Wherever two or more different species of narcissus grow together, there is a posiibilty of natural hybrids being produced. However even if the species populations are large natural hybrids may not be freely produced. This may be due to incompatability between the chromosomes of the two species or because both species are not visited by the same insect pollinator. Narcissus cyclamineus in north-western Spain and Portugal is commonly found growing with N. bulbocodium subsp. bulbocodium yet only one hybrid has ever been found and that not until 2005. The paper describing the hybrid N. × caramulensis found in the Caramulo mountains in central Portugal can be viewed/downloaded here.
Section ganymedes with other sections are included in an article published by the daffodil society which can by accessed by clicking here