2,268 research outputs found

    Stable pollination service in a generalist high Arctic community despite the warming climate

    Get PDF
    Insects provide key pollination services in most terrestrial biomes, but this service depends on a multistep interaction between insect and plant. An insect needs to visit a flower, receive pollen from the anthers, move to another conspecific flower, and finally deposit the pollen on a receptive stigma. Each of these steps may be affected by climate change, and focusing on only one of them (e.g., flower visitation) may miss important signals of change in service provision. In this study, we combine data on visitation, pollen transport, and single-visit pollen deposition to estimate functional outcomes in the high Arctic plant-pollinator network of Zackenberg, Northeast Greenland, a model system for global warming-associated impacts in pollination services. Over two decades of rapid climate warming, we sampled the network repeatedly: in 1996, 1997, 2010, 2011, and 2016. Although the flowering plant and insect communities and their interactions varied substantially between years, as expected based on highly variable Arctic weather, there was no detectable directional change in either the structure of flower-visitor networks or estimated pollen deposition. For flower-visitor networks compiled over a single week, species phenologies caused major within-year variation in network structure despite consistency across years. Weekly networks for the middle of the flowering season emerged as especially important because most pollination service can be expected to be provided by these large, highly nested networks. Our findings suggest that pollination ecosystem service in the high Arctic is remarkably resilient. This resilience may reflect the plasticity of Arctic biota as an adaptation to extreme and unpredictable weather. However, most pollination service was contributed by relatively few fly taxa (Diptera: Spilogona sanctipauli and Drymeia segnis [Muscidae] and species of Rhamphomyia [Empididae]). If these key pollinators are negatively affected by climate change, network structure and the pollination service that depends on it would be seriously compromised.Peer reviewe

    Stable pollination service in a generalist high Arctic community despite the warming climate

    Full text link
    Insects provide key pollination services in most terrestrial biomes, but this service depends on a multistep interaction between insect and plant. An insect needs to visit a flower, receive pollen from the anthers, move to another conspecific flower, and finally deposit the pollen on a receptive stigma. Each of these steps may be affected by climate change, and focusing on only one of them (e.g., flower visitation) may miss important signals of change in service provision. In this study, we combine data on visitation, pollen transport, and single-visit pollen deposition to estimate functional outcomes in the high Arctic plant-pollinator network of Zackenberg, Northeast Greenland, a model system for global warming–associated impacts in pollination services. Over two decades of rapid climate warming, we sampled the network repeatedly: in 1996, 1997, 2010, 2011, and 2016. Although the flowering plant and insect communities and their interactions varied substantially between years, as expected based on highly variable Arctic weather, there was no detectable directional change in either the structure of flower-visitor networks or estimated pollen deposition. For flower-visitor networks compiled over a single week, species phenologies caused major within-year variation in network structure despite consistency across years. Weekly networks for the middle of the flowering season emerged as especially important because most pollination service can be expected to be provided by these large, highly nested networks. Our findings suggest that pollination ecosystem service in the high Arctic is remarkably resilient. This resilience may reflect the plasticity of Arctic biota as an adaptation to extreme and unpredictable weather. However, most pollination service was contributed by relatively few fly taxa (Diptera: Spilogona sanctipauli and Drymeia segnis [Muscidae] and species of Rhamphomyia [Empididae]). If these key pollinators are negatively affected by climate change, network structure and the pollination service that depends on it would be seriously compromised

    Selection Criteria for Drug-Eluting Versus Bare-Metal Stents and the Impact of Routine Angiographic Follow-Up 2-Year Insights From the HORIZONS-AMI (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction) Trial

    Get PDF
    ObjectivesWe sought to identify patients with ST-segment elevation myocardial infarction most likely to benefit from drug-eluting stents (DES), and to evaluate the impact of routine angiographic follow-up on the apparent differences between stent types.BackgroundDES might have greatest utility in patients who would benefit most from their antirestenotic properties.MethodsWe randomly assigned 3,006 patients with ST-segment elevation myocardial infarction to paclitaxel-eluting stents (PES) or to bare-metal stents (BMS). Events were assessed at 12 months and 24 months, with a subset undergoing routine angiographic follow-up at 13 months. Using well-known risk factors for restenosis and target lesion revascularization (TLR), risk groups were formed to examine the absolute differences between PES and BMS.ResultsCompared with BMS, PES reduced TLR at 12 months from 7.4% to 4.5% (p = 0.003). Insulin-treated diabetes mellitus (hazard ratio: 3.12), reference vessel diameter ≤3.0 mm (hazard ratio: 2.89), and lesion length ≥30 mm (hazard ratio: 2.49) were independent predictors of 12-month TLR after BMS. In patients with 2 or 3 of these baseline risk factors, PES compared with BMS markedly reduced 12-month TLR (19.8% vs. 8.1%, p = 0.003). In patients with 1 of these risk factors, the 12-month rates of TLR were modestly reduced by PES (7.3% vs. 4.3%, p = 0.02). The 12-month TLR rates were low and similar for both stents in patients with 0 risk factors (3.3% vs. 3.2%, p = 0.93). Routine 13-month angiographic follow-up resulted in a marked increase in TLR procedures (more so with BMS) so that the absolute incremental benefit of PES compared with BMS doubled from 2.9% at 12 months to 6.0% at 24 months, a difference evident in all risk strata.ConclusionsPatients at high risk for TLR after BMS in ST-segment elevation myocardial infarction for whom DES are of greatest benefit may be identified. Conversely, DES may be of less clinical benefit for patients at lower risk for TLR after BMS. Routine angiographic follow-up increases the perceived clinical benefits of DES, and must be avoided to accurately estimate absolute treatment effects. (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction [HORIZONS-AMI]; NCT00433966
    corecore