Genetic Diversity – Understanding Conservation at Genetic Levels

In this chapter, you will learn about:

• 1. Why genetic concerns are central to the study of conservation biology

• 2. How to measure the genetic attributes of individuals and populations

• 3. Why inbreeding can pose threats to population persistence

• 4. The roles of hybridization and introgression in conserving biodiversity

Conservation biology is a science concerned with the fate of populations, which are defined and identified by their genetic constituency. This unique genetic makeup not only distinguishes them from other populations, but also determines their capacity to adapt to changing conditions and, potentially, to produce new species. Many conservationists would argue that the conservation of genetic diversity is the foundational basis of all conservation efforts because genetic diversity is requisite for evolutionary adaptation, and such adaptation is the key to the long-term survival of any species (Schemske et al. 1994). To assure such survival, conservation biologists have two primary goals in the area of genetics. One is to preserve significant amounts of heritable genetic variation, particularly in small populations threatened with extinction. The other is to prevent the fixation of deleterious alleles, a fixation that can contribute to reduced fitness and accumulation of harmful mutations (Lynch 1996). Preserving high levels of heritable variation helps to retain a population’s current reproductive fitness and maintain its evolutionary potential, its capacity to adapt to environmental change over the long term. Preventing the fixation of deleterious alleles is intended to prevent declines in survivorship and fecundity that often occur in small populations as a result of reduced genetic diversity. Thus, the two goals are intimately related, and the overall aim and application of conservation genetics is to preserve species not simply as static forms, but as dynamic entities capable of responding to and coping with environmental change through time. Only when species possess this kind of adaptive potential do they have a reasonable expectation of persistence in a changing world, and only through maintaining their genetic diversity can they hope to possess this potential.

To achieve these goals, conservation genetics today encompasses three categories of activities: (1) genetic management of small populations to maximize the retention of genetic diversity and minimize inbreeding, (2) resolution of taxonomic uncertainties and delineation of management units based on genetic characteristics of populations, and (3) use of genetic analyses in forensics, especially in the enforcement of conservation laws and treaties, and in understanding the biology of target species. We will examine each category in detail in this and the next chapter to understand and appreciate the significance of the kinds of approaches and techniques that can be used in each of these categories. In this chapter, we will develop a conceptual understanding of conservation genetics, including its history, development, and theoretical framework. In the following chapter (Chapter 7), we will address more specific applications of genetic knowledge, skills, and techniques in actual conservation management. We begin with an overview of the foundations of conservation genetics.