Naturalization of central European plants in North America: species traits, habitats, propagule pressure, residence time

Abstract

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.

Characteristics of Successful Alien Plants

“…van Kleunen et al (2007) showed for a comprehensive data set of 1036 species of Iridaceae native to southern Africa that international horticultural usage was more likely for species with a larger native range, a lower maximal altitude in southern Africa and a greater height. Similarly, Pysek et al (2014) found that Central European species with a greater height and bigger propagules were more likely to be used in cultivation both in their native range and in North America. Second, the sink-region approach (sensu Pysek et al 2004) tests how alien species, irrespective of whether they are invasive or not, deviate from native species in the introduced region.…”

Gap-filling a spatially explicit plant trait database: comparing imputation methods and different levels of environmental information

“…In MICE, parameters can be pooled across datasets to produce unbiased estimates and standard errors, providing a natural way to take into account the additional uncertainty introduced in the analysis by the presence of missing data, and to avoid circularity effects (van Buuren, 2012). However, ecological studies using multiple imputation approaches usually only apply the imputation step (Baraloto et al, 2010;Paine et al, 2011;Pyšek et al, 2015;Díaz et al, 2016) and do not take advantage of the multiple imputation framework to quantify the uncertainty resulting from the presence of missing data (but see Fisher et al, 2003).…”

“…While forest inventories have adopted statistical imputation methods for some time, as for example the kNN methods (Eskelson et al, 2009, and references therein), imputation methods have only recently started to be used in traitbased ecology (Baraloto et al, 2010;Pyšek et al, 2015).…”

How the Yellowhammer became a Kiwi: the history of an alien bird invasion revealed

“…Nevertheless, it is far from the truth that historical data on bird introductions are poor. Our paper demonstrates that the quantity and quality of historical information may be much higher than has been argued, which can potentially improve the precision of analyses based on it (Pyšek et al 2015). Rather, they are simply hard work to unearth.…”