Cladistic analysis of molecular data (plastid rbcL sequences) supports
the interpretation of simultaneous microsporogenesis as an apomorphy
for Asparagales (Lilianae), with a reversal in the most derived 'highe
r' asparagoid clade, which is entirely successive. 'Lower' asparagoids
are mainly simultaneous, with occasional reversals to the successive
state, such as in Xanthorrhoea, Hypoxidaceae, and a few Orchidaceae an
d Iridaceae (including Geosiris). Trichotomosulcate pollen, a characte
ristic feature of one of the lower asparagoid clades, is associated wi
th simultaneous microsporogenesis. Some lower asparagoids, such as Dor
yanthes and a few Iridaceae, are recorded as having both successive an
d simultaneous microsporogenesis. irregular tetrads occur frequently i
n Asphodelaceae and sometimes in higher asparagoids, although not in t
he group with trichotomosulcate pollen. We relate the distributions of
these characters to the positions of the same taxa in the rbcL tree,
expanded to include more taxa sampled for pollen characters. The polle
n data are highly congruent with the rbcL tree, although when viewed f
rom the perspective of all previous classifications, trichotomosulcate
pollen would be interpreted to have evolved several times. We interpr
et distribution of both simultaneous microsporogenesis and trichotomos
ulcate pollen with the DNA tree to be an indication of the reliability
of both for taxonomic revision of family limits.