1,101 research outputs found

    Linking Speciation to Extinction: Diversification Raises Contemporary Extinction Risk in Amphibians

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    Many of the traits associated with elevated rates of speciation, including niche specialization and having small and isolated populations, are similarly linked with an elevated risk of extinction. This suggests that rapidly speciating lineages may also be more extinction prone. Empirical tests of a speciation-extinction correlation are rare because assessing paleontological extinction rates is difficult. However, the modern biodiversity crisis allows us to observe patterns of extinction in real time, and if this hypothesis is true then we would expect young clades that have recently diversified to have high contemporary extinction risk. Here, we examine evolutionary patterns of modern extinction risk across over 300 genera within one of the most threatened vertebrate classes, the Amphibia. Consistent with predictions, rapidly diversifying amphibian clades also had a greater share of threatened species. Curiously, this pattern is not reflected in other tetrapod classes and may reflect a greater propensity to speciate through peripheral isolation in amphibians, which is partly supported by a negative correlation between diversification rate and mean geographic range size. This clustered threat in rapidly diversifying amphibian genera means that protecting a small number of species can achieve large gains in preserving amphibian phylogenetic diversity. Nonindependence between speciation and extinction rates has many consequences for patterns of biodiversity and how we may choose to conserve it

    The New Legal Puritanism of Catharine MacKinnon

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    Amphibian Species’ Traits, Evolutionary History, and Environment Predict Batrachochytrium Dendrobatidis Infection Patterns, but not Extinction Risk

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    The fungal pathogen Batrachochytrium dendrobatidis (B. dendrobatidis) has emerged as a major agent of amphibian extinction, requiring conservation intervention for many susceptible species. Identifying susceptible species is challenging, but many aspects of species biology are predicted to influence the evolution of host resistance, tolerance, or avoidance strategies towards disease. In turn, we may expect species exhibiting these distinct strategies to differ in their ability to survive epizootic disease outbreaks. Here, we test for phylogenetic and trait-based patterns of B. dendrobatidis infection risk and infection intensity among 302 amphibian species by compiling a global data set of B. dendrobatidis infection surveys across 95 sites. We then use best-fit models that associate traits, taxonomy and environment with B. dendrobatidis infection risk and intensity to predict host disease mitigation strategies (tolerance, resistance, avoidance) for 122 Neotropical amphibian species that experienced epizootic B. dendrobatidis outbreaks, and noted species persistence or extinction from these events. Aspects of amphibian species life history, habitat use and climatic niche were consistently linked to variation in B. dendrobatidis infection patterns across sites around the world. However, predicted B. dendrobatidis infection risk and intensity based on site environment and species traits did not reveal a consistent pattern between the predicted host disease mitigation strategy and extinction outcome. This suggests that either tolerant or resistant species may have no advantage in ameliorating disease during epizootic events, or that other factors drive the persistence of amphibian populations during chytridiomycosis outbreaks. These results suggest that using a trait-based approach may allow us to identify species with resistance or tolerance to endemic B. dendrobatidis infections, but that this approach may be insufficient to ultimately identify species at risk of extinction from epizootics

    Diffusion of published cost-utility analyses in the field of health policy and practice

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    OBJECTIVES: The diffusion of cost-utility analyses (CUAs) through the medical literature was examined, documenting visible patterns and determining how they correspond with expectations about the diffusion of process innovations. METHODS: This study used 539 CUAs from a registry. It includes data elements comprising year of publication, the research center in which the study was performed, the clinical area covered by the CUA, and the specific journal. Finally, each paper was assigned to a journal type that could be one of the three categories: health services research, general medicine, or clinical specialty. RESULTS: When the average number of publications is plotted against time, the plot reveals an S-shaped curve. It appears that, whereas CUAs initially were published more frequently in general medical or health services research journals, there was a clear increase in the diffusion of CUA into subspecialty journals over time. The concentration ratio for research centers as measured by the Herfindhal-Hirschman Index decreased over time. CONCLUSIONS: The spread of CUA through the medical literature follows patterns identified for the diffusion of other new technologies and processes. Future research should focus on what impact this spread has had on the practice of medicine and formulation of health policy

    Predictors of Comorbid Eating Disorders and Association with Other Obsessive-Compulsive Spectrum Disorders in Trichotillomania

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    Trichotillomania (TTM) and eating disorders (ED) share many phenomenological similarities, including ritualized compulsive behaviors. Given this, and that comorbid EDs may represent additional functional burden to hair pullers, we sought to identify factors that predict diagnosis of an ED in a TTM population. Subjects included 555 adult females (age range 18–65) with DSM-IV-TR TTM or chronic hair pullers recruited from multiple sites. 7.2% (N = 40) of our TTM subjects met criteria for an ED in their lifetime. In univariable regression analysis, obsessive-compulsive disorder (OCD), Yale-Brown Obsessive Compulsive Scale (Y-BOCS) worst-ever compulsion and total scores, certain obsessive-compulsive spectrum disorders, anxiety disorder, attention-deficit/hyperactivity disorder (ADHD), and substance disorder all met the pre-specified criteria for inclusion in the multivariable analysis. In the final multivariable model, diagnosis of OCD (OR: 5.68, 95% CI: 2.2–15.0) and diagnosis of an additional body-focused repetitive behavior disorder (BFRB) (OR: 2.69, 95% CI: 1.1–6.8) were both associated with increased risk of ED in TTM. Overall, our results provide further support of the relatedness between ED and TTM. This finding highlights the importance of assessing for comorbid OCD and additional BFRBs in those with TTM. Future research is needed to identify additional predictors of comorbid disorders and to better understand the complex relationships between BFRBs, OCD and EDs

    Evidence of Fragmenting Dust Particles from Near-Simultaneous Optical and Near-IR Photometry and Polarimetry of Comet 73P/Schwassmann-Wachmann 3

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    We report imaging polarimetry of segments B and C of the Jupiter-family Comet 73P/Schwassmann-Wachmann 3 in the I and H bandpasses at solar phase angles of approximately 35 and 85deg. The level of polarization was typical for active comets, but larger than expected for a Jupiter-family comet. The polarimetric color was slightly red (dP/dL = +1.2 +/- 0.4) at a phase angle of ~ 35deg and either neutral or slightly blue at a phase angle of ~ 85deg. Observations during the closest approach from 2006 May 11-13 achieved a resolution of 35 km at the nucleus. Both segments clearly depart from a 1/rho surface brightness for the first 50 - 200 km from the nucleus. Simulations of radiation driven dust dynamics can reproduce some of the observed coma morphology, but only with a wide distribution of initial dust velocities (at least a factor of 10) for a given grain radius. Grain aggregate breakup and fragmentation are able to reproduce the observed profile perpendicular to the Sun-Comet axis, but fit the observations less well along this axis (into the tail). The required fragmentation is significant, with a reduction in the mean grain aggregate size by about a factor of 10. A combination of the two processes could possibly explain the surface brightness profile of the comet.Comment: 40 pages including 11 figure
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