Species-wide homogeneity of nuclear ribosomal ITS2 sequences in the spider mite Tetranychus urticae contrasts with extensive mitochondrial COI polymorphism

Abstract

We compared patterns of intraspecific polymorphism of two markers with contrasted modes of evolution, nuclear ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA), in the phytophagous mite Tetranychus urticae Koch. The second internal transcribed spacer (ITS2) of rDNA and a fragment in the mtDNA gene coding for Cytochrome Oxidase I (COI), were PCR-amplified and sequenced in samples of various geographical origins distributed worldwide. The 15 COI haplotypes found fell into two major phylogenetic lineages differing by an average of 5% nucleotide divergence. Samples from the Mediterranean basin were represented in both lineages, and showed no phylogeographical structure. The other samples, from temperate regions of the northern hemisphere, were clustered in one of the lineages and displayed little variation, indicating a recent colonization of this region. In contrast, no variation at all was found at the ITS2 in this species. We sequenced both COI and ITS2 in four other species of the genus Tetranychus and found that, despite the absence of intraspecific polymorphism, ITS appears to evolve 2.5 times faster than COI. We argue that rDNA homogeneity over the species range of T. urticae results from the high colonization potential of this species, preventing long-term differentiation. Preliminary data on two other mite species (Amphitetranychus viennensis Zacher and Mononychellus progresivus Doreste) with stricter ecological requirements and more restricted colonization potential revealed substantial and concordant geographical differentiation for both ITS2 and COI.

Is ITS-2 rDNA suitable marker for genetic characterization of Sarcoptes mites from different wild animals in different geographic areas?

“…In addition, Zahler et al (1998) and Essig et al (1999) were not able to find clear differences within the worldwide distributed genera Psoroptes and Chorioptes, respectively. However, Navajas et al (1998) showed extensive polymorphism in sequences of mitochondrial cytochrome oxidase I in T. urticae. Some sorts of geographical or host specificity in Sarcoptes populations have been shown in studies in which microsatellites were used as markers (Walton et al, 2004;Soglia et al, 2007).…”

“…The number of variable sites was very different among populations: the population ItNWVv was the most variable (30 mutations), whereas the ItNWMf (4 mutations) and SpNEVv (5 mutations ITS-2 rDNA appears to be suitable genetic marker for distinguishing closely related species and examining phylogenetic relationships within genera but not suitable for genetic characterization within a species for mites (Navajas et al, 1994(Navajas et al, , 1998Navajas and Fenton, 2000;Zahler et al, 1998Zahler et al, , 1999Essig et al, 1999;Berrilli et al, 2002). For example, Navajas et al (1998 found very low variation in ITS-2 sequences within Tetranychus urticae. Similar patterns of variation were found by Navajas et al (1994) for Mononychellus progresivus and, as mentioned above, by Zahler et al (1999) and Berrilli et al (2002) for Sarcoptes.…”

Comparison of four methods of extracting DNA fromD. gallinae(Acari: Dermanyssidae)

“…According to extraction methods already published for various acari (Eriophyidae, Ixodidae, Laelapidae, Phytoseiidae, Tetranychidae, Trombidiidae), we chose and compared three conventional methods for extracting DNA from D. gallinae: a CTAB method, with a lysis step followed by a phenol chloroform precipitation [17,20], a Qiamp DNA extraction kit using separation with a column [8,11], and a Chelex resin [10,14,21,25,28,29]. Another attractive method, the FTA technology, was also tested, and compared to the others.…”

Phylogeography of the neotropical sand fly Lutzomyia longipalpis inferred from mitochondrial DNA sequences

“…Little is known about the molecular genetics of this group of sand flies (Esseghir et al, 1997;Ready et al, 1997Ready et al, , 1998Ishikawa et al, 1999). However, studies of the molecular phylogenetics of other arthropod groups suggest that sequence from region I of the mitochondrial cytochrome c oxidase I (COI) gene might be informative for clarifying Lutzomyia taxonomy at the species level (Navajas et al, 1994(Navajas et al, , 1996(Navajas et al, , 1998Roderick and Gillespie, 1998). Here, we present a phylogeographical interpretation of L. longipalpis based on molecular phylogenetic analysis using mtDNA and available theories on the historical physical geography of Central and South America (Haffer, 1969;Howe, 1974;Keigwin, 1978;Haffer, 1981;Rod, 1981;Sykes et al, 1982;Stehli and Webb, 1985;Hoorn, 1994;Hoorn et al, 1995).…”