Recombination and dynamics of transposable elements in natural populations. A drosophilist’s view

The concept of the tight link between crossing over and the dynamics of transposable elements is presented. The behavior of transposable elements influences the processes of homologous recombination, both at the moment of activation and as a result the changes in a genome caused by active transposition of the autonomous nucleotide sequences

Low prevalence of Wolbachia infection in Ukrainian populations of Drosophila

Aim. The aim of this study was to determine the Wolbachia infection prevalence among Drosophila species that are common in Ukraine. Methods. The total of 203 imago, representatives of seven Drosophila species collected from seven localities in Ukraine were screened for Wolbachia via PCR assay. Results. We found Wolbachia infection only in one individual of Drosophila testacea that was collected in the Chornobyl Exclusion Zone. Conclusions. In Ukraine, the examined Drosophila species are characterised by a low prevalence of Wolbachia infection. This research, together with previously reported infections in D. melanogaster and D. simulans populations, indicate that Wolbachia infects 3 out of 9 Drosophila species surveyed in Ukraine

Antarctic bdelloid rotifers: diversity, endemism and evolution

Antarctica is an isolated continent whose conditions challenge the survival of living organisms. High levels of endemism are now known in many Antarctic organisms, including algae, tardigrades, nematodes and microarthropods. Bdelloid rotifers are a key, widespread and abundant group of Antarctic microscopic invertebrates. However, their diversity, regional distribution and endemism have received little attention until recently. We provide the first authoritative review on Antarctic Bdelloidea, based on published data and new collections. Our analysis reveals the extreme levels of bdelloid endemism in Antarctica. Sixty-six bdelloid morphospecies are now confirmed from the continent, and 83–91 putative species are identified using molecular approaches (depending on the delimitation method used). Twelve previously unknown species are described based on both morphology and molecular analyses. Molecular analyses indicate that only two putative species found in Antarctica proved to be truly cosmopolitan. The level of endemism based on the available data set (95%) is higher than that in any other continent, with many bdelloid species occurring only in maritime or continental Antarctica. These findings are consistent with the long-term presence of Bdelloidea in Antarctica, with their considerable isolation facilitating intraregional radiation, providing further evidence that does not support the microbial global ubiquity hypothesis that “everything is everywhere.

Changes in gene DNA methylation and expression networks accompany caste specialization and age-related physiological changes in a social insect

Social insects provide systems for studying epigenetic regulation of phenotypes, particularly with respect to differentiation of reproductive and worker castes, which typically arise from a common genetic background. The role of gene expression in caste specialization has been extensively studied, but the role of DNA methylation remains controversial. Here, we perform well replicated, integrated analyses of DNA methylation and gene expression in brains of an ant (Formica exsecta) with distinct female castes using traditional approaches (tests of differential methylation) combined with a novel approach (analysis of co-expression and co-methylation networks). We found differences in expression and methylation profiles between workers and queens at different life stages, as well as some overlap between DNA methylation and expression at the functional level. Large portions of the transcriptome and methylome are organized into "modules" of genes, some significantly associated with phenotypic traits of castes and developmental stages. Several gene co-expression modules are preserved in co-methylation networks, consistent with possible regulation of caste-specific gene expression by DNA methylation. Surprisingly, brain co-expression modules were highly preserved when compared with a previous study that examined whole-body co-expression patterns in 16 ant species, suggesting that these modules are evolutionarily conserved and for specific functions in various tissues. Altogether, these results suggest that DNA methylation participates in regulation of caste specialization and age-related physiological changes in social insects.Peer reviewe

Assessment of Colobanthus quitensis genetic polymorphism from the Argentine Islands region (maritime Antarctic) by actin, α- and γ-tubulin gene intron analysis

Colobanthus quitensis is one of the two angiosperm plant species commonly spread in the Antarctic. The species has been extensively analyzed at morphological, anatomical and physiological levels, but information regarding its genetic vari-ability remains limited. The aim of the study was to identify molecular genetic differences between C. quitensis populations in one of the Antarctic localities, the Argentine Islands region by estimating the intron length polymorphism of actin, α- and γ-tubulin genes. Samples of C. quitensis from different Antarctic natural populations were collected during the season of the 24th and previous Ukrainian Antarctic expeditions. Total DNA was isolated using the QIAGEN DNeasy Plant Mini Kit. The polymerase chain reaction was carried out with our own degenerate primers. The resulting amplicons were separated and visualized using polyacrylamide gel electrophoresis followed by silver nitrate staining. Molecular genetic analysis of natural populations of C. quitensis was performed using three DNA-marker systems based on the detection of intron length polymor-phism of actin, α- and γ-tubulin genes. A low level of genetic polymorphism of C. quitensis in the studied region by these types of markers was established. By assessing the intron length polymorphism of actin genes of the studied C. quitensis populations it was possible to establish that the populations of Skua Island had unique amplicons characteristic only for this location. This indicates the possibility of further use of the analysis of intron length polymorphism of actin genes for the study of the molecu-lar genetic diversity of the Antarctic pearlwort. At the same time, the results of analysis of the intron length polymorphism of α- and γ-tubulin genes induce selection of more specific primers, taking into account the structure of the C. quitensis genome. C. quitensis in the study region has a low level of genetic variability in intron length polymorphism of actin, α- and γ-tubulin genes. Overall, the results indicate that DNA markers based on gene structure analysis of highly conserved cytoskeletal pro-teins, namely, actin, α- and γ-tubulin, as additional sources of information, can be used for molecular genetic analysis of C. quitensis populations in the Antarctic

