Morphology and evolution of Arytera pollen (Sapindaceae-Cupanieae)

A description of Arytera pollen based on light and scanning electron microscopic observations is presented. Four aperture types and two ornamentation types (one divided into two subtypes) can be distinguished. The commonest aperture types are colporate and parasyncolporate; each of the other two types occurs in a single species. The main ornamentation types are rugulate and striate-rugulate; the latter has small or large lumina. Polymorphism occurs in both characters in several species. A cladistic analysis of Arytera shows two distinct evolutionary trends in the pollen: 1) aperture system from parasyncolporate to colporate, and 2) ornamentation from striate-rugulate with small lumina to striate-rugulate with large lumina. The plesiomorphic state of the character ornamentation remains uncertain. The result obtained contributes to the doubt whether primitively colporate pollen occurs within the subfamily Sapindoideae. In contrast to the general view of evolution in Sapindaceae pollen, the aperture system of Arytera pollen did not appear to be more conservative than the ornamentation. The evolutionary changes in the aperture system and ornamentation do not ‘coincide’, which suggests them to be functionally relatively independent.