Biology Reference
In-Depth Information
Part IV.
Global Evolutionary Consequences
of Alien Invasions
The worldwide introduction of species to new geographical areas is influ-
encing global biodiversity in a number of major ways. Native floras and
faunas are being altered permanently by the massive introduction of alien
species, so much so that invasion biologists speak of the result as “biotic
homogenization.” Evolutionary interactions of alien and native species are
permanently altering these member species, as well as the communities
they form.
Introduced species are one of the main causes of increase in rates of
extirpation and extinction of native species, especially in insular environ-
ments such as oceanic islands and freshwater lakes and streams. In chapter
16, we shall examine the kinds of alien impacts that cause extirpations and
extinctions. The deliberate introduction of alien species for biological
control represents a special issue in alien biology. In chapter 17, we shall
examine the controversy relating to the possible role of deliberately intro-
duced biocontrol species in extirpation and extinction.
On the other hand, diversity in many ecological systems is being
increased by the addition of new species. In chapter 18, we shall examine
how the negative impacts of some of these new species are mitigated and
how they become integrated into these systems. In addition, interactions
of aliens and natives may result in the origin of new species, thus offset-
ting to a degree the impacts of aliens as agents of extinction. In chapter
19, we shall consider the role of alien introductions in increasing the rate
of speciation.
Finally, in chapter 20, we shall examine how alien introductions inter-
act with other aspects of global change, particularly climatic change, to
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