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The heritable endosymbiotic bacterium Spiroplasma is found in the harlequin ladybird Harmonia axyridis. The proportion of beetles infected with Spiroplasma in different native H. axyridis populations varies from 2% to 49%. We investigated the polymorphism of Spiroplasma strains in samples from individual beetles from Kyoto, Vladivostok, Troitsa Bay, Novosibirsk, and Gorno-Altaisk. To identify Spiroplasma strains, we analyzed nucleotide polymorphisms of the 16S rRNA gene and the ribosomal internal transcribed spacer (ITS1). The majority of infected beetles were infected with two or more Spiroplasma strains. We measured Spiroplasma density in beetles with different infection status using quantitative PCR. The abundance of Spiroplasma in samples with a single infection is an order of magnitude lower than in samples with multiple infections. Density dependent biological effects of Spiroplasma are discussed.

We present comparative analysis of mitogenomics data of the Drosophila virilis group based on newly obtained complete mt-genome sequence of Drosophila littoralis, previously published mt-genome sequence of D. virilis and fragments of mt-genomes of other Drosophila species belonging to the virilis group. Drosophila of the virilis group shared most recent common ancestry 40 MYA with D. melanogaster. Therefore, presented data help to overview the evolution of the genus. The mt-genome of D. littoralis is a circular molecule of 16,017 bp with a total A+T content of 76.2%. The gene order is consistent with other Drosophila genomes. All tRNAs can be folded in the form of a typical clover-leaf structure except for tRNASer(AGN). In the control region of D. littoralis we found four conserved sequence elements: 275 bp highly conserved sequence element, two thymidylate stretches and a G-island. The most variable genes in Drosophila of the virilis group are nad6, nad3 and nad4L. The most conservative is cox1. We revealed long intergenic sequences’ (TA)n separating atp6 and cox3 genes in the mitochondrial genomes of Drosophila of the virilis group. In other insect species these genes have no or few separating nucleotides. We detected fragments of mitochondrial genes atp6 and cox3 in the nuclear genome of D. virilis. These mitochondrial pseudogenes are marked by site-specific insertions of Tv1 retrotransposon in the (TA)n intergenic spacer sequences

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