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14
Role of Genetics in
Conservation Biology
Sabine S. Loew
Introduction
Many species are represented solely by populations that are highly fragmented,
isolated, or captive and therefore lack the number of individuals considered necessary for healthy sustainable populations. These species run an increased risk of
local and global extinction due to environmental, demographic, and genetic stochasticity (Shaffer 1981) and may benefit from special management attention.
Two major goals of conservation genetics are to minimize loss of genetic variation
in managed populations and define the taxonomic units (i.e., rare populations,
subspecies, species) we ought to conserve. In this chapter, I outline the rationale
for managing genetic diversity, introduce molecular tools available to assess
genetic variation and taxonomic relationships, and provide examples illustrating
applications of population genetics to conservation biology. This chapter is not an
exhaustive review. The discussion applies to many captive and natural threatened
populations ranging from insects to primates. The apparent bias among the examples toward mammals and birds is not a value statement but simply a reflection of
the general interest in conservation biology toward higher vertebrates as well as
my own background in mammalian biology.
Concept of Genetic Diversity
The genetic composition of a population can be described by the alleles present at
different loci for a representative sample of individuals within a population.
Genetic diversity can be quantified by the number and distribution of alleles
within and between individuals and populations. Diploid organisms have two
alleles per locus. Individuals are considered homozygous at this locus if both
alleles are the same and heterozygous if they are different from one another.
Genetic variation can be described at a single locus or multiple loci by using
several methods (Lande and Barrowclough 1987; Lacy et al. 1995; Hamrick and
Godt 1996). For example, a polymorphic locus is defined as having several alleles
14
Role of Genetics in
Conservation Biology
Sabine S. Loew
Introduction
Many species are represented solely by populations that are highly fragmented,
isolated, or captive and therefore lack the number of individuals considered necessary for healthy sustainable populations. These species run an increased risk of
local and global extinction due to environmental, demographic, and genetic stochasticity (Shaffer 1981) and may benefit from special management attention.
Two major goals of conservation genetics are to minimize loss of genetic variation
in managed populations and define the taxonomic units (i.e., rare populations,
subspecies, species) we ought to conserve. In this chapter, I outline the rationale
for managing genetic diversity, introduce molecular tools available to assess
genetic variation and taxonomic relationships, and provide examples illustrating
applications of population genetics to conservation biology. This chapter is not an
exhaustive review. The discussion applies to many captive and natural threatened
populations ranging from insects to primates. The apparent bias among the examples toward mammals and birds is not a value statement but simply a reflection of
the general interest in conservation biology toward higher vertebrates as well as
my own background in mammalian biology.
Concept of Genetic Diversity
The genetic composition of a population can be described by the alleles present at
different loci for a representative sample of individuals within a population.
Genetic diversity can be quantified by the number and distribution of alleles
within and between individuals and populations. Diploid organisms have two
alleles per locus. Individuals are considered homozygous at this locus if both
alleles are the same and heterozygous if they are different from one another.
Genetic variation can be described at a single locus or multiple loci by using
several methods (Lande and Barrowclough 1987; Lacy et al. 1995; Hamrick and
Godt 1996). For example, a polymorphic locus is defined as having several alleles