Biology Reference
In-Depth Information
Part II.
Processes of Evolutionary
Change and Adaptation
In this series of chapters, we examine some of the major mechanisms of
evolutionary change and how they relate to adaptation of alien species to
the new physical and biotic conditions they encounter.
Chapter 5 considers the increased frequency of hybridization that
results when closely related forms, whether they be different alien forms
or alien forms and related natives, are suddenly brought together. Some of
the most remarkable examples of the origin of invasive taxa can be traced
to hybridization and subsequent reorganization of the hybrid genomes.
Hybridization also holds the potential for the escape of transgenes from
genetically engineered plants, animals, and microorganisms to wild forms,
many of which are already problem aliens in various world regions. The
evolutionary consequences of acquisition of transgenes by wild plants,
animals, and microorganisms are of great current concern and will be
examined chapter 6.
The potential for invasion and adaptation to new ecological systems
depends on the evolutionary adaptability of aliens to the biotic and abi-
otic conditions encountered. Success depends on the ability to flourish in
the new biotic environment. In chapter 7, we shall examine factors that
determine the degree of resistance of biotic communities to invasion by
aliens and the factors that enable aliens to overcome such resistance. In
chapter 8, we consider patterns of evolutionary adaptation to these new
physical and biotic conditions. As we shall see, adaptive breakthroughs
often appear to be responsible for the sudden explosive change of alien
species from forms with only minor impacts to highly invasive forms with
serious impacts.
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