Genetic and Aromatic Signatures in the Polemonium viscosum Complex

When you stop to smell the flowers, you’ll notice that many of them do not quite smell the same.

The Science Behind Floral Scents

There are biochemical reasons behind distinct scents. To discover them, we analyze the associated volatile organic compounds (VOCs) that are produced by plants. These combinations of molecules aid in attracting pollinators, deterring herbivores, preventing microorganism colonization and even enabling communication with other plants. Volatile organic compound composition can play a pivotal role in gene flow and can vary among populations due to differing selective pressures from local insect communities.

Polemonium (Polemoniaceae) is distributed primarily throughout the western United States and Canada, with few species found in South America, Asia and Europe. Within the genus, there is a group referred to as the Polemonium viscosum complex, consisting of three closely related, high elevation species: P. viscosum Nutt., P. confertum A. Gray and P. brandegeei Greene.

Untangling a Taxonomic Mystery

Polemonium viscosum is usually described as having a stronger "skunky" odor, while P. confertum is noted for its sweeter aromatics. The unique floral aromas make the complex ideal for investigating scent variation in alpine environments. However, taxonomy within this group is controversial and disagreement exists on the recognition of P. confertum apart from P. viscosum. This has serious implications on the insights into the role of floral scent divergence and species boundaries.

To explore the taxonomic confusion and floral scent profiles of the species within this genus, I have dedicated the last two years to collecting as much data as I can on them. I spent the summers of 2024 and 2025 collecting tissue and scent samples of the species throughout the Southern Rockies of Colorado and New Mexico.

Exploring Speciation in Alpine Wildflowers

By integrating floral scent analysis with statistics of genetic relatedness, this project aims to resolve species boundaries while also characterizing floral scent variation within the Polemonium viscosum complex. These wildflowers present a unique opportunity to explore floral scent variation and its role in speciation, with implications for conserving alpine plants.

Is speciation occurring in sympatry driven by divergence in floral scent profiles? Or is there a single species exhibiting two distinct floral scent profiles to optimize ecological opportunities in an alpine environment with limited pollination potential?

This article was contributed by graduate student Ash Kerber.