An Introduction to Introductions
Author: Aaron David, Ph.D.
Endangered species are those that are at risk of extinction. Often, these species are designated as endangered because there are either very few individuals left in the wild or, more commonly for plants in our region, very few populations (groups of these species usually within a larger site) of these species in the wild. For these rarest of these rare species, the remedy to prevent extinction is typically adding more individuals within a population and/or more populations. To prevent extinction, conservationists use ‘introductions’ to create new populations on land within the known range of the species, and ‘augmentations’ to bolster existing populations in the wild.
Introductions in particular are most useful for species that have very few populations. For example, introductions of rare plant species on the Lake Wales Ridge include those for Garrett’s Mint (Dicerandra christmanii), Avon Park Harebells (Crotalaria avonensis), and Florida Ziziphus (Pseudoziziphus celata), each of which is known from only a handful of properties. Each population that conservationists introduce to the wild is incredibly important for allowing the species to persist into the future, and acts a bit like insurance against a catastrophic event.
The planning stages of any introduction are crucial for success. The first step is determining where the introduction should take place. Conservationists select sites that have the appropriate habitat and soil for the endangered plant, as well as a high likelihood of persisting in the future. For that reason, public lands owned and managed by the state or federal government or private, conservation-oriented properties are often selected. In Highlands County, many of the Florida Fish and Wildlife Conservation Commission (FWC) Wildlife and Environmental Area tracts as well as the federally owned Lake Wales Ridge National Wildlife Refuge are utilized for introductions because of the long-term protection they offer.
Next is determining where the source plant material, called “propagules”, will come from. Propagules may be seeds of the endangered plant, or whole plants grown from seeds or stem cuttings. In some cases, horticulturalists may even use tissue culture to generate whole plants from a few growing cells in a laboratory! Even more important than the propagule type is the origin of those propagules. Many times, an introduction is done to save a particular population and its unique genes from dying out. For example, many of our native scrub species persist on private, undeveloped lots. Conservationists may rescue propagules from this ‘source’ population and use them for the new introduced population.
As the date for the introduction draws near, conservationists and land managers work together prepping the site for the introduction. Here in Highlands County, this often means conducting a controlled burn at the site to clear away overgrown shrubs, though may also include removal of exotic species that could compete for nutrients and light with the endangered plant. Specific planting or seed sowing locations are selected to maximize success. However, because the best practices for a particular species are not always known, conservationists will also use an experimental approach in which they try different methods to not only increase the chances of the introduction working but also to learn about how to be successful in future introductions. Additional measures such as installing drip lines or encircling plants with wire mesh cages for protection against herbivores are often taken to help the plants succeed.
Finally, with the propagules ready and the site prepped, it’s time for the introduction. This part is by far the most fun and rewarding part of the process, and often a great time to invite other conservations and volunteers to help out. A typical introduction day is spent placing the plants or sowing seeds in the ground, turning on drip lines if necessary, and installing any anti herbivore cages.
Caption: Former Vaughn-Jordan Plant Ecology Research Intern Ella Segal inspects a transplanted Titusville Mint.
Though the work isn’t finished once the plants are introduced. Post-introduction monitoring is critical for a number of reasons. According to Dr. Aaron David, Archbold Plant Ecology Program Director, “By carefully monitoring the success of introductions, we can learn what went right or wrong, and improve. Importantly, we can also determine what work remains to be done to save the species.” The goal is to create healthy, self-sustaining populations that will keep the species going long into the future.
Introductions are a key action that conservationists take to save endangered species. Dozens of introduction here in Highlands County and on the Lake Wales Ridge have helped secure the future of several of our plant species found here and nowhere else. Stay tuned for another article about plant introductions.
Main Photo Caption: Dr. Aaron David, Archbold Plant Ecology Program Director, carries potted Florida Ziziphus plants to their new home as part of a recent introduction.