estimates were reported by Magallón et al. (1999) and Magallón and Sanderson (2001). In
addition, Table 8.1 gives details on both the fossil-based and molecular estimates.
Molecular estimates are given for all three analyses using parsimony (ACCTRAN and
DELTRAN) and maximum likelihood for calculating branch lengths, and also lists the
bootstrap estimates of standard error. Bootstrap estimates of standard error, as well as the
chronograms presented (Figures 8.3–8.6) are based on the analysis using parsimony
(ACCTRAN optimization) for calculating branch lengths, and the chronograms have been
generalized to a level enabling us to present graphically the comparison between our
molecular estimates and the fossil-based estimates (Magallón et al. 1999; Magallón and
Sanderson 2001). Complete details of the results, documenting age estimates for all
included taxa, have been presented elsewhere (Wikström et al. 2001).
Figure 8.2 Schematic drawing adopted from Magallón and Sanderson (2001) explaining our use of
crown-groups, stem-groups, and their ages. The crown-group age corresponds to the first
phylogenetic split within the crown-group and only fossils demonstrated to be nested within the
crown-group can provide a minimum age estimate for this group. The stem-group age may be
considerably older and corresponds to the split between the crown-group in question and its extant
sister group. Any representative, though preferably a stem one, may provide a minimum age
estimate for the stem-group. Also note that a minimum age estimate for the sister clade may
represent the best available age estimate for the stem-group.
154 ANGIOSPERM DIVERGENCE
Results
Results are presented in the form of chronograms (Figures 8.3–8.6), calibrated against the
geological timescale (Harland et al. 1990), focusing on taxa for which fossil-based