Conservation Genetics

Conservation Biology + Genetics = Conservation Genetics

Destroying or changing habitats can endanger the animals, plants, and other organisms that live there. By effective managing these ecosystems, we can help preserve threatened and endangered species.

The science of Conservation Biology looks at individuals and populations that have been affected by habitat loss, exploitation, and/or environmental change. Information gained from studying these organisms informs decisions that will ensure their survival into the future.

The science of Genetics looks at inherited characteristics and the genes that underlie them.

Put the two together and you get the science of Conservation Genetics.

Conservation genetics uses a combination of ecology, molecular biology, population genetics, mathematical modeling, and evolutionary taxonomy (the study of family relationships). It is both a basic and an applied science. First, scientists must understand the genetic relationships among the organisms they're studying. Then wildlife managers use techniques to preserve biological diversity in these species.

The organisms that conservation geneticists study usually belong to endangered or threatened populations. To develop ways to help these populations, scientists ask two questions: What has brought these populations to the brink of extinction, and what steps can we take to reverse this trend? Information about the genetic diversity of the organisms under study helps scientists and managers form strategies to

Past conservation efforts have addressed populations from a mathematical, evolutionary, or taxonomic point of view. Modern efforts include genetic studies, giving conservation scientists and ecological managers much more information about the diversity among the individuals in a population. Without genetics, we may conserve the wrong population or waste valuable resources on a population that isn't endangered!

To measure the genetic diversity of a particular gene, scientists look at how many different versions of it (called alleles) are present in a population. For example, one gene may determine the flower color of a plant. Different alleles may exist for that gene (e.g., a pink allele, a purple allele, and a white allele). In each case, the same gene determines flower color—but the exact order of DNA letters that make up the gene are different for each allele. When all or nearly all members of a population have the same allele, that population is said to have low genetic diversity at that gene. But when many different versions of the gene exist in a population, the population has high genetic diversity at that gene.

Why is genetic diversity important?

Populations or species with low genetic diversity at many genes are at risk. When diversity is very low, all the individuals are nearly identical. If a new environmental pressure, such as a disease, comes along, all of the individuals within the population may get the disease and die. But in a population with high genetic diversity, chances are better that some individuals will have a genetic makeup that allows them to survive. These individuals will reproduce, and the population will survive.

The genetic diversity of a species is always changing. No matter how many variants of a gene are present in a population today, only the variants that survive in the next generation can contribute to species diversity in the future. Once gene variants are lost, they cannot be recovered.

Habitat Destruction

When habitat destruction or other factors put a population at risk, scientists and conservation managers may target that population for investigation. For example, they may study a population of plants whose habitat will be destroyed by the building of a new shopping mall. Or they may study duck and geese populations when new hunting regulations have been put in place.

Human interference is not the only danger to plants and animals. Natural factors, such as storms and diseases, can also cause populations to dwindle.

Change in Population Size

Surveillance of small populations is critical, because they are particularly sensitive to change. Random or unpredictable events such as natural catastrophes, environmental changes, or genetic mutations can cause a sudden decrease in population size. When the population of a species is small to begin with, further reduction of their remaining numbers can sharply reduce genetic diversity.

Small populations are also more sensitive to genetic drift, as well as the problems that come with geographic isolation and establishing a new population from only a few individuals (founder effect). Each of these factors affects which individuals will give rise to the next generation, and therefore which alleles will be passed on.

With each generation, some individuals survive to reproduce and pass on their genes, while others are eliminated. Over time, individual alleles can become more or less common in a population. When inherited characteristics determine who will survive and who will not, the process is called natural selection. When random factors determine who will survive, the process is called genetic drift. Through genetic drift, some alleles can entirely disappear from a population.

A small population is more susceptible to genetic drift than a large population. When just a few individuals carry a particular allele, it becomes more likely that just by chance those individuals will not reproduce, and the allele will be lost.

Sometimes even a large population can lose genetic diversity. One way loss can happen is through geographical isolation. Geographical isolation can happen if a new barrier is imposed through a habitat. For example, if a river changes course or a new housing subdivision is built, a population of plants or animals may be divided into two groups. Just by chance, the pool of gene variants in the two separated populations may differ from one another.

As an example, imagine a flower species with two forms that share a habitat. A new subdivision, including new houses and roads, divides the habitat, isolating the two forms to different areas. The first form, a tall, sturdy plant with few flowers, is isolated to the north end of the subdivision, while the second form, a more delicate plant with prettier flowers, is isolated to the south end. Even though the new homeowners may preserve both populations, the two are sufficiently isolated from each other that they can no longer exchange genes. In this situation, each type is exposed to environmental pressures without the ability to crossbreed with the other type to form plants with new, perhaps more advantageous, combinations of genes. The new pressures created by building the development may affect the two types of plants differently. For example, the more-delicate variety might die from a lack of shade caused when trees were cut down for the subdivision. When they are gone, so is the allele responsible for the attractive flower—and the overall population size decreases.

Conservation geneticists use DNA data from an organism to inform management choices. As in any scientific field, conservation scientists use a defined approach to their work:

Identification, Inventory, and Analysis

1. Define populations and areas of interest. Because there are so many species of organisms, endangered or threatened species usually take priority.
2. Observe the population. What are the known forms of the species? What are known or suspected relatives of the species? What are the physical characteristics used to classify the different forms and species?
3. Form hypotheses about relationships between populations and/or species and test these hypotheses by examining genetic characteristics of the organisms (DNA or protein data).
4. Use mathematical models to analyze the data. Determine how much diversity exists in separate populations of the species, as well as the rate at which genes are exchanged among populations (gene flow).

Interpretation and Management

Scientists and managers work together to identify endangered organisms. To begin to develop a management strategy, they investigate the organism's habitat:

1. Determine the degree to which the organism is adaptable to various temperatures, soils, and water conditions.
2. Examine factors that influence genetic diversity, such as the identity and characteristics of plant pollinators. The health and welfare of pollinating species may be critical to the survival of an endangered plant species.
3. Study threats to the integrity of the species' habitat, including human, climatic, and other factors.

Once all of the aspects of the population and its environment are understood, scientists and managers can develop an intelligent preservation plan.