Conservation genetics is a field that combines different areas of study, such as population genetics, to understand how genes function in populations. This helps manage natural resources, protect genetic diversity, and prevent species from becoming extinct. Scientists working in this field come from various backgrounds, including population genetics, natural resource management, molecular ecology, molecular biology, evolutionary biology, and systematics. Genetic diversity within species is one of the three main parts of biodiversity, along with species diversity and ecosystem diversity. Because of this, it plays an important role in the broader field of conservation biology.
Genetic diversity
Genetic diversity refers to the variety of genetic differences found within a species. Scientists measure it using several methods, such as observed heterozygosity, expected heterozygosity, the average number of gene versions at each genetic location, the percentage of genetic locations with multiple versions, and an estimate of the effective population size. At the population level, genetic diversity is important for conservation because it affects the health of individuals and the long-term survival of populations. Lower genetic diversity is linked to weaker individual fitness, such as higher rates of young animal deaths, weaker immune systems, slower population growth, and a greater risk of extinction.
Heterozygosity, a key measure of genetic diversity, helps determine a population’s ability to survive environmental changes, new diseases, and maintain fitness across generations. It is closely related to population size, which is vital for conservation efforts. Generally, smaller populations have lower heterozygosity compared to larger populations. This reduced genetic diversity makes small populations more vulnerable to challenges like disease and environmental shifts.
In small populations, repeated breeding between close relatives increases the chance of inbreeding depression, which lowers the average fitness of individuals. Inbreeding leads to offspring with lower heterozygosity (more homozygosity), meaning they inherit the same gene versions from both parents. For example, an individual with the same maternal and paternal grandparent is more likely to have identical gene versions than someone with unrelated grandparents.
High homozygosity (low heterozygosity) reduces fitness because it increases the chance of harmful recessive genes being expressed. Natural selection can favor genes that reduce the harm of homozygosity, such as the sickle-cell beta-globin gene. This gene remains common in areas with malaria because having one copy of the gene provides protection against the disease, while having two copies causes health problems.
Low genetic diversity also limits the mixing of genes during reproduction, reducing the creation of new gene combinations. This makes it harder for natural selection to remove harmful genes and promote beneficial ones. For example, if two genes on the same chromosome affect fitness differently, selection cannot act on them separately unless recombination (gene mixing) occurs. Recombination allows beneficial gene versions to spread and harmful ones to decrease, but only if alternative gene versions exist.
The relationship between genetic diversity and population size is clear in the Watterson estimator, a method that measures genetic diversity based on population size and the rate of new gene mutations. It is important to identify populations at risk of losing genetic diversity before problems occur. Once lost, genetic diversity can only be restored through mutations or gene flow from other populations. If a species is nearly extinct, there may be no other populations to help restore diversity. Smaller populations gain diversity more slowly than larger ones because fewer individuals contribute to genetic changes.
Contributors to extinction
Species extinction happens because of many reasons. When closely related animals or plants mate, it can lower the health and survival chances of the group. This is called inbreeding depression. Over time, harmful gene combinations may increase, making populations more likely to get sick and have fewer babies. Small groups that mate with close relatives might also develop more harmful genetic changes, which can worsen their health further.
Population fragmentation can also lead to extinction. When habitats are destroyed or natural events separate groups, populations may become isolated. These smaller, separated groups often have limited contact with others, which can cause inbreeding.
If two groups with very different genes mate, outbreeding depression can occur. This can harm the health of one or both groups, just like inbreeding depression. Some conservation efforts study the genetic differences between groups of the same species. However, outbreeding depression might reduce the success of these efforts.
Techniques
Scientists use specific genetic methods to study the DNA of species to understand conservation problems and how populations are organized. This analysis can be done using DNA from living individuals or from DNA found in remains from the past.
