A Common Garden Experiment to Evaluate the Morphological Distinction between Two Species of Shooting Star (Primula section Dodecatheon) Native to Pennsylvania


Carol Loeffler

Additional Authors:

Larry Klotz


Sept 2018


Common garden, Dodecatheon, Pennsylvania, Primula fassettii, Primula meadia.

Two similar species of Primula section Dodecatheon are native and rare in Pennsylvania: Primula meadia in the Potomac watershed and Primula fassettii (syn. D. amethystinum), in the Susquehanna watershed. In the field, P. meadia is more robust than P. fassettii in most features. We conducted a common garden experiment to determine whether P. fassettii would more nearly resemble P. meadia. We collected seeds from one field site in both watersheds in 2008. Plants were grown in a greenhouse at Mt. Cuba Center, Delaware, until 2011, then in raised beds in a shade house. The first plants bloomed in 2012, and almost all bloomed in 2013 and 2014. We gathered data on 22 characteristics through 2014. The two populations exhibited statistically significant convergence in the common garden (less difference than in the field) in leaf length and length-width ratio, flower number, and capsule wall thickness. Significant divergence (more difference than in the field) occurred in scape diameter, corolla color, and capsule shape and color value. The remaining characters did not converge or diverge: leaf width, leaf base coloration, scape length, calyx lobe length, corolla length, calyx:corolla length ratio, anther length, and anther color, as well as capsule length, width, length-width ratio, valve length, hue, and chroma. In common garden (compared to field) scape dimensions, flower number, capsule dimensions, and capsule wall thickness increased while calyx lobe length decreased. Corolla and anther length did not change. Corolla color was significantly darker in Susquehanna plants, while capsule hue became more reddish in both populations.