Yellow-eyed grasses may have more insect visitors than previously thought

University Park, Pa. – Scientists previously believed that a family of flowering plants called yellow-eyed grasses did not attract many insect visitors, but the recent discovery of a fungus that infects the plant and produces fungal „pseudoflowers” has researchers reconsidering this assumption.

In 2020, Scientists working in Guyana discovered Small fungal structures on the grasses that resemble the plant's natural blooms can add interest to the plant. Scientists theorize that fungi mimic fungi to attract fungi, which then pick up and spread fungal spores.

The theory prompted researchers to rethink the assumption that insects rarely visit plants: Why would a fungus try to mimic a plant's flowers if they didn't attract insects?

A new study published in Proceedings of the Entomological Society of Washington, A team led by Penn State researchers published the first documentation of arthropods visiting these grasses in the South American country of Guyana, where plant species are extremely diverse.

They found that a variety of arthropods visited these plants, including spiders, beetles and other insects such as grasshoppers, locusts and crickets. A gasbearing moth caterpillar called Coleophora was also seen visiting the plants.

Terri Torres-Cruz, a postdoctoral research assistant at Purdue University, led the study while earning her Ph.D. Plant pathology from Penn State College of Agricultural Sciences. He said the findings suggest that insects and other arthropods may visit these plants more frequently than previously believed.

„We were a little surprised to observe a variety of insects on these grasses and their flowers, which were thought not to produce nectar and attract many insect visitors,” Torres-Cruz said. „But most of what we know about insect visits to these plants comes from studies done in the United States, so conducting this study in Guyana led to new observations.”

Michael Skvarla, assistant research professor of arthropod identification at Penn State, said the results may also provide insight into how plants are pollinated.

„Yellow-eyed grasses have historically been thought to be wind-pollinated, so finding that they are visited by multiple species of insects opens up the possibility that they are actually insect-pollinated,” Skvarla said. „These plants are also found in Africa, Asia and Australia, so it would be good to confirm that insects also visit flowers on those continents.”

Although a few yellow-eye grass species are used as ornamentals in flower arrangements, as companion plants for carnivores, and as food for wild turkeys, they are generally of little economic or agricultural importance. But studying the grasses is important, the researchers said. One species of the plant — Xyris tennesseensis — is a federally endangered species in the United States, and many wetland plants are threatened by habitat loss worldwide. Learning more about how these plants pollinate and produce seeds can help conserve these species.

„Part of my work studying these plants was trying to determine if the insects had seen the flowers because there were no official reports for the species of interest,” Torres-Cruz said.

Additionally, according to the researchers, there are not many known fungal pseudoflower systems, so learning more about this system will allow scientists to compare it to other pseudoflower systems.

For this study, the researchers looked at vegetation at three sites in Guyana: the Demerara-Mahaika region, the Upper Demerara-Berbise region and the Potaro-Sibaruni region. They took photographs during observation periods and then used them to identify arthropods.

They found that about 15 to 20 arthropods visited the plants in each area per hour.

In the Demerara-Mahaica region, researchers observed long-jawed orb weavers, looper caterpillars and grassland katydids. In the Upper Demerara-Berbice region, they found bees and grassland katydids on plants. Finally, in the Potaro-Chibaruni region, the team found cases of orb-weaving spiders, lynx spiders, crab spiders, leaf beetles, stingless bees, meadow cadidids and cassier moth larvae in the grasses.

„The meadow katydid, belonging to the order Orthoptera, was the only insect found at all three sites,” said Torres-Cruz. „They were mostly seen feeding on the pollen and flower tissue of plants.”

In the future, more studies could examine whether yellow-eyed grasses on other continents are visited by insects, the researchers said. A planned follow-up study led by Torres-Cruz will compare insect visitation between flowers in grasses and fungal pseudoflowers in plants.

Lauren Ray, Evergreen State College; Jack Johnson, Northwest Mushroom Association; and David Keyser, professor of mycology at Penn State, worked on the research.

This research was supported by the US National Science Foundation, the Pennsylvania State Agricultural Experiment Station, the American Philosophical Society Lewis and Clark Fund for Field Research, and the Mycological Society of America.