Jack Hager
Fri, 17 Apr 2026 10:45:00 PDT

Using Herbarium Specimens to Morphologically Delineate Three Western Phlox Species

Jack Hager, Meredith Zettlemoyer

Western Phlox are incredibly ecologically diverse, found in a variety of habitats spanning deserts, sagebrush, and mountains. The genus contains around 65 unique species, often with overlapping trait variation that makes morphological delineation difficult. Phlox missoulensis is an endemic cushion plant species found only in the Missoula Valley; it occupies lower-elevation, windy, arid ridgelines that mimic alpine conditions. Two other Phlox species found nearby, Phlox kelseyi and Phlox pulvinata, occupy overlapping ecological niches. P. kelseyi is found in wetlands spanning from valleys to montane environments at similar elevations to P. missoulensis. P. pulvinata is found in subalpine environments more similar to the habitat where P. missoulensis persists. P. missoulensis appears to exhibit intermediate traits relative to these two potential sister species. For example, P. missoulensis has a more sprawling growth form than P. pulvinata, which exhibits the dome shape and dense canopy characteristic of alpine cushion plants, but P. missoulensis is more cushion-shaped than P. kelseyi. We use herbarium specimens and ImageJ software to quantify morphological trait variation of P. missoulensis and its sister species, including leaf width, leaf length, sepal length, and flowering time. I hypothesize that P. missoulensis will have intermediate leaf traits between the two sister species, including shorter, narrower leaves than P. kelseyi, yet longer, wider leaves and longer sepals than P. pulvinata. Additionally, I predict that P. missoulensis will have the earliest flowering time of the three species. This study will inform population sampling for a future genomic study and a conservation plan protecting P. missoulensis as a state species of concern. This study will be a stepping stone in uncovering the evolutionary relationships and history of Western Phlox.