2 UNUSUAL POLLEN TYPES IN THE GENUS ARIST EA (IRIDACEAE-NIVENIOIDEAE)- PHYLOGENETIC IMPLICATIONS

The genus Aristea, with about 50 species, is the largest of the six ge nera of the subfamily Nivenioideae and is remarkably diverse in pollen aperture variation. Two unusual pollen types, trisulcate and dizonasu lculate, are recognized for the first time in the family. Both have be en studied by scanning and transmission electron microscopy. A prelimi nary cladistic analysis indicates that they belong to two independent lines derived from the monosulcate basic type. The distribution of the pollen characters of Aristea, correlates with fruit and seed characte rs and suggests that the genus originated in the Cape Region, where it diversified into three lines. A fourth line (represented by Aristea s chizolaena) radiated from eastern South Africa towards tropical Africa and Madagascar.