In situ pollen diversity in the relict conifer Wollemia nobilis

Abstract

Pollen of the rare endemic Australian conifer Wollemia nobilis (Araucariaceae) has been reported to have quite variable features and has been linked to the dispersed fossil pollen Dilwynites. It was suggested that Dilwynites could indicate the presence of Wollemia in the fossil record since the macrofossil record for Wollemia is difficult to distinguish from the other Araucariacean conifers Agathis and Araucaria, as the characters appear intermediate between these genera. Here we describe in situ Wollemia pollen, prepared under different treatments to document those potential effects on the pollen morphology, using both light and scanning electron microscopy. We show that the pollen is more variable in size and surface texture than previously reported. We document variability of the intine thickness and show that it varies in different places across the grain. We did not detect previously reported layering of the wall, but do confirm the presence of Ubisch bodies and ‘bald areas’ on the pollen surface. This wider range of morphological variation strengthens the suggestion that Dilwynites pollen does not only represent Wollemia in the fossil record, but possibly also other members of the Araucariaceae.