COMPARISONS OF 2 POLYMORPHIC SPECIES OF OSTERTAGIA AND PHYLOGENETIC-RELATIONSHIPS WITHIN THE OSTERTAGIINAE (NEMATODA, TRICHOSTRONGYLOIDEA) INFERRED FROM RIBOSOMAL DNA REPEAT AND MITOCHONDRIAL-DNA SEQUENCES

The first internal transcribed spacer DNA (ITS-1) (rDNA) and the mitoc hondrial (mt) DNA-derived cytochrorne oxidase I gene (COX-1) were enzy matically amplified, cloned and sequenced from 6 nominal species of Os tertagiinae as well as Haemonchus contortus and Haemonchus placei. The portion of the COX-1 gene analyzed was 393 base pairs (bp) in length and contained 33 within species polymorphic base changes at 28 synonym ous sites. The ITS-1 rDNA consensus sequences ranged from 392 bp (Oste rtagia ostertngi/Ostertagia lyrata, Teladorsagia circumcincta) to 404 bp (H. contortus, H. placei). These data were used both in a distance analysis to assess the concept of polymorphic species within the genus Ostertagia and in parsimony analysis to assess phylogenetic relations hips within a limited group of Ostertagiinae. Pairwise similarity scor es of both ITS-1 and COX-1 data showed the highest number of conserved sites between the proposed dimorphic species of Ostertagia. The level of similarity was lower in the COX-I data due to the high number of s ynonymous base changes. Analysis by maximum parsimony of the same data did not refute O. ostertagi/O. lyrata and Ostertagia mossi/Ostertagia dikmansi as dimorphic species and supported monophyly of these ostert agiines relative to representatives of the haemonchine outgroup. In th e single most parsimonious tree from ITS-1 rDNA data, a subclade of Os tertagia spp. included forms possessing parallel synlophes and long es ophageal valves that typically occur in cervid hosts.