Wolbachia symbionts are maternally inherited bacteria that are widely distributed among Arthropoda hosts. Wolbachia influence their host biology in diverse ways. They may induce reproductive abnormalities, protect hosts against pathogens and parasites, or benefit hosts through metabolic provisioning. The progeny of an infected female are ordinarily infected with Wolbachia; however, Wolbachia have no future in male host progeny because they cannot transmit the symbiont to the next generation. Here, we analyze native and invasive populations of the four-eyed fir bark beetle (Polygraphus proximus) for Wolbachia prevalence and symbiont genetic diversity. This species is a dangerous pest of Siberian fir (Abies sibirica) forests. The native range of P. proximus includes the territories of the Russian Far East, Japan, Korea, and Northeast China, whereas its invasive range includes West Siberia, with further expansion westward. Surprisingly, we revealed a difference in the patterns of Wolbachia prevalence for males and females. Infection rate and Wolbachia titers were higher in females than in males. ST-533, the only haplotype of Wolbachia supergroup B, was associated with a minimum of three out of the five described mitochondrial haplotypes.

No abstract

Insects play an important role in biocenoses due to their abundance and wide (cosmopolitan) distribution. Many insects are crop pests. An effective pest control could be realized in case of proper species identification, which is usually managed by morphological analysis. Molecular methods allow to deep study of many issues of insect biology. In particular, traditional approach can not ordinary identify a species at all stages of their life cycle, whereas molecular methods can it. This review covers a wide range of issues related to the molecular genetic analysis of insects. In the first section we consider the methods of fixation and storage of insect specimens, as well as their impact on DNA quality. Further, we provide general information on population study design. Various schemes of DNA extraction, examples of both express techniques and more thorough protocols for DNA extraction and their purification are provided. In addition, methods of DNA isolation that allow to preserve a specimen integrity for further morphological studies are considered. The methods of DNA quality control are described in detail, that is important for PCR analysis. The last section provides various methods of PCR analysis, that we exemplify by studies aimed to elucidate both fundamental issues and practical problems.

Symbiotic bacteria of the genus Wolbachia are widespread in Drosophila melanogaster populations. Based on the polymorphism of the Wolbachia genome, the symbionts’ diversity in D. melanogaster is presented by two groups: MEL (wMel, wMel2, wMel3 and wMel4) and CS (wMelCS and wMelCS2). The wMel genotype is predominant in natural D. melanogaster populations and is distributed all over the world. The CS genotypes, on the other hand, are of particular interest because it is unclear how they are maintained in the fruit f ly populations since they should have been eliminated from them due to their low frequency and genetic drift or been replaced by the wMel genotype. However, this is not what is really observed, which means these genotypes are supported by selection. It is known that the wMelPlus strain of the wMelCS genotype can increase the lifespan of infected f lies at high temperatures. The same genotype also increases the intensity of dopamine metabolism in Drosophila compared to the MEL-group genotypes. In the present study, we searched for the rare Wolbachia wMelCS and wMelCS2 genotypes, as well as for new genotypes in wild-type D. melanogaster strains and in several mutant laboratory strains. The symbiont was found in all populations, in 200 out of 385 wild-type strains and in 83 out of 170 mutant strains. Wolbachia diversity in D. melanogaster wild-type strains was represented by the wMel, wMelCS and wMelCS2 genotypes. More than 90 % of the infected strains carried wMel; 9 %, wMelCS2; and only two strains were found to carry wMelCS. No new Wolbachia genotypes were found. The northernmost point reported for the wMelCS2 genotype was Izhevsk city (Udmurtia, Russia). For the f irst time the wMelCS2 genotype was detected in D. melanogaster from the Sakhalin Island, and wMelCS, in the f lies from Nalchik (the North Caucasus). A comparison of Wolbachia genetic diversity between the wild-type laboratory strains and previously obtained data on mutant laboratory strains demonstrated differences in the frequencies of rare CS genotypes, which were more prevalent in mutant strains, apparently due to the breeding history of these Drosophila strains.