Techniques used to compare differences between individuals and populations include:
1. Allozymes
2. Random fragment length polymorphisms
3. Amplified fragment length polymorphisms
4. Random amplification of polymorphic DNA
5. Single strand conformation polymorphism
6. Minisatellites
7. Microsatellites
8. Single-nucleotide polymorphisms
9. DNA sequencing
Each technique focuses on different parts of the genome in animals and plants. The choice of technique depends on the information needed. For example, mitochondrial DNA in animals changes quickly over time, making it useful for showing differences between individuals. However, it is only passed from mothers and is small in size. In plants, mitochondrial DNA changes in structure often, so it is rarely used. Instead, chloroplast DNA is used because it is more stable. Other parts of the genome, such as the major histocompatibility complex and microsatellites, are also commonly studied because they change frequently.
These methods help scientists learn about long-term genetic diversity and understand issues like population history and ecology.
Another method uses historic DNA, which is DNA from remains found in museums or caves. Historic DNA is valuable because it helps scientists see how species responded to past environmental changes, which can help predict how similar species might react in the future.
Museums are useful because they hold many species’ remains for scientists worldwide. However, cave remains provide a longer view of past changes without disturbing living animals.
Noninvasive monitoring is another technique that uses DNA from organic material left behind by animals, such as feathers. Environmental DNA (eDNA) can be collected from soil, water, or air. Animals leave cells in the environment, and when these cells break down, DNA is released. This method avoids disturbing animals and can reveal details about their sex, movement, family relationships, and diet.
Other methods help reduce genetic problems that can lead to extinction. For example, inbreeding (when closely related animals reproduce) can be reduced by increasing genetic diversity. This can be done by bringing in new individuals, breeding older animals to extend generations, or balancing family sizes to increase population numbers. Harmful traits from inbreeding can be removed through natural selection or by breeding out these traits.
Animals raised in captivity may develop traits that are not helpful in the wild, such as reduced ability to survive outside. Techniques that increase genetic diversity, create captive environments similar to the wild, and reduce population grouping can help prevent these issues.
Solutions to prevent extinction often overlap because the causes of extinction are connected. For example, harmful genetic changes can arise from inbreeding, and reducing inbreeding also helps prevent these changes from becoming common.
Applications
These techniques are used in many different ways. One example is helping scientists define species and subspecies of salmonids. Mixing of different species, called hybridization, is a big problem for salmonids. This issue affects conservation, politics, social groups, and the economy.
A specific example is the Cutthroat Trout. Studies of its special types of DNA and proteins show that mixing between native and non-native species has greatly reduced its population. To help native fish reproduce better, some mixed populations have been removed. These situations affect local fishermen and larger businesses, like those in the timber industry.
Defining species and subspecies also helps protect mammals. For example, the northern white rhino and southern white rhino were once thought to be the same species because they look similar. However, recent DNA studies showed they have different genes. Because of this, the northern white rhino population has nearly disappeared due to poaching. The idea that they could breed with southern rhinos was wrong and has hurt conservation efforts.
New uses include using DNA to identify animals in poaching cases. DNA databases help track trade of protected species, stop illegal trading of animal parts, and fight poaching. Conservation genetics can work with other scientific fields. For example, landscape genetics has been used with conservation genetics to find animal movement paths and barriers that help plan better conservation strategies.
Development and history
Conservation genetics uses genetic rules and tools to manage and protect biodiversity. It combines knowledge from biology, population genetics, bioinformatics, and ecology to study how genes affect the survival, reproduction, and ability of species to adapt. This helps create plans to stop species from becoming extinct. Early ideas focused on keeping genetic diversity to help populations avoid problems like inbreeding, disease, and changes in the environment. Studies later showed that small or bottlenecked populations, like elephant seals and cheetahs, often have less genetic variation and face challenges in survival and health. These findings were written about in important books that explained how genetics should be used in conservation efforts.
From the 1970s to the 1990s, methods improved from using allozymes to techniques like restriction fragment length polymorphisms (RFLPs), PCR-based mitochondrial DNA tests, and nuclear DNA markers such as microsatellites and SNPs. These changes allowed scientists to study genetic differences in wild populations more clearly. Early uses of molecular tools included analyzing DNA in black rhinoceroses, tracking whales through forensic genetics, and creating systems to monitor genetic changes. Examples showed that genetic restoration could help populations recover from inbreeding, as seen in Florida panthers.
