J Syst Evol ›› 2010, Vol. 48 ›› Issue (4): 271-278.

• Research Articles •

### Adding time-calibrated branch lengths to the Asteraceae supertree

Rubén TORICES*

1. (Área de Botánica, Departamento de Ciencias Agroforestales, Universidad de Valladolid, E-42004, Soria, Spain)
• Received:2010-03-12 Published:2010-07-20

Abstract: New inference techniques, as supertrees, have improved the construction of large phylogenies helping to reveal the tree of life. In addition, these large phylogenies have enhanced the study of other evolutionary questions as whether traits have evolved in a neutral or adaptive way, or what factors have influenced diversification. However, supertrees usually lack branch lengths, which are necessary to study all these issues. Here, divergence times within the largest family of flowering plants, Asteraceae, are reviewed for estimating time-calibrated branch lengths in the supertree of this lineage. An inconsistency between estimated dates of basal branching events and the earliest asteraceous fossil pollen record was detected. In addition, I explored how different methods of branch lengths assignment may influence the total number of transitions between states in the reconstruction of sexual system evolution in Asteraceae. At least for this data set, different branch length assignation approaches only influenced maximum likelihood reconstructions but not Bayesian ones. The selection of different branch lengths information, therefore, is not arbitrary and it should be carefully assessed at least when ML approaches are being used. The reviewed divergence times and the estimated time-calibrated branch lengths provide a useful tool for future phylogenetic comparative and macroevolutionary studies of Asteraceae.