Pollen Morphology in the Subtribe Metrosiderinae of the Leptospermoideae (Myrtaceae) and Its Taxonomic Significance.

Abstract

The pollen morphology of 28 species from the subtribe Metrosiderinae (s.Bentham) is described and compared in the light of several recent taxonomic revisions of this subtribe. All species have the same basic Myrtaceous pollen type, but there is intra and interspecific variability seen in a number of the pollen characters. Intraspecific variability is related either to changes in volume and size of the pollen grain or to the occurrence of polar islands. It is concluded that the character of syncolpy or parasyncolpy as relating to the presence or absence of polar islands may not be taxonomically reliable at the species level. Interspecific variation. and thus those characters most useful in assessing the taxonomy, relate to the structure of the angle of the amb, the exine structure and sculpture and the definition, form and type of colpi and apocolpia. One species shows a difference in polarity from the rest. Three basic exine sculpture types were defined, but it was necessary to examine them under the scanning electron microscope (SEM) because their patterns could not be resolved under the light microscope. Acetolysis enhanced the definition of the smaller basic sculptures under the SEM. Generally, the pollen morphology of these species was found to support the recent taxonomic revisions of this subtribe.