Pinguiculas of the Southeastern U.S.

Carnivorous plants are arguably some of the most charismatic of the natural world. Prevalent in popular culture and showcasing incredible diversity around the world, they are a botanical oddity that attracts attention. However, most people are more familiar with carnivorous plants like Venus Fly Traps and Pitcher Plants than they are with Pinguiculas, commonly called Butterworts. Pinguicula means “little greasy one” in Latin, named for the sticky exudate on the surface of the vibrantly colored leaves. This sticky glue produced at the tip of glandular hairs act as a trap for any small insects crossing its path. Glands then produce acids and enzymes to break down and "digest" it's prey (1). This evolutionary strategy has helped carnivorous plants persist in nutrient-poor environments around the world.  

The Molano-Flores lab's research focuses on plant-insect interactions and rare plant species, primarily, those that are state or federally listed. The three Pinguicula species we focus on range from fairly widespread to narrow-ranged endemics, however, all are on the threatened or endangered species list. This past February, we traveled down to the Florida panhandle to assess population size of three species, Pinguicula lutea, Pinguicula ionantha, and Pinguicula planifolia. These population counts help to inform the status of the species in the region, but also guide us in selecting populations for seed collection this upcoming Spring. These seeds will be used for seed germination studies in collaboration with the U.S. Fish and Wildlife Service. These studies help to inform conservation strategies for each species. 

Researchers Dr. Brenda Molano-Flores, Dr. Janice Coons, former graduate students Jenna Annis and Samantha Primer, and volunteers have worked together on a variety of studies with these species, focusing mainly on the reproductive ecology of these unique plants. All species can be found in slightly different habitats. Pinguicula planifolia, for example, likes to get its feet wet and is commonly found completely inundated, while Pinguicula lutea prefers drier upland sites. Microhabitat differences in the landscape can also affect the availability of prey like Collembola, Diptera, and other arthropods and prey capture is typically lower in dense grassy habitats compared to maintained habitats like right-of-ways that are intermittently mowed, and woody areas encroached with shrubby vegetation (4).

Another question one might ask about these predatory plants is, how do they avoid eating their pollinators? Fortunately, in the Southeastern U.S. flowers are most commonly pollinated by Hymenoptera (i.e., bees) and flowers are far away from the leaves too, preventing any pollinator-prey conflict.  Of interest, is that even though fruit and seed set are high, pollination events are generally less common (3). Research shows that dispersal limitation may be the biggest influence on carnivorous plant distributions (2).

Flower variation and leaf coloration and shape are a sure-fire way to tell these species apart. however, some species, like Pinguicula planifolia, change leaf color based on their growing conditions. Research by Annis et al. has shown that this change in pigmentation is a function of fluctuation in anthocyanin production (5). While this color change may not impact its ability to capture prey, it may play an important role in protecting the leaves from damage in sunny exposed areas. These studies play an important role in understanding the ecology of these species of Pinguicula, but also they show how cool these carnivorous plants are. 

Further Reading:

1 D'Amato, P. (2013) The Savage Garden: Cultivating Carnivorous Plants. Ten Speed Press.

2 Ellison, A.M. & Adamec, L. (2018) Carnivorous Plants: Physiology, Ecology, and Evolution. Oxford University Press. 

3 Molano-Flores, B., Primer, S., Annis, J., Feist, M. A., Coons, J., & Digges, R. (2018). Reproductive ecology of three rare North American Pinguicula species. Plant Species Biology, 33 (2), 129-139. https://doi.org/10.1111/1442-1984.12204

4 Primer, S.*, B. Molano-Flores, D.N. Zaya, C. Helm, and J. Coons. 2018. Effect of habitat structure on reproduction and prey capture of a rare carnivorous plant, Pinguicula lutea.  Arthropod-Plant Interactions 12:671-683.

5 Annis, J.*, J. Coons, C. Helm, and B. Molano-Flores. 2018. The role of red leaf coloration in prey capture for Pinguicula planifolia. Southeastern Naturalist 17:433-437.