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Abstract Detail


Paleobotanical Section

Seyfullah, Leyla J. [1], Hilton, Jason [1], Bateman, Richard M. [2].

Root of despair? Experimenting on outgroup selection in lignophyte phylogeny.

Experimental morphological cladistic analyses of lignophytes (progymnosperms plus seed-plants) highlight the profound effects that outgroup selection plays on topology generated and especially on perceptions of character polarity and evolution. Alternative outgroup choices among progymnosperms produce wildly divergent topologies. Using either the aneurophyte Tetraxylopteris or the archaeopterid Archaeopteris produces topologies and character polarities that are broadly consistent with analyses within seed-plants rooted on the early seed-plant Elkinsia, but that have subtle changes in the position of various extinct and extant groups. By contrast, rooting on the putative progymnosperm Cecropsis places a Bennettitales + Caytonia + Angiosperms clade basal-most in the tree, and in general inverts polarity in comparison with analyses rooted on Elkinsia. This talk will summarize recent findings from cladistic experimentation on outgroup selection, addressing the use of trimerophytes and other Devonian tracheophyte groups for rooting lignophytes in order to test competing theories of seed-plant origins from among progymnosperms. Results have wide-ranging implications for both morphological and molecular phylogenetic treatments of seed plants, and highlight the significance of various important character polarity inversions noted in previous studies.


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1 - University of Birmingham, Earth Sciences, School of Geography, Earth and Environmental Science, Edgbaston, Birmingham, B15 2TT, U.K.
2 - Jodrell Laboratory, Royal Botanic Gradens, Kew, Richmond, Surrey, TW9 3DS, U.K.

Keywords:
Seed plant
outgroup selection
character polarity.

Presentation Type: Oral Paper:Papers for Sections
Session: 7
Location: 169/Law
Date: Monday, July 28th, 2008
Time: 8:45 AM
Number: 7002
Abstract ID:519


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