WEBSTER, GRADY L.* and KEVIN J. CARPENTER. Sect. of Evolution and Ecology, University of California, Davis CA 95616. - Pollen morphological characters as phylogenetic markers in neotropical taxa of Phyllanthus (Euphorbiaceae).
Webster, Grady L., & Kevin J. Carpenter. Section of Evolution and
Ecology, University of California, Davis. Pollen morphological
characters as phylogenetic markers in neotropical taxa of
Phyllanthus (Euphorbiaceae). Over 800 species of
Phyllanthus have been classified into 10 subgenera with over 30
sections, but the broad scope of variation has made it difficult to
define monophyletic groups. Pollen morphological studies have provided
clues to phylogenetic relationships, but have dealt mainly with Old
World taxa. In the present study, pollen morphology has been
illustrated (using SEM) of 22 American species in 11 sections. Pollen
in subgenus Conami is of special interest because of reductions
of apertures and exine ornamentation (pilate in most species). In
subgenus Xylophylla, the spectacular development of clypeate
grains (with exine shields defined by distinct muri) provides the most
useful synapomorphy for defining this group of 80 species. An even
more remarkable occurrence of clypeate pollen, with very small exine
shields, occurs in section Cyclanthera; it remains unclear
whether this indicates a common origin with subgenus
Xylophylla. .
Key words: Euphorbiaceae, exine shields, neotropical, Phyllanthus, pollen morphology