Parasitology, Harold W. Manter Laboratory of

 

Date of this Version

2000

Citation

Journal of Parasitology (2000) 86(3): 588-601.

Comments

U.S. government publication.

Abstract

Nuclear ribosomal sequence data from the internal transcribed spacers (ITS-1 and ITS-2), 5.8S subunit, and regions of the 18S and 28S genes were used to investigate sequence diversity among geographic samples of Nematodirus battus, and to infer phylogenetic relationships among Nematodirus species. Phylogenetic analysis of these data yielded strong support for relationships among species, depicting Nematodirus helvetianus and Nematodirus spathiger as sister-taxa and a clade of these two species and Nematodirus filicollis. This tree is consistent with caprine bovids as ancestral hosts, with a subsequent host shift to Bovinae in N. helvetianus. Eleven of fourteen N. battus sequences were unique, with nineteen variable sites among sequences representing five geographic samples. The lowest number of variable nucleotide sites was observed in samples representing apparently recent introductions to the United States and Canada, which is consistent with a population bottleneck concomitant with translocation. Comparison of directly sequenced polymerase chain reaction products and clones revealed evidence for intraindividual variation at some of the sequence sites, and this pattern of varaiation and that within geographic samples indicates incomplete rDNA repeat homogenization within species. This pattern of variation is not conducive for inferring phylogenetic relationships among sequences representing N. battus or addressing the putative history of introduction.

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