Bell Museum Herbarium Sets Researchers on Path to Sundew Parentage

Tromp through a northern Minnesota bog, and you will likely find pitcher plants, featuring that ubiquitous vessel of insect demise. What you may miss is the state’s less showy vegetative carnivores: sundew plants. Often no larger than a teacup, sundew plants are covered in sticky “dew.” Insects trapped by the dew are digested by the plant, providing valuable sustenance in a nutrient-poor habitat. Minnesota is home to four sundew species, and thanks to genetic analyses, it turns out those species have an ancient history.

Making sundew discoveries was Dr. Ya Yang, the Bell Museum’s Curator of Plants, alongside her (now former) student Rebekah Mohn, a recipient of several Bell Museum fellowships. 

“She was my first student here,” Yang recalled. “Rebekah pretty much had to do everything from scratch… she’s driving this whole thing.”

Rebekah Mohn searches for sundew plants amongst the peatmoss of a northern Minnesota fen.

Doing everything meant leading field trips but also setting up a carnivorous plant nursery, as well as an insect nursery from which they could feed the plants. Space for that venture was found in the College of Biological Sciences Conservatory, where many of Mohn’s plants are still on view.

To find sundews in the wild, Mohn and Yang looked to the herbarium, the Bell Museum’s permanent collection of around one million plant specimens. Poring over location records, the researchers figured out where they would be able to go to relocate these tiny, sticky plants. Wading through bogs to collect around forty sundews gave them a good sample to run some genetic testing.

The white flower and carnivorous leaves of Drosera linearis, a native sundew.

That testing turned up some interesting results. It turns out that one of the most widespread of sundew plants, Drosera anglica, is actually the product of ancient hybridization between two other sundews: Drosera rotundifolia and the more localized Drosera linearis. These sundews buck the normal evolutionary trend of species splitting further apart over time. Something about the reconnection of two branches on the tree of life gives Drosera anglica, the ancient hybrid, an edge over the competition. Scientists still have to figure out exactly what that advantage is. A good place to start on thorny—or sticky—questions? The Bell Museum’s herbarium.

In Yang’s words: “The herbarium is permanent. Once we finish our work, the specimen we call a voucher specimen is a permanent record associated with the [genetic] sequencing work we’ve done. So in the future, if the plant name changes, if someone has any doubts about our work, they can check our specimen; it’s real and we did all the work.”