Abstract
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The invasion of many habitats by exotic shrubs and trees has been an important factor
causing changes in Australian native vegetation through declines in species richness,
changes to community composition and reducing ecosystem function (Lindsay and
French 2004; Gosper eta!. 2006; Mason and French 2007; Gooden et at. 2009). Costs
of management have been high (Sinden et a!. 2004) and research into management
options extensive. Whilst management-oriented research places Australia at the leading
edge ofthe field (Briese 2004), this has been at the expense of research testing hypotheses
about mechanisms of invasion in Australia.
Information on the novel distribution, population dynamics and ecology of the majority
of invasive species is largely unknown. Ten species of exotic woody shrub or small tree are
among the 20 Weeds ofNational Significance (WoNS) classified by the Australian Federal
Government, reflecting their extensive current and/or projected impact on native and
agricultural communities. Funding for weed research is largely focused on these WoNS
but directed specifically to the development of successful management options. Very little
is directed to understanding invasion or impacts. Additionally, a further 100 shrubs and
trees (and more herbs, grasses and vines) are known as significant environmental weeds
and described in a range ofland management resources (e.g. http://www.weeds.org.au).
Almost nothing is understood about these species. Many invasive shrubs and trees have
invaded from horticultural stock, and the species may differ from native stock (e.g. Lantana
camara L., lantana, Figure 13.1) causing difficulties in both management and in understanding
ecological consequences.