Submitted to: Systematic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2007
Publication Date: 6/1/2007
Citation: Sword, G.A., Senior, L., Gaskin, J.F., Joern, A. 2007. Double trouble for grasshopper molecular systematics: intra-individual heterogeneity of both mitochondrial 12S-valine-16S and nuclear internal transcribed spacer ribosomal DNA sequences in Hesperotettix viridis (Orthoptera: Acrididae). Systematic Entomology. 32(3):420-428.
Interpretive Summary: We often analyze DNA to determine relationships of species. We found that there is variation in DNA within an individual grasshopper, which can confound studies of relationships of species. This is the first finding of its kind in the grasshopper subfamily Melanoplinae. We suggest that future research determine if there are multiple varying copies of DNA within individual grasshoppers before continuing with studies of relationship of species.
Technical Abstract: Hesperotettix viridis grasshoppers (Orthoptera: Acrididae:Melanoplinae) exhibit intra-individual variation in both mitochondrial 12S-valine-16S and nuclear internal transcribed spacer (ITS) ribosomal DNA sequences. These findings violate core assumptions underlying DNA sequence data obtained via polymerase chain reaction (PCR) amplification for use in molecular systematics investigations. Undetected intra-individual variation of this sort can confound phylogenetic analyses at a range of taxonomic levels. The use of a DNA extraction protocol designed to enrich mitochondrial DNA as well as an initial long PCR of approximately 40% of the grasshopper mitochondrial genome failed to control for the presence of paralogous mitochondrial DNA-like sequences within individuals. These findings constitute the first demonstration of intra-individual heterogeneity in mitochondrial DNA-like sequences in the grasshopper subfamily, Melanoplinae, and only the second report of intra-individual variation in nuclear ITS ribosomal DNA sequences in grasshoppers. The fact that intra-individual variation was detected in two independent DNA marker sets in the same organism strengthens the notion that the orthology of PCR-derived DNA sequences should be examined thoroughly prior to their use in molecular phylogenetic analyses or as DNA barcodes.