Biology Reference
In-Depth Information
nus cyanocephalus
) and that they did not respond to the foot-thumping
alarm sounds of other animals. He concluded that relaxation of predator
recognition was due to reduced selection over the years in New Zealand.
Berger (1998) also noted reduced predator recognition in ungulates that
had lived in predator-free areas for 50-100 yr.
Beyond Adaptation to Habitat
A wide range of plant and animal studies show that evolutionary
responses to habitat conditions, some very rapid, often follow the intro-
duction of species to new geographical regions. These adjustments
include adaptation to new conditions of both the abiotic and biotic envi-
ronments. Changes in conditions of the physical habitat, release from con-
straints of gene flow in native regions, and escape from biotic enemies in
the native region all favor rapid evolutionary adjustments.
Adjustments of alien species to their new biotic environment, how-
ever, go far beyond the general response to the predation regime sug-
gested by the studies of Blossey and Nötzold (1995). In the next three
chapters, we shall examine adaptation by alien species to the new biotic
resources they encounter. Introduced herbivores, for example, usually
encounter a greatly altered range of potential food plants. In the next
chapter, we shall examine some of the evolutionary responses shown by
alien herbivores to this new array of potential foods.
