Fitness components of the hybrid Phlomis x margaritae Aparicio & Silvestre (Lamiaceae)

Studies of microsporogenesis, pollen germination, pollen stainability, fruit and seed set and ovary predation have been undertaken to evaluate the fitness of the hybrid genotype of Phlomis x margaritae relative to its parents (P. purpurea and P. x composita) and allied taxa (P. x composita nothom. composita, P. x composita nothom, trullenquei, and P. lychnitis). Phlomis x margaritae shows irregular meiosis with very low pollen germination rate and very high pollen sterility, no seed set, and very high ovary predation. It thus has very low reproductive success and fitness. Phlomis x composita nothom. trullenquei also shows low pollen germination and seed set, but these follow regular microsporogenesis. The existence of cryptic structural sterility is suggested for this taxon. The rest of the studied taxa (P. purpurea, P. lychnitis and P. x composita nothom. composita) were fertile and can support the specific or subspecific taxonomic status of P. x composita. A feted ovule abortion pattern in the taxa with yellow flowers was found, since 'brood size' consisted just of one seed per fruit. On the contrary, P. purpurea was found to produce from one to four seeds per fruit. Some conservation implications are suggested. (C) 1997 The Linnean Society of London.