for Transport (DfT). The paper summarises recommendations for revised national average values of in-vehicle travel time savings, reliability and time-related quality (e.g. crowding and congestion), which were developed using willingness-to-pay (WTP) methods, for a range of modes, and covering both business and non-work travel purposes. The paper examines variation in these values by characteristics of the traveller and trip, and offers insights into the uncertainties around the values, especially through the calculation of confidence intervals. With regards to non-work, our recommendations entail an increase of around 50% in values for commute, but a reduction of around 25% for other non-work—relative to previous DfT ‘WebTAG’ guidance. With regards to business, our recommendations are based on WTP, and thus represent a methodological shift away from the cost saving approach (CSA) traditionally used in WebTAG. These WTP-based business values show marked variation by distance; for trips of less than 20miles, values are around 75% lower than previous WebTAG values; for trips of around 100miles, WTP-based values are comparable to previous WebTAG; and for longer trips still, WTP-based values exceed those previously in WebTAG

    Longitudinal realist evaluation of the dementia PersonAlised care team (D-PACT) intervention: protocol

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    Background Different dementia support roles exist but evidence is lacking on which aspects are best, for whom and in what circumstance, and on their associated costs and benefits. Phase 1 of the Dementia PersonAlised Care Team programme (D-PACT), developed a post-diagnostic primary care-based intervention for people with dementia and their carers and assessed the feasibility of a trial. AimPhase 2 of the programme aims to 1) refine our programme theory on how, when and for whom the intervention works and 2) evaluate its value and impact. Design & setting A realist longitudinal mixed-methods evaluation will be conducted in urban, rural, and coastal areas across Southwest and Northwest England where low-income groups or ethnic minorities (eg, South Asian) are represented. Design was informed by patient, public and professional stakeholder input and Phase one findings. Method High volume qualitative and quantitative data will be collected longitudinally from people with dementia, carers and practitioners. Analyses will comprise: 1) realist longitudinal case studies; 2) conversation analysis of recorded interactions; 3) statistical analyses of outcome and experience questionnaires; 4 a) health economic analysis examining costs of delivery; 4b) realist economic analysis of high-cost events and ‘near misses’. All findings will be synthesised using a joint display table, evidence appraisal tool, triangulation and stakeholder co-analysis. Conclusion Our realist evaluation will describe how, why and for whom the intervention leads (or not) to change over time; it also demonstrates how a non-randomised design can be more appropriate for complex interventions with similar questions or populations
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