The Song Laboratory of Insect Systematics and Evolution

Nuclear mitochondrial pseudogenes (numts) are non-functional copies of mtDNA in the nuclear genome which have been found in the major clades of eukaryotic organisms. Among insects, Orthoptera, especially grasshoppers, are known to have exceptionally high numbers of numts although the exact mechanism for nuclear integration is not well understood.

The presence of numts poses a challenge for PCR-based mitochondrial systematics because inadvertent coamplification or preferential amplification of numts can occur, thereby compromising the orthology assumption of characters. This line of research stemmed from my own struggle with generating mitochondrial sequences from grasshoppers, which has serendipitously transformed into an exciting area of research.

My research demonstrated that standard barcoding primers can easily coamplify numts of COI gene from diverse lineages within arthropods (insects and crustaceans), that some numts are difficult to identify because they do not have characteristic stop codons or indels, and that numt coamplification can potentially overestimate the number of species in DNA barcoding.

Currently, as a part of the NSF project, I am documenting a similar phenomenon in other genes within mtDNA from 25 major lineages of Orthoptera. I am also investigating a potential use of numts as phylogenetically informative characters because they represent ancient forms of mtDNA or molecular fossils, silently lodged in the nuclear genome.