First record of the invasive pest Drosophila suzukii in Ukraine indicates multiple sources of invasion

Drosophila suzukii, commonly known as the spotted-wing Drosophila, is an invasive polyphagous fruit pest, which has emerged as a global threat to agriculture in the Americas and in Europe. Due to the rapid spread, great economic losses and its pest behavior, D. suzukii represents a powerful model for invasion biology and pest management studies. However, its current European distribution, invasion routes and levels of genetic diversity in populations of D. suzukii are poorly understood. We present the first report of D. suzukii from Ukraine, with the invasion likely occurring close to 2014. The pattern of genetic variation at cytochrome oxidase I among D. suzukii populations from Europe, USA and Asia reveals comparatively high genetic diversity in the Ukrainian population of this pest species, suggesting a complex invasion scenario from multiple sources. Further monitoring patterns of genetic variation across space and time, to better understand the invasion routes of this invasive insect pest, will be an essential part for developing successful pest management strategies

Drosophila Evolution over Space and Time (DEST): A New Population Genomics Resource

Drosophila melanogaster is a leading model in population genetics and genomics, and a growing number of whole-genome data sets from natural populations of this species have been published over the last years. A major challenge is the integration of disparate data sets, often generated using different sequencing technologies and bioinformatic pipelines, which hampers our ability to address questions about the evolution of this species. Here we address these issues by developing a bioinformatics pipeline that maps pooled sequencing (Pool-Seq) reads from D. melanogaster to a hologenome consisting of fly and symbiont genomes and estimates allele frequencies using either a heuristic (PoolSNP) or a probabilistic variant caller (SNAPE-pooled). We use this pipeline to generate the largest data repository of genomic data available for D. melanogaster to date, encompassing 271 previously published and unpublished population samples from over 100 locations in >20 countries on four continents. Several of these locations have been sampled at different seasons across multiple years. This data set, which we call Drosophila Evolution over Space and Time (DEST), is coupled with sampling and environmental metadata. A web-based genome browser and web portal provide easy access to the SNP data set. We further provide guidelines on how to use Pool-Seq data for model-based demographic inference. Our aim is to provide this scalable platform as a community resource which can be easily extended via future efforts for an even more extensive cosmopolitan data set. Our resource will enable population geneticists to analyze spatiotemporal genetic patterns and evolutionary dynamics of D. melanogaster populations in unprecedented detail.We thank four reviewers and the handling editor for helpful comments on previous versions of our manuscript. We are grateful to the members of the DrosEU and DrosRTEC consortia for their long-standing support, collaboration, and for discussion. DrosEU was funded by a Special Topic Networks (STN) grant from the European Society for Evolutionary Biology (ESEB). M.K. was supported by the Austrian Science Foundation (grant no. FWF P32275); J.G. by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (H2020-ERC-2014-CoG-647900) and by the Spanish Ministry of Science and Innovation (BFU-2011-24397); T.F. by the Swiss National Science Foundation (SNSF grants PP00P3_133641, PP00P3_165836, and 31003A_182262) and a Mercator Fellowship from the German Research Foundation (DFG), held as a EvoPAD Visiting Professor at the Institute for Evolution and Biodiversity, University of Münster; AOB by the National Institutes of Health (R35 GM119686); M.K. by Academy of Finland grant 322980; V.L. by Danish Natural Science Research Council (FNU) (grant no. 4002-00113B); FS Deutsche Forschungsgemeinschaft (DFG) (grant no. STA1154/4-1), Project 408908608; J.P. by the Deutsche Forschungsgemeinschaft Projects 274388701 and 347368302; A.U. by FPI fellowship (BES-2012-052999); ET Israel Science Foundation (ISF) (grant no. 1737/17); M.S.V., M.S.R. and M.J. by a grant from the Ministry of Education, Science and Technological Development of the Republic of Serbia (451-03-68/2020-14/200178); A.P., K.E. and M.T. by a grant from the Ministry of Education, Science and Technological Development of the Republic of Serbia (451-03-68/2020-14/200007); and TM NSERC grant RGPIN-2018-05551. The authors acknowledge Research Computing at The University of Virginia for providing computational resources and technical support that have contributed to the results reported within this publication (https://rc.virginia.edu, last accessed September 6, 2021)