Palynological variation in primula L. subgenus Sphondylia (Duby) Rupr., and the relationship of this group to Dionysia Fenzl.

summary Primula subgenus Sphondylia is composed of eight localized and probably relictual taxa distributed from Ethiopia to the west Himalaya. It is considered to occupy an ancestral position in the genus, and to demonstrate stages in the evolution of dimorphic heterostyly. Previous authors have suggested that the heterostylous genus Dionysia evolved from forerunners of this group. It has previously been reported that, in five of the species, only prolate 3‐colporoidate pollen is found, dimorphic in size for heterostylous species. However, the pollen of the heterostylous species P. edelbergii, P. gauheana and P. darisii is dimorphic for shape and colpus number, as well as for size. Thus, our study reports for the first time, a major morphological pollen dimorphism, and 1‐ and 2‐colpor(oid)ate pollen in the Primulaceae. We found that three distinct trends in the development of pollen dimorphism can be traced in this group, two of which appear to have no major phyletic implication. However, it is possible that P. floribunda represents phyletic links between subgenus Sphondylia and later heterostylous developments in Primula. Pollen in Dionysia is said to be weakly dimorphic for shape and colpus number, and our findings agree with this. We suggest that Dionysia is not closely related to Primula subgenus Sphondylia and that strong superficial resemblances between certain taxa in these groups may have resulted from parallel evolution.