New carnivorous plant

Botanists at the University of Wisconsin–Madison and the University of British Columbia have discovered a new carnivorous plant in western North America. Triantha occidentalis makes its home in wetlands and bogs from Alaska to California and inland to Montana. In the summer, it shoots up tall flowering stems coated with sticky hairs that trap small insects like gnats and midges. The scientists discovered that the plant acquires more than half of its nitrogen by digesting these ensnared insects, a welcome treat in its nutrient-poor habitat. “What’s particularly unique about this carnivorous plant is that it traps insects near its insect-pollinated flowers,” says lead author Qianshi Lin, who was a doctoral student at UBC at the time of the study. “On the surface, this seems like a conflict between carnivory and pollination because you don’t want to kill the insects that are helping you reproduce.” However, the plant appears to be capable of sorting out friend from food. “We believe that Triantha occidentalis is able to do this because its glandular hairs are not very sticky, and can only entrap midges and other small insects, so that the much larger and stronger bees and butterflies that act as its pollinators are not captured,” says Tom Givnish, a UW–Madison professor of botany and co-author of the report. The discovery was led by Lin and Sean Graham of UBC, who collaborated with Givnish and Cecile Ané, a UW–Madison professor of botany and statistics. The researchers reported their findings in the Proceedings of the National Academy of Sciences.

Graham had previously led an analysis of Alismatales genomes when his team noticed that Triantha had lost a gene that is often missing in carnivores. Combined with its penchant for trapping insects and its proximity to other known carnivorous plants, Triantha looked like an excellent candidate for being the next carnivore in the plant kingdom. Triantha’s environment also seemed conducive to carnivory. The carnivorous lifestyle is so energy intensive for plants that plenty of water and light seem necessary to allow it to evolve. “Only in habitats in which nutrients and nutrients alone are limiting would you expect carnivory to be an advantage,” says Givnish. Insects can be excellent sources of nutrients the soil lacks, especially nitrogen and phosphorus. In field experiments, Lin fed Triantha with fruit flies labeled with the stable isotope nitrogen-15, which allowed him to track the nutrient as it entered the plant.

Source: University of Wisconsin–Madison