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Abstract

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.

Diversity of Phylogenetic Information According to the Locus and the Taxonomic Level: An Example from a Parasitic Mesostigmatid Mite Genus

“…Observed divergence percentages are presented in Table 3. These elementary datasets may be split into three groups according to their characterization power: COI, 16S and Tropomyosin intron n are very informative at the specific and intraspecific levels, as usually noted in other arthropods.ITS1 and 2 are moderately informative at the specific level and weakly variable within species, contrary to observations of close relatives (Dermanyssoidea: Rhinonyssidae [27,28]), although more similar to other mesostigmatids (Ascoidea: Phytodeiidae [29]).5.8S and Tropomyosin exon n and n + 1 are insufficiently informative at the specific level and do not show any intraspecific variation, as expected.…”

Carboxylesterase gene amplifications associated with insecticide resistance in Aedes albopictus: Geographical distribution and evolutionary origin

“…albopictus adults or larvae stored in ethanol were first dried, and then genomic DNA was extracted from each individual using the Cethyl Trymethil Ammonium Bromide (CTAB) method described in Navajas et al [37]. The DNA pellet was dissolved in 20μl of sterile water.…”

The nuclear genome of the phytoseiid Metaseiulus occidentalis (Acari: Phytoseiidae) is among the smallest known in arthropods

“…The complete mitochondrial genome has been sequenced and found to be unusually large (25 kb) and containing several novel features (Jeyaprakash and Hoy 2007). However, little sequence information for the nuclear genome is currently available; so far only a complete inactive mariner transposable element (Jeyaprakash and Hoy 1995) and the ITS1, 5.8S, and ITS2 regions (Navajas et al 1999) have been sequenced. Sequencing the nuclear genome of this phytoseiid could lead to the discovery of novel genes that are involved in characteristics such as predatory behavior, pesticide resistance, diapause and others.…”