Using structural equation modelling to test the passenger, driver and opportunist concepts in a Poa pratensis invasion

Abstract

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 Poa pratensis in a grassland in Alberta, Canada. Poa pratensis 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 P. pratensis 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 P. pratensis 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 P. pratensis 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 P. pratensis itself.

Does disturbance enhance the competitive effect of the invasive Solidago canadensis on the performance of two native grasses?

“…In contrast, according to the 'passenger' model, the invasive species has the ability to capitalize on disturbance, thus weak biotic interaction exists between invasive and native species without the presence of disturbance (Didham et al 2005). However, the interactions of drivers are much more complex, and these models should be considered as extremes of a continuum, which incorporates the combined effect of the factors acting in concert (Didham et al 2005;Chabrerie et al 2007;White et al 2013). Therefore, the 'passenger'/'driver' model has been expanded to include an intermediate 'backseat driver' model, where habitat disturbances and invasion act synergistically (Bauer 2012).…”

Patterns of phylogenetic diversity are linked to invasion impacts, not invasion resistance, in a native grassland

“…However, many characteristics proposed to increase invasion resistance within communities also change as a consequence of invasion; invasive species can be passengers or drivers of community change (MacDougall & Turkington ; White et al. ). For example, higher species diversity often reduces the likelihood of successful invasion (Levine et al.…”

Isolating the role of soil resources, defoliation, and interspecific competition on early establishment of the late successional bunchgrassFestuca campestris

“…Previous work suggests that P. pratensis , a fast growing perennial, acts as a driver of environmental change because it is adapted to the rapid capture and use of nutrients, and also benefits from increases in soil nitrogen (N) at the expense of slower growing species (White et al ). As a result, disturbed environments with high available N (Huenneke et al ; Lake & Leishman ; Hawkes et al ) may provide species such as P. pratensis that thrive under high N (Wilson & Tilman ) with a competitive advantage (Alpert et al ).…”