Tennessee is astoundingly biodiverse. The number of species that are deemed rare or in need of conservation attests to that: in one form or another, close to fifteen hundred animals and over five hundred plants are deemed rare. The smaller the population, the more of a challenge it becomes to use traditional field methods to figure out what might be leading to the species’ demise. Luckily, there’s a particular subset of scientists (and their numbers are growing!) that can lend a helping hand. Conservation geneticists look to the DNA of rare populations to help shed light on why some species are struggling.
To understand how DNA can answer questions about rare species, it is first essential to understand genetic diversity. This refers to the number of different versions of a gene there are in a population. In a classic example from Genetics 101, a flower species has a gene that determines its color, but it might have different versions of that gene—one version makes the flower red, another white, and maybe yet another blue (these different versions are called alleles). A population with low genetic diversity means it has fewer versions of a gene. This also means that the individuals will have a lot, maybe even too much, in common. When they continue to breed, or inbreed, then the population becomes less fit to handle the challenges of life. For instance, if a disease sweeps through a population of flowers, and all of the flowers have the same weak disease-resistance gene, that doesn’t fare well for those red, white, and blue flowers. However, if there is more genetic diversity for that gene, then at least some of the flowers would hopefully be more genetically equipped to survive.
If low genetic diversity can lead to population collapse or the extinction of a species, then the insight provided by conservation geneticists can be a lifesaver. Consider the case of the Florida panther, a subspecies of cougar. A couple decades ago, there were only a couple dozen left in the wild, and they were riddled with heart diseases and birth defects. In a last-ditch effort to save the critically endangered population, a group of female cougars from Texas was introduced into the Florida panther population. Several years later, the study showed an increase in genetic diversity, and the population increased dramatically too.
One of the primary causes of the loss of genetic diversity in the Florida panthers is a common one for many rare species: habitat loss and fragmentation. While this can be a roadblock for all living things, it gets more complicated for our brethren in kingdom Plantae that lack the means to move themselves from one point to another (except by hitchhiking on an animal or the wind). Plants face all the same risks as isolated animal populations—they also experience genetic erosion (the loss of genetic diversity) from inbreeding and shrinking gene pools. However, things get more complicated with plants. For one, they can reproduce clonally. That is, instead of reproducing sexually and producing seeds, the plants will establish colonies via underground roots. In many cases, this is an adaptation that allows them to survive during times of stress. But clonal reproduction becomes an issue when the population is small and made up of the same genetic individual. This is compounded when a plant doesn’t have the ability to self-fertilize (also called selfing—a plant that can produce seed when the sex cells come from the same flower). In essence, it becomes a population of clones.
Determining whether a clump of stems is a colony of the same individual or multiple distinct plants presents a challenge for ecologists in the field. In fact, this has been an issue with a critically endangered sunflower, the whorled sunflower, here in Tennessee. With only two known populations that occur in small clumps, biologists who monitor the species are not sure whether they are counting unique individuals or clones that are all part of the same plant. They rely on conservation geneticists who can shed light not only on the genetic diversity but also on the growth patterns of the rare plant.
The conservation of our rare species is a true team effort. It requires dedicated field scientists who are willing to brave the snakes, mosquitos, ticks, brambles, and all manner of other obstacles to study species in their native habitat. It also requires the expertise of conservation geneticists who do much of their work in a lab. For all of us, the common goal is to conserve the unique biodiversity, of which genetic diversity is an integral part. So even though we’re in Tennessee where it’s common to make hillbilly inbreeding jokes, give some thought to our furry and photosynthetic brothers and sisters that wouldn’t appreciate that humor. After all, many of them are forced into that lifestyle because we’ve changed their habitat.
