Dj. Funk et al., MITOCHONDRIAL-DNA SEQUENCES AND MULTIPLE DATA SETS - A PHYLOGENETIC STUDY OF PHYTOPHAGOUS BEETLES (CHRYSOMELIDAE, OPHRAELLA), Molecular biology and evolution, 12(4), 1995, pp. 627-640
This paper presents the phylogenetic infrastructure for an integrated
historical and experimental study of host use evolution in the chrysom
elid leaf beetle genus Ophraella. We report the collection of sequence
data from the 16S ribosomal RNA (446 bp) and the cytochrome oxidase s
ubunit I (420 bp) mitochondrial genes from 12 species of Ophraella and
two outgroups. Sequence analysis revealed a strong A+T nucleotide bia
s, high interspecific COI sequence divergences (up to 21.4%) that grea
tly exceeded those for 16S (up to 5.9%), high intraspecific COI diverg
ences (up to 3.8%), a dearth of amino acid substitutions in COI, and d
iffering substitution patterns in ribosomal stems and loops. Intraspec
ific variation in COI haplotypes generally supported the genealogical
coherence of Ophraella lineages, while suggesting two cases of paraphy
letic species. Separate phylogenetic analyses of 16S and COI data sets
yielded largely congruent trees. A combined 16S + COI analysis yielde
d a single shortest tree under maximum parsimony that was identical to
trees provided by successive approximations, neighbor-joining, and ma
ximum-likelihood methods. This topology proved robust to various forms
of weighting and most nodes were highly supported (by bootstrap analy
sis). Separate parsimony analyses of mtDNA and previously collected mo
rphological and electromorphic data sets revealed congruent estimates
of all cladistic relationships except those within one clade. Analysis
of the pooled data sets in a combined approach additionally provided
support for the basal placement of two species from this clade, althou
gh the topology for the remaining species was weakly supported and inc
ongruent with the mtDNA tree. Each data set contained significantly st
ructured phylogenetic signal with respect to this clade, and data sets
exhibited limited conflict (character incongruence) with each other.
The combined data set, however, was found to lack phylogenetic signal.
These observations may imply that pooling heterogeneously evolving cl
asses of data obscured the phylogenetic signal in each, a potential li
mitation of the combined approach.