Preliminary work is needed to assess the usefulness of different markers at different taxonomic scales when a new group is analyzed, such as the commercially important Phytoseiidae mites. We investigate here the level of sequence variation of the nuclear ribosomal spacers ITS 1 and 2 and the 5.8S gene in six species of Phytoseiidae: Neoseiulus culifornicus, N. fallacis, Euseius concordis, Metaseiulus occidentalis, Typhlodromus pyri and Phytoseiulus persimilis. As expected, the 5.8S gene (148 base pairs) is markedly conserved and displays little variation in between genera comparisons. ITS1 and ITS2 show contrasting patterns: while the ITS2 is short (80-89 bp) and shows little variation, the ITS1 is longer (303-404 bp) and is very variable in sequence. This fact compromises reliable nucleotide homologies when comparing the genera. The comparison of ITS1 sequence similarity at the species level might be useful for species identification, however, the value of ITS in taxonomic studies does not extend to the level of the family. The intraspecific variations of ITS were investigated in three species: N. californicus, N. fallacis and E. concordis. The first species has identical ITS1 sequences and the last two display low polymorphism (2 nucleotide substitutions). The ITS2 and 5.8S sequences were identical in all three subspecies comparisons.
Raworth, D.A., Fauvel, G. and Auger, P., 1994. Location, reproduction and movement of Neoseiulus californicus (Acari: Phytoseiidae) during the autumn, winter and spring in orchards in the south of France. Exp. Appl. Aearol,, 18; 593~502.
Sequence variation of the complete second internal transcribed spacer (ITS2, 445 bp) of nuclear ribosomal DNA and part of the mitochondrial cytochrome oxidase I gene (COI, 350 bp) was examined in Amphitetranychus viennensis (Zacher) mites (Acari:Tetranychidae) from four French and four Japanese locations. Sequence analysis consistently revealed the separation of the samples in two major groups: French mites differed from Japanese by 3.8–4.1% of the nucleotide divergence in COI sequences. These two groups also displayed distinct ITS2 consensus sequences (2.1% nucleotide divergence). A few variations, not affecting the diagnostic sites around the consensus sequence, were revealed among cloned copies of the same individual. Reciprocal crosses and backcrosses between one French and two Japanese populations disclosed strong reproductive incompatibility. However, fertile hybrid females were obtained, indicating the conspecificity of the tested mites. Despite the presence of Wolbachia in the French strain, but not in the Japanese ones, our crosses did not display the unidirectional incompatibility typically produced by this microorganism, but rather a bidirectional – although asymmetrical – incompatibility pattern. The post‐zygotic incompatibilities in A. viennensis cannot be explained by the presence of Wolbachia but to some extent by mite genome divergence resulting from limited gene exchange between allopatric populations. Experiments of Wolbachia elimination by antibiotic treatment and subsequent crosses with cured strains are still needed to fully understand the reproductive incompatibility patterns in this mite species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.