Colloquium: The Utility of Pollen in Systematic and Morphological Studies: A Celebration of the Life of John J. Skvarla
DeVore, Melanie L. , Skvarla, John J. .
Revisiting intercolpar concavities within Calyceraceae and Subfamily Barnadesioideae (Asteraceae).
The presence of intercolpar concavities (IC) has been suggested to be a synapomorphy uniting Calyceraceae and Subfamily Barnadesioideae (Asteraceae). Addressing whether ICs within Calyceraceae and Barnadesioideae are indeed homologous has never been fully discussed. In Calyceraceae, ICs are found in association with ektexine bridges and colpar ledges, however, both of these features are absent within Barnadesioideae. The combination of these three pollen features (ICs, ektexine bridges and colpar ledges) is present within the Boraginaceae. Examination at the ultrastructural level indicates that taxa with ICs within Boraginaceae and Calyeraceae have foot layers becoming dome-shaped and thickest at the center of the meridional ridges. In contrast, there are two different ultrastructural patterns of meridional ridges within Barnadesioideae. Meridional ridges present in grains of Schlechtendalia consists of columellae with slight levels of internal tecta. In contrast, Dasyphyllum grains have meridional ridges that are caveate with columellae characterized with complex bases. It is conceivable that the meridional ridges present within Dasyphyllum are derived from a condition similar to that present within Schlechtendalia. There is not a compelling case for the ultrastructure of ICs within Barnadesioideae being derived from the condition present within Calyceraceae. In general, the exine of Calyceraceae pollen has thickened columellae that do not extend through the entire exine and that lack internal tecta. This is not the case within Barnadesioideae where the columellae do extend through the entire exine and internal tecta are present. The close ultrastructural resemblance between grains with ICs within Boraginaceae and Calyceraceae likely reflects the biomechanical constraints of the presence of the colpar ledges and ektexine bridges. It appears that ICs evolved separately within the Calyceraceae and Barnadesioideae.
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1 - Georgia College & State University, Biological & Environmental Sciences, 135 Herty Hall, Campus Box 81, Milledgeville, Georgia, 31061, USA
2 - University of Oklahoma, Department of Botany and Microbiology, Norman, OK, 73019, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Fort Camp Lounge/Gage
Date: Tuesday, July 29th, 2008
Time: 4:30 PM