Table 3.

Strengths of reproductive barriers between Primula elatior and Primula vulgaris for distribution (ecogeographic: RI_ecogeo), flowering (phenology of parents: RI_phenoP), pollen transfer (mechanical: RI_mech), F1 seedling formation (seed developmental isolation: RI_seedling), F1 survivorship (RI_survivorship), and F1 reproduction, subdivided into phenology (RI_phenoF1), flower production (RI_flower), seed set (RI_{seed set}), and male sterility (RI_male). The combined strength of individual barriers is presented for all premating barriers (RI_pre), all postmating barriers (RI_post), all pre‐ and postmating barriers (RI_tot), and all barriers occurring under sympatry (RI_sympatry). RI‐values range from one (complete isolation: no interspecific gene flow) through zero (no isolation: equal probability of intra‐ and interspecific gene flow) to minus one (no isolation: all gene flow is interspecific; Sobel and Chen 2014)

	Stages in life cycle	Barrier name	P. elatior		P. vulgaris
			L‐morph	S‐morph	L‐morph	S‐morph
Premating	Distribution	RIecogeo	0.827		0.590
	Flowering	RIphenoP	0.237		0.417
	Pollen transfer	RImech a	0.100	−0.273	0.158	−0.136
Postmating	Formation of F1 hybrids	RIseedling a	0.282	0.184	0.789	0.393
	Survivorship of F1 hybrids	RIsurvivorship b	0.054		−0.097
	Reproduction of F1 hybrids	RIphenoF1 b	−0.046		−0.136
		RIflower b	−0.125		−0.194
		RIseed set a , b	−0.116	0.092	0.223	0.317
		RImale a , b	−0.088	−0.123	0.378	0.008
Total	Premating	RIpre a	0.881	0.812	0.799	0.728
	Postmating	RIpost a	−0.034	0.036	0.851	0.311
	Pre‐ and postmating	RItot a	0.873	0.843	0.982	0.847
	Pre‐ and postmating without RIecogeo	RIsympatry a	0.283	0.065	0.949	0.587

L, long styled and S, short styled.

^aRI was calculated separately for long‐ and short‐styled morphs, using the pollen‐receiving morph as reference.

^bAverages across RI‐values of the two F1 hybrid classes (EL^♀ × VU^♂ and VU^♀ × EL^♂ hybrids; see Figures S5–S9).