Paleobotany in the Post-Genomics Era
Hermsen, E. J. , Hendricks, J. R. .
Contributions of fossil taxa to understanding morphological character evolution.
INCREASINGLY, fossil taxa are being included in phylogenetic analyses, either through inclusion as terminals in morphological or simultaneous analyses, or using a “molecular scaffold” approach. While some of the interest in including fossil taxa in a phylogenetic framework may be due to targeted investigations of the fossils themselves, at least some interest may be due to recognition of the unique contributions that fossil taxa can make to our understanding of macroevolution. Fossil taxa provide at least two unique types of information to systematic studies: direct evidence of the sequence of evolutionary events and indication of the timing of those events. These unique attributes can make fossils particularly suitable for parsing the sequence and timing of morphological character evolution in a phylogenetic framework. In exploring the sequence of character evolution, fossil taxa provide direct evidence concerning which character combinations actually occurred in extinct organisms; in a phylogenetic context, fossil taxa have the potential to break up accumulations of synapomorphies below nodes, thus indicating which characters may have occurred in combination in heretofore unobserved extinct organisms. This attribute of fossil taxa is especially relevant in the context of joint extinct-extant taxon analyses, where the extant terminal taxa may be widely separated from one another due to the extinction of intermediate (“mosaic”) morphologies. When character mapping is combined with minimum age mapping on a phylogenetic tree, inferences can also be made about the minimum time of appearance of synapomorphies. While possibly intrinsically interesting, such an approach can aid, for instance, in inferring the minimum time of appearance of a group defined by a particular synapomorphy and has potential for testing evolutionary hypotheses of cause-effect relationships where both the putative cause and the putative effect can be temporally constrained.
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1 - University of Kansas, Ecology and Evolutionary Biology, Haworth Hall, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045-7534, USA
2 - University of Kansas, Department of Geology, Lindley Hall, Lawrence, Kansas, 66045-7534, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 2:30 PM