College of Agriculture & Natural Resources Department of Entomology

A recent study, published in Ecology, has provided comprehensive findings about the impact of plant chemistry on insect communities. This research, which features significant contributions from Dr. Andrea Glassmire, who conducted the study during her postdoctoral fellowship at Michigan State University’s Department of Entomology, offers a thorough examination of how specific chemical traits of neighboring plants influence herbivore and predator populations.

The study “The Frequency and Chemical Phenotype of Neighboring Plants Determine the Effects of Intraspecific Plant Diversity” tackles the challenge of understanding how intraspecific plant diversity influences ecological dynamics. Researchers explored how these variations affect insect interactions by focusing on plant neighborhoods with varying chemical traits.

Scientists have long recognized the influence of intraspecific diversity, the variation among individuals of the same species, on community patterns and species interactions in terrestrial and aquatic environments. However, deciphering the specific traits and mechanisms driving these effects has been challenging. Previous studies have often overlooked the role of chemical diversity, focusing instead on genetic diversity and its broader effects.

This study addresses a significant gap by manipulating chemical traits within plant neighborhoods using Solanum pennellii introgression lines. Researchers created 14 unique neighborhood treatments to explore variations in three key chemical classes—acyl sugars, proteinase inhibitors and terpenes. By assessing how these chemical variations affect herbivores and predators, the study provides new insights into the role of chemical diversity in plant–arthropod interactions.

The study’s results reveal that the diversity of specific chemical traits, rather than the total chemotypic diversity, is a crucial determinant of insect abundance on focal plants. Notably, diversity within individual chemical classes had distinct and often contrasting effects on herbivore and predator populations. For instance, neighborhoods with high levels of monoterpenes were linked to improved plant performance and a more diverse predator community.

The study also highlights the importance of insect mobility in response to plant chemicals. Flying and crawling insects responded differently to chemical cues, demonstrating that mobility affects how insects interact with plant defenses. Flying insects, which rely on indirect defenses such as airborne terpenes, and crawling insects, which interact with direct defenses like acyl sugars, exhibit distinct patterns of behavior based on their mobility.

These findings have significant implications for agricultural practices. The research suggests strategically selecting chemical traits in crop plantings could enhance pest management and promote sustainable farming practices. Farmers can optimize plant-insect interactions and improve crop health by maintaining a diverse range of chemical traits.

The study’s innovative approach, combining chemical manipulation with detailed insect sampling methods, clarifies how intraspecific chemical variation influences arthropod communities. It emphasizes the need for a nuanced approach to plant diversity in both natural and agricultural systems.

This study was supported by Agriculture and Food Research Initiative Competitive Grants from the U.S. Department of Agriculture National Institute of Food and Agriculture. 

Dr. Glassmire will return to MSU as an assistant professor and hold joint appointments in the Department of Entomology and the College of Natural Science Department of Plant Biology, effective January 2025.