Dp. Mindell et al., MULTIPLE INDEPENDENT ORIGINS OF MITOCHONDRIAL GENE ORDER IN BIRDS, Proceedings of the National Academy of Sciences of the United Statesof America, 95(18), 1998, pp. 10693-10697
Mitochondrial genomes of all vertebrate animals analyzed to date have
the same 37 genes, whose arrangement in the circular DNA molecule vari
es only in the relative position of a few genes. This relative conserv
ation suggests that mitochondrial gene order characters have potential
utility as phylogenetic markers for higher-level vertebrate taxa. We
report discovery of a mitochondrial gene order that has had multiple i
ndependent originations within birds, based on sampling of 137 species
representing 13 traditionally recognized orders. This provides eviden
ce of parallel evolution in mitochondrial gene order for animals. Our
results indicate operation of physical constraints on mitochondrial ge
ne order changes and support models for gene order change based on rep
lication error. Bird mitochondria have a displaced Or (origin of light
-strand replication site) as do various other Reptilia taxa prone to g
ene order changes. Our findings point to the need for broad taxonomic
sampling in using mitochondrial gene order for phylogenetic analyses.
We found, however, that the alternative mitochondrial gene orders dist
inguish the two primary groups of songbirds (order Passeriformes), osc
ines and suboscines, in agreement with other molecular as well as morp
hological data sets. Thus, although mitochondrial gene order character
s appear susceptible to some parallel evolution because of mechanistic
constraints, they do hold promise for phylogenetic studies.