Climate refugia can serve as a remnant habitat or stepping stones for species dispersal under climate warming.The largest freshwater lake by surface area,Lake Superior,USA and Canada,serves as a model system for under...Climate refugia can serve as a remnant habitat or stepping stones for species dispersal under climate warming.The largest freshwater lake by surface area,Lake Superior,USA and Canada,serves as a model system for understanding cooling-mediated local refugia,as its cool water temperatures and wave action have maintained shoreline habitats suitable for southern disjunct populations of arctic-alpine plants since deglaciation.Here,we seek to explain spatial patterns and environmental drivers of arctic-alpine plant refugia along Lake Superior’s shores,and assess future risk to refugia under moderate(+3.5℃)and warmest(+5.7℃)climate warming scenarios.First,we examined how the interactive effects of summer surface water temperatures and wind affected onshore temperatures,resulting in areas of cooler refugia.Second,we developed an ecological niche model for the presence of disjunct arctic-alpine refugia(pooling 1253 occurrences from 58 species)along the lake’s shoreline.Third,we fit species distribution models for 20 of the most common arctic-alpine disjunct species and predicted presence to identify refugia hotspots.Finally,we used the two climate warming scenarios to predict changes in the presence of refugia and disjunct hotspots.Bedrock type,elevation above water,inland distance,July land surface temperature from MODIS/Terra satellite and near-shore depth of water were the best predictors of disjunct occurrences.Overall,we predicted 2236 km of the shoreline(51%)as disjunct refugia habitat for at least one species under current conditions,but this was reduced to 20% and 7% with moderate(894 km)and warmest(313 km)climate change projections.展开更多
Trend test in dose-response has been a central problem in medicine. This paper treats the problem of comparing umbrella pattern treatment effects. Under an ordered m × r × k table, this article considers tes...Trend test in dose-response has been a central problem in medicine. This paper treats the problem of comparing umbrella pattern treatment effects. Under an ordered m × r × k table, this article considers testing the hypothesis that all multinomial populations are conditional independence against the alternative that they are in an umbrella trend. For this hypothesis test problem, this article introduces a model-free test method by using likelihood ratio test statistic and gives the asymptotic distribution of the test statistic. Simulation study is conducted to compare the empirical power per- formed via the proposed method and others. Finally, two real data are studied to illustrate the validity of the proposed method.展开更多
基金supported by the Natural Sciences and Engineering Research Council of Canada(RGPIN-2019-06040).
文摘Climate refugia can serve as a remnant habitat or stepping stones for species dispersal under climate warming.The largest freshwater lake by surface area,Lake Superior,USA and Canada,serves as a model system for understanding cooling-mediated local refugia,as its cool water temperatures and wave action have maintained shoreline habitats suitable for southern disjunct populations of arctic-alpine plants since deglaciation.Here,we seek to explain spatial patterns and environmental drivers of arctic-alpine plant refugia along Lake Superior’s shores,and assess future risk to refugia under moderate(+3.5℃)and warmest(+5.7℃)climate warming scenarios.First,we examined how the interactive effects of summer surface water temperatures and wind affected onshore temperatures,resulting in areas of cooler refugia.Second,we developed an ecological niche model for the presence of disjunct arctic-alpine refugia(pooling 1253 occurrences from 58 species)along the lake’s shoreline.Third,we fit species distribution models for 20 of the most common arctic-alpine disjunct species and predicted presence to identify refugia hotspots.Finally,we used the two climate warming scenarios to predict changes in the presence of refugia and disjunct hotspots.Bedrock type,elevation above water,inland distance,July land surface temperature from MODIS/Terra satellite and near-shore depth of water were the best predictors of disjunct occurrences.Overall,we predicted 2236 km of the shoreline(51%)as disjunct refugia habitat for at least one species under current conditions,but this was reduced to 20% and 7% with moderate(894 km)and warmest(313 km)climate change projections.
基金supported by the National Natural Science Foundation of China under Grant No.10771163
文摘Trend test in dose-response has been a central problem in medicine. This paper treats the problem of comparing umbrella pattern treatment effects. Under an ordered m × r × k table, this article considers testing the hypothesis that all multinomial populations are conditional independence against the alternative that they are in an umbrella trend. For this hypothesis test problem, this article introduces a model-free test method by using likelihood ratio test statistic and gives the asymptotic distribution of the test statistic. Simulation study is conducted to compare the empirical power per- formed via the proposed method and others. Finally, two real data are studied to illustrate the validity of the proposed method.
