In August, the Rare Plant Conservation Program said farewell to over 200 Titusville balm (Dicerandra thinicola) plants that had been carefully propagated in the greenhouse over the past several months, as they were picked up by Hannah Bowen of Archbold Biological Station. The propagation work done at the Gardens was part of a project led by Archbold to introduce new populations of Titusville balm onto protected lands. The Titusville balm is one of 13 scrub mint species endemic to Florida, eight of which are listed as endangered. During the Pleistocene ice age, the Florida peninsula expanded to twice its current size, then reduced to a series of islands once the ice melted. According to the Florida Museum of Natural History, the glaciers arose and retreated a total of 17 times, leading to the radiation and genetic isolation of species, and divergence of a great diversity of unique plants, including the Florida mints. These species have adapted over millennia to grow in specific, limited regions of Florida and on specific habitat types.
Conserving Florida’s endemic mint species requires careful consideration of all of their habitat requirements and adaptations. For instance, establishing a new population, such as the one being established for Titusville balm by Archbold Biological Station, requires that the new site have the right vegetative community, contain the suitable soil series, be on the appropriate ridge system, and be located within the historical range of the species. More importantly, responsible conservation requires taking into account a species’ vulnerabilities as well. One major vulnerability for Florida mints is due to each of the peninsular species being allopatric, meaning that their historical ranges do not overlap with other mint species in their genus.
Research has demonstrated that when artificially grown in proximity to each other, the different mint species readily hybridize – they all flower at roughly the same time of year, and pollinators can easily transport pollen from one species to another. The seeds that are formed from these cross-pollinations form hybrid plants that are not fully either parent species, and which are not found in nature. Therefore, when an introduction site is selected, it requires a location that is not within pollination distance from a different mint species. If cross pollination were allowed to affect wild populations, just one event could genetically wipe out an entire species.
The Rare Plant Conservation Program has participated in introduction projects of several of the endemic, endangered Florida mint species over the past four decades. The process of reviewing and addressing each the species needs and vulnerabilities is the first and most important step required before any propagation takes place, so that each of the mint species can be responsibly preserved for the long-term and thrive protected in the wild for posterity to enjoy.
Blog post by Cheryl Peterson, Rare Plant Conservation Manager at Bok Tower Gardens.