Date of this Version
KEY TOPICS IN CONSERVATION BIOLOGY, edited by David W. Macdonald & Katrina Service. (2007).
Conservation biology strives to conserve biodiversity and biological processes in ecosystems, of which genetic variation is a key component. Genetic variation is the underlying foundation of higher levels of biodiversity (e.g. populations and species). Without genetic variation, populations could not evolve and adapt to future environmental changes. Because DNA (deoxyribonucleic acid) is fundamental to all biological systems, the practice of conservation often requires genetic studies. Beyond the measurement and conservation of genetic variation per se, the uses of molecular genetic techniques in conservation biology include:
1. identification of individuals, species, populations and conservation units;
2. detection of hybrid zones and admixed populations;
3. quantification of dispersal and gene flow;
4. estimation of current and historical population size;
5. assessment of parentage, relatedness, reproductive success, mating systems and social organization.
Molecular markers also assist forensic detection of illegally killed and trafficked plants and animals or their body parts. Finally, markers that are under selection (and thus influence fitness) can identify locally adapted populations that could have special value for conservation.
Two developments in molecular biology have had unprecedented significance for conservation biology: the PCR (polymerase chain reaction) process and the discovery of microsatellites. Since its development in 1985, PCR has transformed the life sciences, including conservation biology, due to the ease (and still declining cost) with which it generates millions of copies of any DNA fragment from minuscule quantities. The PCR technique has allowed the non-destructive study of living specimens and their long-dead ancestors. A surge of mitochondrial DNA (mtDNA) sequence studies on phylogeny, hybridization and gene flow among populations ensued, including some based on fragments of museum skins and specimens preserved in ethanol (Brown & Brown 1994). For example, ancient bones of the Laysan duck (Anas laysanensis) were identified by mtDNA analysis from lava tubes on the main Hawaiian islands, where they apparently had become extinct (Cooper et al. 1996). These data justified reintroduction and suggested that many island endemics may be relics of former cosmopolitan species (Wayne et al. 1999).
Microsatellites consist of a length of DNA in which sequences of one to four nucleotides are repeated many times (e.g. [AC]n, where n = 5 to 50 repeats). The number of repeats defines an allele at a locus. Microsatellites are typically highly variable, often with > 10 alleles per locus in a population. They are widely dispersed in eukaryotic genomes and inherited in a Mendelian fashion. They can be amplified by PCR from only tiny amounts (one-to-several molecules) of DNA and thus can be salvaged from partially degraded DNA, such as in museum skins, dried faeces or fossil bones. Because of these features, microsatellites have become the most widely used molecular genetic marker. Numerous other PCR-based molecular markers and analysis systems exist, including SNPs (single nucleotide polymorphisms), and direct sequencing of PCR products (see Sunnucks (2000), Morin et al. (2004) and (Schlotterer 2004) for reviews).
Genetics is a key component of many aspects of conservation biology. From the design of reserves to the management of breeding programmes, molecular techniques are indispensable and are increasingly being used to address questions of conservation relevance. Molecular biology is undoubtedly the fastest evolving field of science. Conservation biologists can make use of these emerging techniques, which are rapidly transforming the field to one that is more molecular oriented. Conservation biology is an inexact science because new crises emerge every day and in most cases solutions are but extrapolations from related cases. Molecular biology is helping to change that trend by allowing conservation biologists to quickly scan a wide range of individual and population characteristics at a given site. Genetic data are most useful in conjunction with more traditional data, such as demographics, life history, distribution, etc. Rapid gain of detailed information on a population at risk may allow better understanding of the system at hand, and more sound recommendations for the decision makers.