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Richard Frankham
tested in controlled replicated studies. Until recently, this area of conservation
genetics has been sadly neglected.
The objectives of this chapter are to define the appropriate role for laboratory
studies in conservation genetics, to illustrate this with examples mainly from our
laboratory, and to point to other studies that need to be done using laboratory
species.
Essential Interplay of Theory and Experimentation
An evolving population is a complex system in which multiple genes in linkage
groups are subject to mutation, migration, natural selection, and the random
events of meiosis. The behavior of the system depends on the breeding system and
environmental conditions. One approach to understanding such a complex system
is as follows:
1. Build simple mathematical models, firstly keeping all factors constant, then
varying one factor at a time, then two factors, and so on.
2. Experimentally evaluate the predictions of the models.
3. On the basis of the experimental results, refine the theoretical models.
4. Subject the refined models to experimental evaluation (i.e., the process of
model development, evaluation/monitoring, and redevelopment should be
cyclic and ongoing).
Such approaches have been used in quantitative genetics, population genetics,
and animal breeding and should be used in conservation genetics. A relevant
example of this interplay between theory and experimentation is provided by
investigations into factors affecting the long-term evolution of populations. Following the rediscovery of Mendelian inheritance, the multiple-factor hypothesis
was developed to explain quantitative genetic variation and experimentally validated (East 1916). Equations were developed to predict response to selection
(Fisher 1918; Wright 1921; Lush 1945). These provided reasonable predictions in
the short term (Clayton et al. 1957) but not in the long term (Clayton and
Robertson 1957). As a consequence, Robertson (1960) developed a theory of
limits in artificial selection, based on the loss of genetic variation in finite population sizes and the effects of selection (chance plus selection). Experimental evaluation of this theory in Drosophila (Jones et al. 1968) and mice (Eisen 1975)
revealed qualitative agreement with predictions but limited quantitative predictability. This work established that larger populations showed more potential for
evolutionary change. Genetic analyses of selection lines established that mutations occurring in the lines contributed to long-term selection response (Hollingdale 1971; Frankham et al. 1978; Frankham 1980, 1982; Yoo 1980). Hill
(1982) extended the theory of limits in artificial selection by adding mutation to
chance and selection. Predictions of Hill’s theory have subsequently been evaluated (Frankham 1983; Lopez-Fanjul and Caballero 1990). This is an object lesson
Richard Frankham
tested in controlled replicated studies. Until recently, this area of conservation
genetics has been sadly neglected.
The objectives of this chapter are to define the appropriate role for laboratory
studies in conservation genetics, to illustrate this with examples mainly from our
laboratory, and to point to other studies that need to be done using laboratory
species.
Essential Interplay of Theory and Experimentation
An evolving population is a complex system in which multiple genes in linkage
groups are subject to mutation, migration, natural selection, and the random
events of meiosis. The behavior of the system depends on the breeding system and
environmental conditions. One approach to understanding such a complex system
is as follows:
1. Build simple mathematical models, firstly keeping all factors constant, then
varying one factor at a time, then two factors, and so on.
2. Experimentally evaluate the predictions of the models.
3. On the basis of the experimental results, refine the theoretical models.
4. Subject the refined models to experimental evaluation (i.e., the process of
model development, evaluation/monitoring, and redevelopment should be
cyclic and ongoing).
Such approaches have been used in quantitative genetics, population genetics,
and animal breeding and should be used in conservation genetics. A relevant
example of this interplay between theory and experimentation is provided by
investigations into factors affecting the long-term evolution of populations. Following the rediscovery of Mendelian inheritance, the multiple-factor hypothesis
was developed to explain quantitative genetic variation and experimentally validated (East 1916). Equations were developed to predict response to selection
(Fisher 1918; Wright 1921; Lush 1945). These provided reasonable predictions in
the short term (Clayton et al. 1957) but not in the long term (Clayton and
Robertson 1957). As a consequence, Robertson (1960) developed a theory of
limits in artificial selection, based on the loss of genetic variation in finite population sizes and the effects of selection (chance plus selection). Experimental evaluation of this theory in Drosophila (Jones et al. 1968) and mice (Eisen 1975)
revealed qualitative agreement with predictions but limited quantitative predictability. This work established that larger populations showed more potential for
evolutionary change. Genetic analyses of selection lines established that mutations occurring in the lines contributed to long-term selection response (Hollingdale 1971; Frankham et al. 1978; Frankham 1980, 1982; Yoo 1980). Hill
(1982) extended the theory of limits in artificial selection by adding mutation to
chance and selection. Predictions of Hill’s theory have subsequently been evaluated (Frankham 1983; Lopez-Fanjul and Caballero 1990). This is an object lesson