Understanding plant evolution: morphology to molecules
Rothwell, Gar W. , Nixon, Kevin .
Plant Fossils as blank slates and blank checks.
Fossils, once strictly the realm of paleobotanists and botanists, have achieved newfound glory as calibration points in numerous clonally reproducing molecular dating papers. As pointed out elsewhere as well as by others, serious issues still face such studies, even though the results are typically presented with great flair and confidence. In addition to a rather simplistic view of evolutionary rate, the underlying quality and identity of fossils used as calibration points should, but usually doesn't, reduce the credibility of such chronograms. That said, the most important aspect of any fossil (or morphological) study can be distilled to a single word: homology. By wishfully (or willfully) projecting complex and/or verificationist homology statements onto fossil features, almost any desired relationship can be achieved, especially when few characters are available. Examples of such verificationism are replete in the literature of the past few decades, such as construction of the "anthophytes" (and their recent resurrection) based on fanciful angiosperm ovule-seedfern cupule homologies, and the interpretation of missing organs as previously present by "reduction" (e.g., Archaefructus) thereby allowing completely unsupported interpretations (e.g., viewing isolated naked carpels or stamens as flowers, and flower like aggregations or carpels and pistils as inflorescences). It is odd that we allow any particular gene to be "incorrect" due to homoplasious character states, but we feel compelled to force all morphology to conform to our preconceived concepts of relationship - these often based on the molecular trees we seem to be attempting to verify.
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1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - Cornell University, Plant Biology, L. H. Bailey Hortorium, 412 Mann Library Building, Ithaca, NY, 14853, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Room 4/Woodward
Date: Monday, July 28th, 2008
Time: 2:45 PM