Figure 2.- A) Geographic distribution of 22 populations of Primula vulgaris from Somerset, England. Pie charts represent intra-population frequencies of long-styled (L; white), short-styled (S; black) and homostylous (H; grey) floral morphs; dimorphic (D) populations consist of L- and S-individuals, except for population D*11, which consists of L- and H-individuals; trimorphic (T) populations consist of L-, S- and H-individuals; the single monomorphic (M) population consists of H-individuals. B) Ternary plot representing the frequencies of S-, L- and H-individuals sampled from the same 22 populations. Each vertex of the triangle represents complete population monomorphy for each floral morph; each side of the triangle represents different levels of population dimorphism (bottom: H-morph absent, only L- and S-morphs; left side: S-morph absent, only L- and H-morphs; right side: L-morph absent, only S- and H-morphs); each point inside the triangle represents trimorphic populations; arrow pointing to the base of the triangle represents equal frequencies of S- and L- morphs (i.e., isoplethy); the black dashed line represents the trajectory from isoplethy in distylous populations to complete homostyly observed in the sampled populations; the leftward shift of the line is caused by the greater reduction of S- than L-individuals; the grey dashed line represents the trajectory from isoplethy in distylous populations to complete homostyly with equal reduction of S- vs. L-individuals.