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Understanding species distributions remains central to research in ecology and biogeography. Emphasis is placed on the spatial presence/absence of plants as related to underlying environmental factors; however, distributions result from both abiotic factors and adaptations to the abiotic environment. We analyzed poison ivy (Toxicodendron radicans (L.) Kuntze), which has high intraspecies variability in the plant functional trait of growth habit, to assess implications of plant strategies for spatial distributions. Our objectives were to: 1) determine whether anthropogenic habitats are statistically overrepresented in poison ivy incidence and growth habits (shrub, climbing liana, crawling liana), and 2) model biophysical parameters that constitute preferred poison ivy habitat and the three growth habits. We collected poison ivy field data along a trail-transect with corresponding geospatially indexed parameters, subsequently analyzed using Bayesian spatial modeling. Model results revealed poison ivy preference for human-modified habitat; Developed and Planted/Cultivated land use categories showed the largest marginal posterior probabilities for crawling and climbing lianas. Increasing temperature and elevation preferentially benefit the climbing growth habit. Our results suggest that variability in functional traits may impact species geographic distributions by expanding niche breadth. Incorporation of functional traits may thus advance predictive niche models of species distributions. [ABSTRACT FROM AUTHOR]

The potential impact of invasive forest pathogens on alpine treeline dynamics has not previously been considered. Whitebark pine (Pinus albicaulis), a foundation and keystone species of subalpine forests and major component of alpine treeline in the northern Rocky Mountains of the United States and southern Canada, is infected nearly rangewide by the exotic pathogen Cronartium ribicola, which causes white pine blister rust. A major component of treeline in the northern Rocky Mountains, whitebark pine initiates tree islands on the eastern slope in northwestern Montana more than any other conifer species. Blister rust infects whitebark pine throughout the region, and both infection and mortality are already evident at treeline. We discuss the cascading ecological effects of the toss of treeline whitebark pine and expected changes in landscape vegetation patterns. Potential implications of the loss of whitebark pine for northwestern Montana treelines are examined in the context of climate change within a conceptual model. We speculate that exotic pathogens could potentially confound predictions of treeline responses to global warming in many geographic regions. [ABSTRACT FROM AUTHOR]