Deep Time: Integrating Paleobotany and Phylogenetics
Magallón, Susana .
Alternative methods for integrating living and extinct taxa with missing data in phylogenies: biological implications for Hamamelidaceae (Saxifragales, core eudicots).
Continued advances in our understanding of phylogenetic relationships, together with the recent availability of highly informative fossils, provide an unprecedented opportunity for an accurate reconstruction of angiosperm evolutionary history. This potential may only be realized by integrating living and extinct taxa in a phylogenetic framework which will provide explicit information about timing and rate of phylogenetic branching, morphological evolution and biogeographic history. Phylogenetic integration of living and extinct taxa may nevertheless be complicated by differential availability of morphological and molecular characters. Here, I evaluate the effect of increasing missing data in total evidence analysis, and the relative effectiveness of morphological parsimony analysis constrained with a molecular backbone, using living and extinct members of Hamamelidaceae (Saxifragales), and a data set consisting of 55 floral characters and ca. 4800 base pairs of four chloroplast molecular markers. Independent analyses of morphological and molecular data result in different topologies, but strongly supported incongruence does not exist. A series of total evidence (TE) parsimony analyses evaluated the effect of increasing missing data. The first TE analysis included only complete taxa, and resulted in a well resolved tree in which many nodes were strongly supported. Adding two living taxa lacking molecular data produced a local collapse in the clade that contains the added taxa. Further inclusion of three fossils resulted in a substantial decrease in phylogenetic resolution among Hamamelidaceae. A parsimony analysis of morphological data constrained with a backbone derived from well supported relationships obtained from molecular data resulted in a well resolved tree that unequivocally indicates relationships among extinct and living taxa. The nested position of the fossils among living taxa indicates that a substantial amount of phylogenetic diversification and floral evolution within Hamamelidaceae had taken place by the Santonian/Campanian, and document former geographical distributions that expand present-day ranges.
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1 - Universidad Nacional Autónoma de México, Department of Botany, 3er Circuito de Ciudad Universitaria, Del. Coyoacán, Mexico City, México D.F., 04510, Mexico
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 4/Hilton
Date: Monday, July 9th, 2007
Time: 2:00 PM