A common garden experiment to evaluate the morphological distinction between two species of shooting star (Primula section Dodecatheon) native to Pennsylvania

Two similar species of Primula section Dodecatheon are native and rare in Pennsylvania: P. meadia in the Potomac watershed and P. 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; 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, an...