Using DNA to identify unique and related species is a powerful tool that has only recently become available to biologists. Just like DNA identification is being used to identify individuals involved in criminal activity by forensic scientists, biologists can use DNA to differentiate between different species in the environment.
In forensics, criminologists can differentiate by two different people by differences in their DNA sequences. A tool that can discriminate between human individuals can easily be used to tell species apart.
All individual organisms, which reproduce sexually, whether they’re humans, insects or plants, have unique DNA. Even those organisms that reproduce asexually will have differences in DNA between species, if not between individuals. By analyzing the DNA from the cells of an organism it is possible to identify how closely it is related to another organism.
Defining what an individual species is can be difficult. Generally it is considered that a species is a classification of organisms which are capable of successfully breeding and whose offspring are fertile. Other definitions might be a group of organisms that actually do breed regularly. This definition excludes populations that would be capable of breeding but don’t do so due to reasons such as geographic isolation.
Regardless of the definition used, DNA can tell how closely one population is related to another. Traditionally species were identified by morphological characteristics, or what they looked like. But, when we look at the dog, for example, it is clear that this is unreliable, at best. All dogs with which we are familiar, from the Chihuahua to the Great Dane are of the same species, and are a subspecies of the gray wolf.
And, the opposite problem can occur where due to mimicry or convergent evolution different species; even those from different biological families can appear the same. The monarch butterfly and the viceroy moth are one example of such mimicry. While the trained eye can tell the difference between a butterfly and a moth, on initial examination of morphological characteristics they are very similar.
DNA identification can show that all of the individuals of the domestic dogs with which we are familiar are closely related. While it is obvious that a Chihuahua cannot naturally breed with a Great Dane, due to physical differences, they are still the same species.
Determining the degree of biological separation between individuals is possible because DNA is inherited. In sexual reproduction half of the individual’s DNA comes from each parent. And, over time, minute changes, or mutations, creep into the DNA sequence. By measuring the differences due to mixing through sexual reproduction and knowing a general rate of mutation over time scientists are able to tell the degree of kinship between two individuals. It is even possible to calculate how far back in time different species diverged from a common ancestor.
Modern tools have made DNA species identification more and more powerful. Using a combination of electronic, optical and biological components it is now possible to measure the separation between species in a matter of minutes. For known species DNA chips can even identify hundreds of species simultaneously. And, even if a species is unknown, such technology can quickly rule out it’s belonging to an already known species.
While it is still necessary to make the decision of what constitutes a species, DNA is a very powerful tool in the effort to identify and differentiate between species. And with modern tools it is becoming ever easier to perform such identifications.