Abstract
In order to combat the growing problems associated with biological invasions, many researchers have focused on identifying which communities are most vulnerable to invasion by exotic species. However, once established, invasive species can significantly change the composition of the communities that they invade. The first step to disentangling the direction of causality is to discern whether a relationship with other vegetation exists at all. Carduus nutans and C. acanthoides are similar invasive thistles, which have caused substantial economic damage worldwide. We assessed the associations between the thistles and the standing flora in four sites in central Pennsylvania in which they co-occur. After sampling nearly 2000 plots of 1 m(2), we used partial Mantel tests to assess the differences in vegetation between thistle and non-thistle plots after accounting for location, and non-metric multidimensional scaling to visualize differences among plots and sites. We found significant differences in community composition in plots with and without Carduus thistles. The non-native species Sisymbrium officinale and Coronilla varia were consistently associated with the presence of Carduus thistles. Several species were associated with areas that were free of Carduus thistles, including an important non-native pasture species (Trifolium repens). We found no evidence for differences in composition between plots with C. nutans versus C. acanthoides, suggesting that they have similar associations with the vegetation community. We conclude that even at the within-field scale, areas invaded by Carduus thistles have different vegetation associations than uninvaded areas, allowing us to target future research about the role of vegetation structure in resisting and responding to invasion.
Highlights
In order to combat the growing problems associated with biological invasions, there has been a focus on identifying which communities are most vulnerable to invasion by exotic species (Baker 1974; Pysek et al 1995; Rejmanek and Richardson 1996; Theoharides and Dukes 2007; Van Kleunen et al 2010), some have criticized this approach (Thompson and Davis 2011)
We focused on the few areas of co-occurrence of both species, which led to different sized survey areas in each site
We clearly showed differences in the plant community associations in areas with and without these two species
Summary
In order to combat the growing problems associated with biological invasions, there has been a focus on identifying which communities are most vulnerable to invasion by exotic species (Baker 1974; Pysek et al 1995; Rejmanek and Richardson 1996; Theoharides and Dukes 2007; Van Kleunen et al 2010), some have criticized this approach (Thompson and Davis 2011). Invasive species can affect the communities that they invade.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
