Pk. Flook et Chf. Rowell, THE EFFECTIVENESS OF MITOCHONDRIAL RIBOSOMAL-RNA GENE-SEQUENCES FOR THE RECONSTRUCTION OF THE PHYLOGENY OF AN INSECT ORDER (ORTHOPTERA), Molecular phylogenetics and evolution, 8(2), 1997, pp. 177-192
We investigated the value of mitochondrial rRNA sequences for analyzin
g pre-Cainozoic divergence events in insects. Using small subunit and
large subunit rRNA sequences from 38 orthopteroid species, we examined
several aspects of sequence evolution including secondary structure,
substitution rate, and base composition. Substitution matrices calcula
ted from the two genes were very similar, though differences were dete
cted in rates of C-T transitions between paired and unpaired positions
in secondary structures. By contrast, extreme disparities between sub
stitution frequencies at different phylogenetic levels make character-
transition weighting essential in parsimony reconstruction. The analys
is of base composition indicated that branch attraction of at least tw
o important lineages was due to shared base composition biases and to
long branch attraction, The importance of taxonomic sampling and seque
nce length for the effectiveness of phylogenetic recovery using the rR
NA fragments was also assessed. Significantly, combining the two seque
nces seemed both justifiable and necessary for this taxonomic sample.
However, for reconstructing deep branches of phylogeny, it seems that
increasing either or both the number of taxa or nucleotide positions w
ill not necessarily solve all problems. Instead, the resolution of anc
ient branching events using mtDNA sequences probably depends upon the
development and application of better specified reconstruction methods
. (C) 1997 Academic Press.