Calibrating the ages of conifer clades.

ESCAPA, IGNACIO; ROTHWELL, GAR; CÚNEO, RUBÉN

New Orleans

Congreso; Botany 2013; 2013

In recent decades there has been a progressively growing appreciation for the benefits of extensive taxon samplings on the accuracy of phylogenetic estimates. Both empirical studies and simulation analyses have found that extensive taxon sampling can affect the relationships inferred for a given group; and that fossils are often among the most influential taxa. Despite this, the number of molecular studies including exclusively extant taxa has increased dramatically, and therefore modern systematics face two crucial challenges: 1) whether the topology of systematic trees developed from only living species accurately reflect the overall pattern of phylogeny for the clade, and 2) the calibration of those phylogenetic hypothesis to geologic time. In this presentation we address the second of these challenges. When considering the use of a fossil as calibration point it is necessary to take into account several important parameters, such as method of identification and placement of an extinct species, the quality of preservation of the specimens, and the method, quality and uncertainty in the age determination for the fossils. In this context, paleontologists are indeed the best possible source for this information, providing more reliable calibration points for those molecular biologists wishing to clean up their molecular clocks. Clade age calibration points for conifers have increased in number and in confidence of accuracy as a result of outcomes obtained in the recent Gymnosperms AToL collaboration. Therefore, we are able to provide a number of fossil calibrations for conifers, including the nodes of the crown group for Araucariaceae, Podocarpaceae, Pinaceae, Cupressaceae and the less diverse families, together with other fossils that calibrate important nodes within each family.