Using structural equation modelling to test the passenger, driver and opportunist concepts in a Poa pratensis invasion. Issue 3 (7th September 2012)

• Record Type: Journal Article
• Authors: White, Shannon R.; Tannas, Steven; Bao, Tan; Bennett, Jonathan A.; Bork, Edward W.; Cahill, James F.
• Is Part Of: Oikos. Volume 122:Issue 3(2013)
• Page Start: 377
• Page End: 384
• Publication Date: 2012-09-07
• Subjects: Ecology -- Periodicals; 570
• DOI: 10.1111/j.1600-0706.2012.20951.x
• Languages: English
• ISSNs: 0030-1299

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The passenger, driver, and opportunist models are conceptual models of the invasion process used to describe alternative invasion scenarios. In the passenger model, both the invasive species and native community respond independently to environmental changes. In the driver model, changes to the native community are driven by the invasive species, while in the opportunist model invasion occurs in response to changes in the native community. In any given invasion scenario, however, it is possible that the relationships between the invasive, the native community, and the environment correspond to some combination of these invasion models acting simultaneously. We study invasion by <italic>Poa pratensis</italic> in a grassland in Alberta, Canada. <italic>Poa pratensis</italic> is a non‐native plant implicated with loss of plant diversity in the region. In a three year field experiment, we manipulate the environment though defoliation, water addition, and nitrogen addition, and measure responses of <italic>P. pratensis</italic> cover, and cover and richness of the native community. We use structural equation modelling to describe the relationships between the invasive, the native community, and the environmental changes, and then interpret these relationships using the three invasion models. We found that <italic>P. pratensis</italic> predominantly invaded via the driver model, with subsequent reductions in native plant cover, but not in species richness. Positive effects of the environmental changes on <italic>P. pratensis</italic> also aided its ability to drive native cover. As well, we found some involvement of the opportunist model, through a negative relationship between the native community and the invasive. As invasion mainly proceeded via the driver model, management actions to limit invasion should focus on efforts to control abundance of <italic>P. pratensis</italic> itself.</p> </abstract>