Ke. Omland, CHARACTER CONGRUENCE BETWEEN A MOLECULAR AND A MORPHOLOGICAL PHYLOGENY FOR DABBLING DUCKS (ANAS), Systematic biology, 43(3), 1994, pp. 369-386
This paper presents an analysis of data from two published phylogenies
of North American dabbling ducks (Anns), one based on mitochondrial D
NA restriction fragments (Kessler and Avise, 1984, Syst. Zool. 33:370-
380) and one based on morphology (Livezey, 1991, Auk 108: 471-508). Al
though the published phylogenies differ greatly in topology, most of t
he apparent disagreement stems from the phenetic rooting method used i
n the molecular study. Rooting by outgroup and using the same taxa fro
m both data sets revealed that the most-parsimonious trees for the two
data sets differ only in the placement of one clade. Furthermore, sev
eral lines of evidence show that there is greater character congruence
between the molecular and morphological data sets for these ducks tha
n for most other taxa for which data are published: (1) an incongruenc
e index (I-MF; Mickevich and Farris, 1981, Syst. Zool. 30:351-370) dem
onstrates that only 1.35% of the character incongruence in the combine
d data is due to incongruence between the data sets; (2) for each data
set, trees only a few steps longer than the shortest tree match the m
ost-parsimonious tree from the other data set; and (3) a way of applyi
ng correlation coefficients to branch lengths reveals a high correlati
on in branch lengths (r(BL) = 0.78) and total evolutionary changes (r(
TE) = 0.68) between matching phylograms from the two data sets. These
correlations also show that the two character types evolved at similar
relative rates in any given lineage, even though there were real rate
differences between lineages. The high degree of character congruence
means that the discrepancy between the most-parsimonious trees are du
e to insufficient data, not real disagreement. This situation warrants
combining the data sets, and the resulting shortest cladogram is more
strongly supported than is either of the shortest trees from the indi
vidual data sets. The correspondence between the data sets validates t
he soundness of the inferred trees, showing that they are a reliable b
asis for classification and studies of character evolution.