Colloquium: The Utility of Pollen in Systematic and Morphological Studies: A Celebration of the Life of John J. Skvarla
Watson, Linda E. , Estes, James R. .
Systematic Utility of Pollen Characters in the Compositae Revisited: The Groundbreaking Studies of John J. Skvarla.
John J. Skvarla was a pioneer in the use of transmission and scanning electron microscopy in understanding the fine structure and external sculpturing of pollen walls and in the application of that data to understanding relationships within a broad array of plant families. His investigations of Compositae pollen with Billie Turner and others was groundbreaking. Ultrastructural traits of the exine were characterized and evaluated across the full range of variation providing a suite of characters not visible through light microscopy. Skvarla recognized four basic exine types (Helianthoid, Seneciod, Arctoid, and Anthemoid) for the family based on ultrastructural sections of the wall, and they were interpreted within a systematics framework. This was the first comparative study to use these features. Unfortunately, rigorous approaches to understanding the phylogeny of Asteraceae were not yet available. Therefore, the interpretation of pollen characters was hindered because of our misunderstanding of which tribes were ancestral and derived. With the advent of molecular systematics, our understanding of phylogenetic relationships for the Asteraceae were greatly clarified, and what were once considered basal members of the family were revealed to be the most derived. John Skvarla with Stephen Blackmore and others re-examined the original data and abandoned the four pollen types, and re-analyzed the data by optimizing individual pollen characters onto the molecular phylogenies for the family. This resulted in unparalleled insight into the evolution of pollen within Asteraceae and congruence with the current classification of the family. Thus Skvarla, who was the first to examine the pollen of Asteraceae in a comparative fashion with this new technology that he forged, was among the first to deconstruct pollen types and analyze individual characteristics within a phylogenetic framework. This places his work on the Asteraceae among the classic studies of the phylogenetic utility of pollen, two times over.
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1 - Miami University, Department of Botany, Oxford, Ohio, 45056, USA
2 - University of Oklahoma, Botany and Microbiology, 770 Van Vleet Oval, Norman, OK, 73019, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Fort Camp Lounge/Gage
Date: Tuesday, July 29th, 2008
Time: 3:30 PM