Diagnostic and Phylogenetic Utility of the rDNA Internal Transcribed Spacer Sequences of Steinernema
Keywords:
entomopathogenic nematodes, evolution, its region, molecular systematics, nematode, phylogeny, ribosomal dna, species delimitation, species diagnosis, systematics, taxonomyAbstract
The ITS regions of 10 species of Steinernema were PCR amplified and directly sequenced. Restriction mapping of these sequences revealed diagnostic variation such that the number of cuts and the length of the resulting fragments can be used to diagnose Steinernema species. Nevertheless, identical fragment sizes produced by non-homologous restriction sites also were identified. Pronounced variation in sequence length and nucleotide composition resulted in optimized alignments containing extensive regions of dubious homology. Significant shifts in nucleotide base composition exist among taxa and appear to mirror evolutionary history. These shifts do not have an observable influence on phylogenetic reconstruction and are probably due to descent as opposed to convergence. Alignment instability and the presence of alignment-ambiguous regions had the greatest effect on phylogeny reconstruction. Our results support the taxonomic utility of the ITS region to diagnose nematode species of the genus Steinernema, and all sampled taxa show evidence (in the form of numerous autapomorphic characters) of lineage independence. However, the ITS region appears to be phylogenetically informative only for closely related sister species. High variability among more distantly related taxa preclude its use for confidently resolving relationships among all members of the genus.Downloads
Published
Issue
Section
License
Copyright and Permissions
All material published by the Society of Nematologists (SON), except for papers prepared by United States and Canadian government employees, is copyrighted and protected under the U.S. copyright law. Under the Copyright Act of 1976, the term of copyright for materials registered by an organization is 75 years from the date first published. Before publishing any manuscript, SON requires that authors transfer full and complete ownership of any copyright to SON by signing a JON Page Charge/Copyright Form (.pdf). SON then registers the copyright. Subsequent use of published materials requires written permission from the SON and may be obtained by contacting the current Editor-in-Chief and state where and how the material will be used.
The author warrants that the article is an original work not published elsewhere in whole or in part, except in abstract form, and that the author has full power to make this grant. If portions of the article have been published previously, then the author warrants that permission has been obtained from the copyright holder and the author will submit a copy of the permission release with this copyright transfer form.
SON shall claim no proprietary right other than copyright. Authors and coauthors retain the right to revise, adapt, modify, or otherwise use all or part of the article in future works of the author(s), such as press releases, lectures, and reviews, provided that all such use is for the personal noncommercial benefit of the author(s). All patent rights are retained by the author(s).
