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Chapel Hill, NC, United States

Stohlgren T.J.,U.S. Geological Survey | Pysek P.,Academy of Sciences of the Czech Republic | Pysek P.,Charles University | Kartesz J.,Biota of North America Program | And 12 more authors.
Biological Invasions | Year: 2011

Estimates of the level of invasion for a region are traditionally based on relative numbers of native and alien species. However, alien species differ dramatically in the size of their invasive ranges. Here we present the first study to quantify the level of invasion for several regions of the world in terms of the most widely distributed plant species (natives vs. aliens). Aliens accounted for 51.3% of the 120 most widely distributed plant species in North America, 43.3% in New South Wales (Australia), 34.2% in Chile, 29.7% in Argentina, and 22.5% in the Republic of South Africa. However, Europe had only 1% of alien species among the most widespread species of the flora. Across regions, alien species relative to native species were either as well-distributed (10 comparisons) or more widely distributed (5 comparisons). These striking patterns highlight the profound contribution that widespread invasive alien plants make to floristic dominance patterns across different regions. Many of the most widespread species are alien plants, and, in particular, Europe and Asia appear as major contributors to the homogenization of the floras in the Americas. We recommend that spatial extent of invasion should be explicitly incorporated in assessments of invasibility, globalization, and risk assessments. © 2011 Springer Science+Business Media B.V.


Kalusova V.,Masaryk University | Chytry M.,Masaryk University | Kartesz J.T.,Biota of North America Program | Nishino M.,Biota of North America Program | And 2 more authors.
Diversity and Distributions | Year: 2013

Aim: The percentage of alien species found in a given habitat depends on the habitat vulnerability to invasion (invasibility) and the number of species introduced (propagule pressure). However, the global pool of alien species suited to a given habitat also varies. Here, we identify donor habitats of invasive alien plant species originating from Europe, examine the match between habitats they occupy in Europe and recipient areas and test whether donor habitats of invasive plants tend to be vulnerable or resistant to invasions. Location: Europe (source area), North America and the World (recipient areas). Methods: Native European vascular plants invasive in North America and other parts of the World were identified for 35 European natural habitats. Percentages of species invasive outside Europe, of the total number of native species occurring in each European habitat, were used to compare these habitats as donors for invasion. Habitat preferences of European species in their recipient areas were compared with those in Europe. Results: European alluvial forests, alder carrs and coastal sand-dunes harbour the highest percentages of native species that are invasive outside Europe. Outside their native range, European species tend to invade habitats that are similar to their donor habitats in Europe, but species of alluvial and coastal habitats also frequently invade other habitats. European habitats that are important donors of invasive species globally experience the highest levels of invasion by alien species from other regions; this relationship was, however, not confirmed for invasions to North America if considered separately. Main conclusions: Some European habitats are more important donors of invasive plants than others. Therefore, the level of invasion of different habitats is affected also by the differences in the number of invasive species provided by various donor habitats. At a global scale, more important donor habitats are also likely to be more invaded. © 2012 Blackwell Publishing Ltd.


Jarnevich C.S.,Fort Collins Science Center | Holcombe T.R.,Fort Collins Science Center | Barnett D.T.,Colorado State University | Stohlgren T.J.,Fort Collins Science Center | Kartesz J.T.,Biota of North America Program
Invasive Plant Science and Management | Year: 2010

The number of invasive exotic plant species establishing in the United States is continuing to rise. When prevention of exotic species from entering into a country fails at the national level and the species establishes, reproduces, spreads, and becomes invasive, the most successful action at a local level is early detection followed by eradication. We have developed a simple geographic information system (GIS) analysis for developing watch lists for early detection of invasive exotic plants that relies upon currently available species distribution data coupled with environmental data to aid in describing coarse-scale potential distributions. This GIS analysis tool develops environmental envelopes for species based upon the known distribution of a species thought to be invasive and represents the first approximation of its potential habitat while the necessary data are collected to perform more in-depth analyses. To validate this method we looked at a time series of species distributions for 66 species in Pacific Northwest and northern Rocky Mountain counties. The time series analysis presented here did select counties that the invasive exotic weeds invaded in subsequent years, showing that this technique could be useful in developing watch lists for the spread of particular exotic species. We applied this same habitat-matching model based upon bioclimatic envelopes to 100 invasive exotics with various levels of known distributions within continental U.S. counties. For species with climatically limited distributions, county watch lists describe county-specific vulnerability to invasion. Species with matching habitats in a county would be added to that county's list. These watch lists can influence management decisions for early warning, control prioritization, and targeted research to determine specific locations within vulnerable counties. This tool provides useful information for rapid assessment of the potential distribution based upon climate envelopes of current distributions for new invasive exotic species. © 2010 Weed Science Society of America.


Pysek P.,Academy of Sciences of the Czech Republic | Pysek P.,Charles University | Pysek P.,Stellenbosch University | Manceur A.M.,Helmholtz Center for Environmental Research | And 22 more authors.
Ecology | Year: 2015

The factors that promote invasive behavior in introduced plant species occur across many scales of biological and ecological organization. Factors that act at relatively small scales, for example, the evolution of biological traits associated with invasiveness, scale up to shape species distributions among different climates and habitats, as well as other characteristics linked to invasion, such as attractiveness for cultivation (and by extension propagule pressure). To identify drivers of invasion it is therefore necessary to disentangle the contribution of multiple factors that are interdependent. To this end, we formulated a conceptual model describing the process of invasion of central European species into North America based on a sequence of ''drivers.'' We then used confirmatory path analysis to test whether the conceptual model is supported by a statistical model inferred from a comprehensive database containing 466 species. The path analysis revealed that naturalization of central European plants in North America, in terms of the number of North American regions invaded, most strongly depends on residence time in the invaded range and the number of habitats occupied by species in their native range. In addition to the confirmatory path analysis, we identified the effects of various biological traits on several important drivers of the conceptualized invasion process. The data supported a model that included indirect effects of biological traits on invasion via their effect on the number of native range habitats occupied and cultivation in the native range. For example, persistent seed banks and longer flowering periods are positively correlated with number of native habitats, while a stress-tolerant life strategy is negatively correlated with native range cultivation. However, the importance of the biological traits is nearly an order of magnitude less than that of the larger scale drivers and highly dependent on the invasion stage (traits were associated only with native range drivers). This suggests that future research should explicitly link biological traits to the different stages of invasion, and that a failure to consider residence time or characteristics of the native range may seriously overestimate the role of biological traits, which, in turn, may result in spurious predictions of plant invasiveness. © 2015 by the Ecological Society of America.

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