The unusual occurrence of tricolpate pollen within Mutisieae (Asteraceae)

Abstract

The monotypic genus Hecastocleis and species of Ainsliaea DC. (Asteraceae, Mutisieae) have tricolpate pollen, which is unusual in Asteraceae. The pollen morphology of H. shockleyi and species of Ainsliaea were studied with light microscope and scanning electron microscope. Pollen of H. shockleyi and some species of Ainsliaea have tricolpate aperture but differ in size and exine features. The pollen of Ainsliaea is bigger than that of Hecastocleis, and has more conspicuous microspines, a Mutisia- or an Ainsliaea-exine type, and is slightly thickened at the poles. The pollen of H. shockleyi is scabrate-microechinate with small puncta, and has the Mutisia-exine type, which is regularly thickened over the complete grain. The occurrence of tricolpate pollen supports previous studies that Hecastocleis and Ainsliaea stand apart from other genera of Mutisieae, but the occurrence of Mutisia-exine type does not suggest complete independence of the tribe. © 2005 Taylor & Francis.