from these three other similar species by being the only very sticky species, being completely covered in relatively long, yellowish, glandular hairs. It is also the only species in which the leaves in the middle of the rosette are clearly decurrent. D. minor, an endemic of the Balearic Islands, is not sympatric with D. thapsi. Distribution Digitalis thapsi is an endemic species of the Iberian Peninsula, occurring in both Portugal and Spain. It grows in the mountains and rocky plains of the central and central-western parts of the Iberian Peninsula, especially in the Sistema Central and its extensions between the rivers of the Douro and Tagus. It is widespread in Spain, occurring in the western and central parts of the country. It does not occur on the Balearic Islands. It occurs in the provinces of Ávila, Badajoz, Cáceres, Córdoba, Guadalajara, Madrid, Salamanca, Segovia, Soria, Toledo and Zamora. It has incidentally been found in the province of Burgos. In Andalucía it is only found in the north of the region, in the western Sierra Morena, where it is uncommon; it has been collected more often in the mountains of central Spain. In Portugal it primarily occurs in the northern and central interior, more precisely in the districts of Bragança, Vila Real, Guarda, Viseu, Castelo Branco, Portalegre and Évora. With less frequency, it has also been found in the Porto, Aveiro, Coimbra, Santarém, Beja and Faro Districts. Ecology Digitalis thapsi grows in acidic soils. It grows on rocky ground and on slopes. It prefers sunny, open and disturbed places. It generally grows on soils derived from granite, but also sometimes on quartzite and schist. It grows at (rarely 100-) 500-1500 metres in altitude. The specific phytosociological suballiance and alliance wherein it occurs is called 'Rumici indurati-Dianthion lusitani', which is in the order 'Phagnalo saxatilis-Rumicetalia indurati', in the class 'Phagnalo saxatilis-Rumicetea indurati'. It is a characteristic species of this phytocoenosis. In this habitat it occurs together with these following characteristic species: Antirrhinum graniticum subsp. graniticum, Antirrhinum rupestris, Arrhenatherum fernandesii, Biscutella bilbilitana, Centaurea monticola subsp. citricolor, Centaurea pinnata, Coincya leptocarpa, Coincya longirostra, Coincya pseudoerucastrum subsp. pseudoerucastrum, Coincya rupestris, Conopodium bunioides subsp. aranii, Conopodium majus subsp. marizianum, Crepis oporinoides, Dianthus crassipes subsp. crassipes, Dianthus crassipes subsp. sereneanus, Dianthus lusitanus, Digitalis mariana (both subspecies), Digitalis purpurea subsp. toletana, Erodium mouretti, Erysimum linifolium subsp. lagascae, Festuca duriotagana, Jasione sessiliflora subsp. tomentosa, Scrophularia oxyrhincha, Scrophularia sublyrata, Sedum hirsutum