22
C. Moritz
1 Introduction
The need to protect genetic diversity, as well as that of species and ecosytems is
widely recognised (Noss 1990) and has been acknowledged in international agreements (e.g. the Convention on Biological Diversity) as well as policies of many
national governments. However, appropriate measures and strategies for protecting genetic diversity remain ill-defined and this, together with the lack of baseline
information for most systems, is a substantial impediment to practical efforts to set
conservation priorities. At one level genetic diversity can be considered as the total
information content represented by a suite of species or higher taxa, leading to the
use of various phylogenetic measures of distinctiveness in weighting schemes (VaneWright et al. 1991; reviewed in Humphries et al. 1995; Crozier 1997). At the other
extreme is consideration of the level of genetic diversity within popUlations and the
relationship between diversity and the potential response to selection (Frankel and
Soule 1981).
Some clarity can be achieved by considering the underlying conservation goalwhat are we trying to protect and what is the most efficient means of doing so? In
an eloquent paper, Frankel (1974) stressed the need to maintain evolutionary processes in increasingly modified systems and advocated the development of an evolutionary ethic in conservation and, more generally, in society. We can define the
following overarching goal:
To maintain evolutionary processes and the ecological viability of populations and landscapes necessary to achieve this.
This acknowledges that both genetic diversity and ecological processes are necessary to maintain continuing evolution. However, while viability of populations and
ecosystems is necessary, it may not be sufficient. It follows that successful conservation strategies will draw on understanding of both ecological and evolutionary
processes, combined with socio-economics.
2 Components of Genetic Diversity and
Conservation Strategy
In recent years, there has been increasing debate over concepts and criteria for
recognising intraspecific units for conservation. Traditionally, conservation managers have sought to protect taxonomically recognised entities - species and subspecies. However, surveys of molecular variation have often revealed a lack of
congruence between subspecies defined on morphological criteria and neutral molecular markers (Avise and Ball 1990; O'Brien and Mayr 1991), the former presumably reflecting the joint action of selection and history, and the latter history
alone. The' concept of an "Evolutionarily Significant Unit" (ESU) was developed
in order to provide an objective approach to prioritising intraspecific units for protection (Ryder 1986) and was subsequently refined for applications under the USA
Endangered Species Act (Waples 1991, 1995).
C. Moritz
1 Introduction
The need to protect genetic diversity, as well as that of species and ecosytems is
widely recognised (Noss 1990) and has been acknowledged in international agreements (e.g. the Convention on Biological Diversity) as well as policies of many
national governments. However, appropriate measures and strategies for protecting genetic diversity remain ill-defined and this, together with the lack of baseline
information for most systems, is a substantial impediment to practical efforts to set
conservation priorities. At one level genetic diversity can be considered as the total
information content represented by a suite of species or higher taxa, leading to the
use of various phylogenetic measures of distinctiveness in weighting schemes (VaneWright et al. 1991; reviewed in Humphries et al. 1995; Crozier 1997). At the other
extreme is consideration of the level of genetic diversity within popUlations and the
relationship between diversity and the potential response to selection (Frankel and
Soule 1981).
Some clarity can be achieved by considering the underlying conservation goalwhat are we trying to protect and what is the most efficient means of doing so? In
an eloquent paper, Frankel (1974) stressed the need to maintain evolutionary processes in increasingly modified systems and advocated the development of an evolutionary ethic in conservation and, more generally, in society. We can define the
following overarching goal:
To maintain evolutionary processes and the ecological viability of populations and landscapes necessary to achieve this.
This acknowledges that both genetic diversity and ecological processes are necessary to maintain continuing evolution. However, while viability of populations and
ecosystems is necessary, it may not be sufficient. It follows that successful conservation strategies will draw on understanding of both ecological and evolutionary
processes, combined with socio-economics.
2 Components of Genetic Diversity and
Conservation Strategy
In recent years, there has been increasing debate over concepts and criteria for
recognising intraspecific units for conservation. Traditionally, conservation managers have sought to protect taxonomically recognised entities - species and subspecies. However, surveys of molecular variation have often revealed a lack of
congruence between subspecies defined on morphological criteria and neutral molecular markers (Avise and Ball 1990; O'Brien and Mayr 1991), the former presumably reflecting the joint action of selection and history, and the latter history
alone. The' concept of an "Evolutionarily Significant Unit" (ESU) was developed
in order to provide an objective approach to prioritising intraspecific units for protection (Ryder 1986) and was subsequently refined for applications under the USA
Endangered Species Act (Waples 1991, 1995).