Heterogeneity of the internal transcribed spacer (ITS-2) region within individual deer ticks.

TitleHeterogeneity of the internal transcribed spacer (ITS-2) region within individual deer ticks.
Publication TypeJournal Article
Year of Publication1997
AuthorsRich SM, Rosenthal BM, Telford SR, Spielman A, Hartl DL, Ayala FJ
JournalInsect Mol Biol
Date Published1997 May
KeywordsAnimals, Base Sequence, Deer, DNA, DNA, Ribosomal, Genetic Heterogeneity, Ixodes, Molecular Sequence Data

To determine whether nuclear rDNA sequences provide a useful means for assessing the structure of populations of Ixodes ticks, we compared variability among copies of an internal transcribed spacer (ITS-2) sequence within individual ticks to the variability between ticks. At least 4% of the nucleotides comprising this sequence vary among the copies present within individual ticks. ITS-2 diversity in each of two ticks is nearly half as great as that reported between ticks from geographically disparate populations. Because individual ticks retain ancestral polymorphism, ITS-2 variation does not accurately reflect descent relationships among these ticks. Sequencing single copies of PCR-amplified ITS-2 therefore does not permit assessment of the phylogenetic relationships among the I. ricinus-like ticks in eastern North America. We recommend caution in future analyses, and emphasize the importance of procedures designed to ensure that the many paralogous copies of the rDNA cistron have been sufficiently homogenized by concerted evolutionary processes. Such precautionary measures will make certain that phylogenetic trees based on these gene sequences reflect the phyletic relatedness of the biological species.

Alternate JournalInsect Mol. Biol.
PubMed ID9099576