XVI International Botanical Congess

The gene for NADH dehygrogenase subunit 1 includes four introns, one of which (the b-c intron) is examined here. It is a Type II intron with characteristic secondary structure and highly conserved, but with sufficient variation to be phylogenetically useful in Orchidaceae. Variation includes both base substitutions and length changes and is largely confined to large loop structures in the molecule. Both short directly repeated sequences and much larger insertions are present, as are deletions of varying size. More major changes are also present, including one deletion that characterizes Orchidoideae and alters the form of the molecule. Phylogenetic analysis of this variation reveals groups similar to those recovered with chloroplast and nuclear loci.