Data decisiveness, data quality, and incongruence in phylogenetic analysis: an example from the monocotyledons using mitochondrial atp A sequences

We examined three parallel data sets with respect to qualities relevant to phylogenetic analysis of 20 exemplar monocotyledons and related dicotyledons. The three data sets represent restriction site variation in the inverted repeat region of the chloroplast genome, and nucleotide sequence variation in the chloroplast-encoded gene rbcL and in the mitochondrion-encoded gene atpA, the latter of which encodes the *-subunit of mitochondrial ATP synthase. The plant mitochondrial genome has been little-used in plant systematics, in part because nucleotide sequence evolution in enzyme-encoding genes of this genome evolve relatively slowly. The three data sets were examined in separate and combined analyses, with a focus on patterns of congruence, homoplasy, and data decisiveness. Data decisiveness (described by P. Goloboff) is a measure of robustness of support for most-parsimonious trees by a data set in terms of the degree to which those trees are shorter than the average length of all poss...