(Vol. 03, 2000-12) Phylogenetic Implications of Pollen Morphology and Ultrastructure in the Barnadesioideae (Asteraceae)
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The subfamily Barnadesioideae of the Asteraceae consists of nine genera and approximately 90 species. Both molecular and morphological phylogenies indicate that this subfamily is sister to the rest of the family. We have used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study pollen of 41 species from all genera of the Barnadesioideae. Three general pollen types are described in the subfamily: Barnadesia-type (Barnadesia, Huarpea), Chuquiraga- type (Chuquiraga, Doniophyton, Duseniella, Fulcaldea) and Dasyphyllum-type (Dasyphyllum and Schlechtendalia). A fourth type, Arnaldoa-type, consisting solely of Arnaldoa, is intermediate between the Chuquiraga- and Dasyphyllum-types. These types parallel and confirm findings from previous studies. Psilolophate grains are found only in the Barnadesia-type. Pollen with a cavity (cavea) between pollen wall units in each of the three interapertural regions is present in Barnadesia (Barnadesiatype), Dasyphyllum (Dasyphyllum-type) and Arnaldoa (Arnaldoa-type). The Chuquiraga-type does not have cavate pollen. Intercolpar concavities occur only in the Dasyphyllum- and Arnaldoa-types. In the latter, intercolpar regions are accompanied by pairs of indentations flanking the colpi. The presence of intercolpar concavities in Dasyphyllum and Schlechtendalia, often cited as a synapomorphy for the Barnadesioideae and Calycedceae, has apparently evolved independently within the subfamily. Chuquiraga pollen exhibits the least derived palynological features in the subfamily. Palynological characters, when placed in the context of current phylogenies for the Barnadesioideae, suggest additional phylogenetic analyses are needed to re-evaluate intergeneric relationships within the subfamily.