By the 2000s–2010s, next-generation sequencing (NGS) helped shift from conservation genetics to conservation genomics. This allowed scientists to study thousands to millions of genetic locations and entire genomes to understand biodiversity, population size, movement, and adaptation. Practical advice on using reduced-representation and low-coverage whole genome sequencing strategies, along with trade-offs and filtering methods, made these tools more accessible for non-model species.
Genome assemblies, which were once a major challenge, improved greatly through international projects like Genome 10K and the Vertebrate Genomes Project. These efforts created detailed, chromosome-level reference genomes that help guide conservation decisions. With these resources, studies have revealed how aquatic species like otters adapt, refined understanding of evolutionary history in carnivores, and provided tools for forensic wildlife management and monitoring populations outside their natural habitats.
Genomic time series, ROH scans, and load estimation have shown how population bottlenecks and inbreeding affect survival and extinction risk in species like northern elephant seals and killer whales. At the same time, genomics continues to support conservation through genetic monitoring, moving animals to new areas, cloning to save genetic diversity, and forensic tools for policy decisions.
A major challenge is building equal global capacity because knowledge and resources are not evenly spread. International training programs, such as the "Recent Advances in Conservation Genetics" course started by Stephen J. O'Brien and supported by the American Genetic Association, have helped share methods, standardize analysis, and connect researchers to high-performance computing resources and reproducible workflows. Examples include open tutorials, cloud-based environments, and teaching practices that focus on collaboration and reproducibility. Other programs, like Physalia and ConGen Population Genomic Data Analysis, also help expand access to modern genetic analysis tools.
Conservation genomics now guides decisions about saving species through genetic rescue, reintroducing animals to the wild, and addressing ethical questions about de-extinction, assisted reproduction, and new technologies. Research on many species, such as parrots, solenodons, and echinoderms, shows how community-driven genome projects and marker development support both on-site and off-site conservation strategies while training future scientists.
As the field grows, studies emphasize the importance of genome-wide genetic variation for species survival, the need to include genetic essential biodiversity variables in conservation policies, and the value of cross-disciplinary training to apply methods in real-world situations. Reviews and perspectives also highlight the need to turn genomic findings into practical conservation actions, especially in regions where resources are still limited.
Implications
New technology in conservation genetics is changing how scientists protect animals and plants. At the tiny parts of living things, scientists use tools like minisatellites and MHC to study genetic information. These tools help scientists understand how species are related, find the best animals to bring back to a population for recovery, and determine family connections. These discoveries affect more than just animals and plants—they also influence how humans live, work, and make decisions. In nature, having more genetic differences among plants and animals helps ecosystems recover, as seen in a group of grasses that resisted damage from geese because of their genetic variety. Since more species mean healthier ecosystems, using new genetic tools to protect biodiversity has bigger effects than before.
A short list of studies a conservation geneticist may research includes:
- How scientists group species, subspecies, and populations based on their family tree, and how to measure how unique these groups are.
- Finding hybrid animals or plants, studying how different species mix in nature, and learning about the history of genetic mixing between species.
- Studying the genetic makeup of wild and managed populations, including identifying important groups of animals or plants that need special care for conservation.
- Measuring genetic differences within a species or population, especially in small or endangered groups, and calculating how many individuals effectively contribute to genetic diversity.
- Studying the problems caused by breeding too closely or too far apart, and how genetic variety affects the health and survival of animals.
- Looking for signs that animals or plants are choosing mates or having babies differently in areas where their environment has changed.
- Using genetic tools to stop illegal trade of endangered species.
- Creating methods to track and increase genetic diversity in animals raised in captivity and reintroduced to the wild, including using math models and real-life examples.
- Studying how introducing genetically modified organisms affects conservation efforts.
- Examining how pollution and other environmental changes affect the health and ability of organisms to adapt, such as how some animals change color to survive in polluted areas.
- Developing new ways to study genetic information without harming the animals or plants being studied.
- Tracking genetic differences in populations and studying which genes help animals or plants survive better in their environments.