Both the success and the consequences of invasion by an exotic are determined by the
interaction between the invader and the host community. In this paper we couple a study
of resident plant diversity with the results of a demographic study on invading Cytisus
scoparius (Scotch or Scot’s broom) populations at five sites, to ask questions about the
relationship between invisibility and community characteristics. Population growth rate
of the invader was positively (not negatively) correlated with species richness, failing to
support the theory of biotic resistance. Population growth rate was negatively correlated
with the proportion of total cover occupied by the other exotic species, suggesting that
competition from previous aggressive invaders might play a role in reducing the success
of an actively expanding population.
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