Land Plant Evolution: Phylogenetics and Beyond
Berbee, Mary L. , Taylor, John W. .
Fungi and early land plants; predictions from molecular phylogenetics and the fossil record.
PHYLOGENETIC inference and fossil evidence show that fungi in four phyla had originated by the Devonian, 400 million years ago. Many early fungal fossils were associated with early plants. Of the fungal phyla, most extant members of the Ascomycota, Basidiomycota and Glomales depend on living or dead plant material as a source of nutrients. In theory, assuming a molecular clock could allow for comparisons of divergence times of early land plants and early terrestrial fungi. Phylogenies for both fungi and plants are increasingly reliable, which should be increasing the accuracy of estimates of divergence times. However, the fungal fossil calibration points are few and difficult to interpret, and this combined with apparently chaotic evolutionary rate variation has resulted in an astonishing range of estimates for ages (e.g., for the first divergence in the Fungi, from 570 Ma Berbee and Taylor 1993 to 1,460 Ma in Heckman et al., 2001). The oldest age estimates place origins of terrestrial fungi 500 million years before the first estimate for terrestrial plants. We explored the consequences of alternative calibration points in a phylogeny based on 50 nuclear gene sequence regions, and show that rate variation across lineages, combined with choice of calibration points, has a dramatic effect on divergence age estimates. We speculate about the kinds of data that will improve estimates of fungal divergence dates in the near future.
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1 - University of British Columbia, Botany Department, 3529-6270 University Boulevard, Vancouver, British Columbia, V6T 1Z4, Canada
2 - University of California, Berkeley, Plant and Microbial Biology, 111 Koshland Hall MC 3102, Berkeley, California, 94720-3102, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Monday, July 31st, 2006
Time: 3:35 PM