Biology Reference
In-Depth Information
success of new invaders (Richardson et al. 2000).The introduction of pol-
linator insects, for example, has favored the success of many plants that are
native to areas where these pollinators are native. Seed dispersal interac-
tions between alien plants and alien or native animals also favor the suc-
cess of both alien plants and alien animals in many cases.The presence of
a wide variety of alien microorganisms, plants, and animals now appears
to be facilitating the establishment of still other alien species.
New Habitats Mean New Evolutionary Pressures
Alien species are successful because they encounter not only favorable
conditions of the physical habitat, available resources, and mutualists, but
also because they have often escaped biotic limitations that existed in their
native region. Nevertheless, all aspects of their new environments are dif-
ferent from their native region to some degree.Thus, conditions favorable
to population growth combine with altered pressures of natural selection,
both biotic and abiotic. For many species, the result is rapid evolutionary
adaptation to the new conditions.We shall examine the evidence for such
adaptation to new habitat conditions in the next chapter.
