Plant-Soil Interactions as a Potential Constraint on Asclepius Milkweed’s Ranges — 86a — Jordan Hastad, Dr. Carrie Olson-Manning, Dr. Paul Egland, Sneha Acharya, Gabriela Rabboni, Pedro da Racha Borin, Jack Erickson, and Jacob Mills

Asclepias speciosa and A. syriaca inhabit a variety of soil clines throughout the continental United States. These species converge along a precipitation gradient with the western A. speciosa generally inhabiting arid soils with less-developed horizons. In contrast, the eastern A. syriaca is exposed to higher moisture and soil types with greater nutrient content. Therefore, it seems likely that these plant-soil interactions could influence species’ ranges. Soil from Custer State Park, South Dakota (SD) (home range for A. speciosa), and soil from the Outdoor Campus of Sioux Falls, SD (home range for A. syriaca), was collected June of 2024. Then, in a greenhouse, both species were grown on both soil types to compare germination, plant height, and root establishment. Germination rates were 30% higher on Sioux Falls soil than Custer soil for both species. Furthermore, A. speciosa both germinated and established its roots sooner than A. syriaca by an average of 1 and 9 days, respectively. Although soil type had little effect on A. syriaca growth, A. speciosa performed better on the Custer soil growing, on average, 1 cm taller and taking 3 less days to establish roots. Altogether, we show that A. speciosa exhibits faster early growth–a trait conducive to increased survival in arid climates–and better performance on Custer soil. Our findings suggest that plant-soil interactions foster a home-soil advantage within A. speciosa and may partially explain the range limits for this species.

Augustana University
Dr. Steven Matzner