The study population grows along two parallel roads running East-West close to Ribès in the Spanish Pyrenees . The ’lower’ road is at 1150-1200m, whilst the ’upper’ road climbs 1250-1500m, and is 500-1000m north of the lower road. Hybrids are mostly confined to a ~1km ’core’ hybrid zone, with A. m. striatum - andA. m. pseudomajus -like plants becoming dominant to the West and East respectively  (Figure 1 ). We surveyed as many flowering plants as we could find in June and July of 2012 (n=2128), and collected information on flower number and location using a Trimble GeoXT datalogger. Antirrhinum grows in disturbed habitat such as roadsides and railways and much of the habitat between the two roads is forest and pasture, so it is likely that we sampled most of the plants that flowered. A. majus has a sporophytic self-incompatibility system, and self-pollinated seeds are very rare.