Figure 4

Fig. 4. The limit for resolution of cladogenetic events of Cambrian age, under the best of circumstances, may be an order of magnitude higher than previously thought. The phylogenetic accuracy with which internodes are resolved (the ordinate) is plotted against the length of each internode in million years (the abscissa). Data sets of two different lengths (data set in blue, 16,000 characters, of which 6000 are variable; data set in red, 73,000 characters, of which 28,000 are variable) were generated by simulation, assuming a tree with a 600-million-year time span. For many internodes with lengths much higher than 1 million years, resolution accuracy values are low, irrespective of data set size. Not all internodes of a given age exhibit the same resolution accuracy. For example, certain 3-million-year internodes are resolved with 100% accuracy, whereas other internodes of similar (or greater) age exhibit much lower values of resolution accuracy. Results are shown for analyses using MP [similar results are obtained by NJ analyses (fig. S7)]. [View Larger Version of this Image (69K JPEG file)]

 

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