Genetic diversity is the variation of genes that exist within a species population. Genes are what make up our unique DNA code, carrying information that determines certain features or characteristics about you. These are called traits. Every individual in a species is unique because of these differences in traits.
Think about your family and how you are all related yet each of you are different in your own way, either by physical differences, like being shorter or taller, or by differences in the way you think or behave, like being very social, more of a book-reader, or more creative and arty.
Genetic diversity comes from changes in our DNA sequence that occur during cell replication. These changes are referred to as mutations. Most of the time these changes aren’t particularly beneficial or have no effect at all. But every now and again, a mutation will occur that provides a benefit to the individual which can be passed on to their offspring during reproduction.
With each generation, more and more mutations are added to the DNA in a species’ gene pool. One of these mutations could be a solution to changes in the environment. For example, if mutations in a particular primate result in webbed hands, this could have no effect. But if the individual lives near a waterway, as is the case for the proboscis monkey, and predator populations in the area have grown, having webbed hands gives an advantage in how they can escape through the waterways. Their ability to swim more efficiently provides a faster escape route that most predators cannot follow. It may also open up new foraging and nesting sites, as well as potential mating opportunities as waterways wouldn’t restrict their ability to move throughout their environment.
Think of a species with huge genetic diversity like a hardware store that contains all the tools, equipment, and materials needed for almost every situation. A species with very little genetic diversity is more of a basic toolbox with some tools available to them. Some can be used to fix a problem, but they may not be perfect for the job. Or, worse, none of the tools they have are suitable for the jobs they’re needed for.
Having a variety of characteristics allows a species to survive diseases, environmental changes, and ecosystem stresses because some individuals may possess certain traits that allow them to overcome such impacts of change. Individuals may die out, but the species will survive.
Let’s take a closer look and see the role genetic diversity plays in the evolution of a family of animals:
Fifty to sixty million years ago, the first lemurs arrived on the island of Madagascar, without any predators to regulate their numbers. Their populations grew exponentially, leading to intense competition for resources, such as food and shelter. Individuals who could not compete with others for these resources were forced to change their behavior, diet, and/or location on the island to ensure they could obtain enough resources to survive and reproduce:
- Individuals who evolved into the aye-aye became nocturnal feeders, with an elongated middle finger used as a tool for scooping out fruit flesh and tapping along branches in search of insects under that bark.
- Ancestors of the golden bamboo lemur migrated to the island’s southeastern bamboo forest and marshes, developing an impressive digestive system that allows them to consume and process nutrient-rich parts of bamboo that contain cyanide (poison). Being able to process toxins removes competition for that food resource as other species cannot consume such foods.
- Some individuals who migrated north evolved into the mongoose lemur, which inhabits the northwest forests on the island. They change their active behavior throughout the year, being more active at night during the dry season and more active in the daytime during cooler seasons.
By changing their diet, behavior, and/or location, what was originally a huge gene pool with a diverse number of different traits, has now become over 100 different subspecies with each population having its own gene pool containing a variety of different characteristics. Over time, genetic traits become more visible, which can be seen from the lemur phylogenetic tree below:
Genetic diversity is the foundation for evolution and species diversity. When combined with competition, and other species’ interactions, it can lead to the evolution of multiple new species and subspecies. Each one performs a role within its respective ecosystem to maintain its health and resilience.