Predictive accuracy of population viability analysis in conservation biology

Population viability analysis (PVA) is widely applied in conservation biology to predict extinction risks for threatened species and to compare alternative options for their management. It can also be used as a basis for listing species as endangered under World Conservation Union criteria. However, there is considerable scepticism regarding the predictive accuracy of PVA, mainly because of a lack of validation in real systems. Here we conducted a retrospective test of PVA based on 21 long-term ecological studies--the first comprehensive and replicated evaluation of the predictive powers of PVA. Parameters were estimated from the first half of each data set and the second half was used to evaluate the performance of the model. Contrary to recent criticisms, we found that PVA predictions were surprisingly accurate. The risk of population decline closely matched observed outcomes, there was no significant bias, and population size projections did not differ significantly from reality. Furthermore, the predictions of the five PVA software packages were highly concordant. We conclude that PVA is a valid and sufficiently accurate tool for categorizing and managing endangered species.     

Designing a Capability-Focused Strategic Management Model for a Turkish Public Hospital: Learning from Failure

This study aims to depict a failed strategic change initiative in a Turkish public hospital by means of an action research and it strives to explain critical factors underpinning the failure, thereby proposing how such factors should be tackled with for similar initiatives elsewhere. The study calls attention to the recent challenges ongoing in the environment of hospitals, which urge them to take on a more strategic focus. In this vein, we discredit accreditation based systems, which emphasize monitoring resources and propose a capability-focused strategic management model for hospitals. A hybrid action research protocol, which combines both traditional and participatory action research methodologies in its design, is employed to formulate and implement the model in a public hospital. The phases of the project and obstacles faced during these phases are discussed. The findings suggest that although the model offers significant potential for competitive success and better resource efficiency, path-dependent characteristics of the public sector governance in Turkey have impeded the adoption of the model in our case. Both macro-systemic characteristics related mainly to the Turkish national culture and management of public institutions and situation-specific characteristics, such as top management’s decision making orientation, professional norms and patronage relationships have blocked the way for the aspired transformation despite positive attitudes of and support from higher order public authorities and internal professional groups.     

Heterogeneous chemistry in the atmosphere of Mars

Hydrogen radicals are produced in the martian atmosphere by the photolysis of water vapour and subsequently initiate catalytic cycles that recycle carbon dioxide from its photolysis product carbon monoxide. These processes provide a qualitative explanation for the stability of the atmosphere of Mars, which contains 95 per cent carbon dioxide. Balancing carbon dioxide production and loss based on our current understanding of the gas-phase chemistry in the martian atmosphere has, however, proven to be difficult. Interactions between gaseous chemical species and ice cloud particles have been shown to be key factors in the loss of polar ozone observed in the Earth's stratosphere, and may significantly perturb the chemistry of the Earth's upper troposphere. Water-ice clouds are also commonly observed in the atmosphere of Mars and it has been suggested previously that heterogeneous chemistry could have an important impact on the composition of the martian atmosphere. Here we use a state-of-the-art general circulation model together with new observations of the martian ozone layer to show that model simulations that include chemical reactions occurring on ice clouds lead to much improved quantitative agreement with observed martian ozone levels in comparison with model simulations based on gas-phase chemistry alone. Ozone is readily destroyed by hydrogen radicals and is therefore a sensitive tracer of the chemistry that regulates the atmosphere of Mars. Our results suggest that heterogeneous chemistry on ice clouds plays an important role in controlling the stability and composition of the martian atmosphere.     

The Polycomb group protein EZH2 directly controls DNA methylation

The establishment and maintenance of epigenetic gene silencing is fundamental to cell determination and function. The essential epigenetic systems involved in heritable repression of gene activity are the Polycomb group (PcG) proteins and the DNA methylation systems. Here we show that the corresponding silencing pathways are mechanistically linked. We find that the PcG protein EZH2 (Enhancer of Zeste homolog 2) interacts-within the context of the Polycomb repressive complexes 2 and 3 (PRC2/3)-with DNA methyltransferases (DNMTs) and associates with DNMT activity in vivo. Chromatin immunoprecipitations indicate that binding of DNMTs to several EZH2-repressed genes depends on the presence of EZH2. Furthermore, we show by bisulphite genomic sequencing that EZH2 is required for DNA methylation of EZH2-target promoters. Our results suggest that EZH2 serves as a recruitment platform for DNA methyltransferases, thus highlighting a previously unrecognized direct connection between two key epigenetic repression systems.     

How Neanderthal molar teeth grew

Growth and development are both fundamental components of demographic structure and life history strategy. Together with information about developmental timing they ultimately contribute to a better understanding of Neanderthal extinction. Primate molar tooth development tracks the pace of life history evolution most closely, and tooth histology reveals a record of birth as well as the timing of crown and root growth. High-resolution micro-computed tomography now allows us to image complex structures and uncover subtle differences in adult tooth morphology that are determined early in embryonic development. Here we show that the timing of molar crown and root completion in Neanderthals matches those known for modern humans but that a more complex enamel-dentine junction morphology and a late peak in root extension rate sets them apart. Previous predictions about Neanderthal growth, based only on anterior tooth surfaces, were necessarily speculative. These data are the first on internal molar microstructure; they firmly place key Neanderthal life history variables within those known for modern humans.