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Figure 1. The relationship between invasion and species richness. (A) Total species richness as a func-
tion of the proportion exotic plant cover (Spearman rank-sum correlation R = -0.42; P = 0.003) (B)
Exotic species richness as a function of native species richness (Spearman rank-sum correlation
R = 0.40; P = 0.005). Data were collected as percent cover in 1 m 2 plots as part of the BSS.
the local community. Changes in diversity in this context are a consequence of
invasion. Conservationists largely present this view as justification for the con-
trol and regulation of exotic plant species [13, 14].
Unfortunately, most studies have only addressed invasions from the cause or
consequence perspective, leaving the true nature of the relationship unresolved.
Currently, it is unknown whether the relationship between exotic plant invasion
and diversity is caused by the local displacement of species by plant invaders,
differential invasibilities of areas of varying diversity, or some combination of
both. In this chapter, we specifically identify limitations of the current perspec-
tive on invasion and propose a conceptual framework from which to address the
nature of the relationship between diversity and invasion. The framework aims
to abstract the components of this relationship to allow generalization across
systems and invaders, thereby enhancing ecological understanding of the caus-
es and consequences of invasion. Several case studies are provided to illustrate
the necessity of separating these two disparate perspectives of plant invasions.
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