3 Animals as individuals
In order to manage a population we need to know something about the character-
istics of its members. We seek knowledge of their morphological and physiological
adaptations to environment, their behavior, particularly with respect to dispersal, repro-
duction, and use of habitat, and the genetic variability among them.
In this chapter we begin broadly by outlining the mechanisms by which these
adaptations come about: the evolutionary process of speciation, convergence, and
radiation. We then focus in on the methods by which the genetic constitution of
individuals, or groups of individuals, can be determined and the importance of such
information in wildlife management.
To understand why a population of a species lives where it does, that is to explain its
distribution in nature, we should know how an individual is adapted to its environ-
ment, what types of environment it encounters, and what resources are available.
An adaptation is defined as “a trait that increases fitness relative to an alternative
trait” (Schluter 2000). When we talk about the adaptations of individuals we mean
the way in which an animal fits into its environment and uses its resources. The
adaptive characters that describe an individual – its physical attributes (morphology),
physiology, and behavior – are determined first by the processes of natural selection
and secondly by its history over evolutionary time, its phylogeny.
The physical environment – temperature, humidity, and other features that we call
the abioticenvironment – together with the effects of other species which form the
food, competitors, and predators (the bioticenvironment), acts through natural selec-
tion to produce a suite of adaptations which are called life-history traits.
The term “evolution” refers simply to change in a population over time. It does not
necessarily mean speciation (although this may be an outcome) and it does not imply
a mechanism of change. The idea of evolution was already being talked about in Europe
in the early 1800s, albeit as a radical concept. Charles Darwin described a mechanism
for this change in his book On the Origin of Speciesin 1859. It was called natural
selection and proposed jointly by Darwin and A.R. Wallace in 1858. Darwin based
his theory on three observations:
1 Populations increase geometrically through reproduction.
2 All individuals are different – the genetic mechanism for this was demonstrated
later by Gregor Mendel (Mendel 1959).
3 Populations remain constant (at least within broad limits) due to a lack of
resources. The relative stability of populations was first noted by Malthus (1798) in
his essay on populations. From these observations there follow two postulates.
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3.1 Introduction
3.2 Adaptation
3.3 The theory of natural selection
