Paleobotany in the Post-Genomics Era
Nixon, Kevin .
The land of molecular Oz: Armchair paleobotany and molecular clocks.
IN combination with the availability of DNA sequence data for extant taxa, an understanding of the value of simultaneous (“total evidence”) analysis of extant and extinct taxa, and the continued discovery of new and informative fossils, the potential of paleobotanical studies to shed light on long-standing evolutionary questions has increased exponentially in recent years. One consequence is our ability to apply minimum ages to divergence times of clades based on reasonably secure estimates of phylogenetic relationship combined with fossils that have been placed with cladistic methods. At the same time, some molecular biologists have resurrected the failed “molecular clock” approaches first developed in the 1960s and 1970s, with minor but unconvincing modifications, resulting in a plethora of new “estimates” of the ages of major clades. Unfortunately, these recent forays are usually based on one or a few, often poorly identified, not cladistically tested, and rarely re-examined fossils for calibration of model parameters. In some cases, when fossil ages have conflicted with minimum ages estimated on the basis of poor calibration and questionable models, authors have proposed rejecting the identity of the well-studied fossils. Regrettably, such unscientific “reasoning” seems to be gaining momentum, and threatens to marginalize rigorous scientific endeavors such as the study and placement of fossils based on combined cladistic analysis of both fossils and extant taxa (based on morphology and molecular data). This trend may ultimately result in the loss of knowledgeable paleobotanists in favor of molecular generalists who have only a superficial (at best) understanding of fossils, or the fossil record. Although this may seem unlikely to some, one need only look at the current state of plant taxonomy to see that such a scenario is not only possible, but likely.
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1 - Cornell University, Plant Biology, LH Bailey Hortorium, 228 Plant Science Building, Ithaca, New York, 14853, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 2:00 PM