We report here genome sequences and comparative analyses of three closely related parasitoid wasps: Nasonia vitripennis, N. giraulti, and N. longicornis. Parasitoids are important regulators of arthropod populations, including major agricultural pests and disease vectors, and Nasonia is an emerging genetic model, particularly for evolutionary and developmental genetics. Key findings include the identification of a functional DNA methylation tool kit; hymenopteran-specific genes including diverse venoms; lateral gene transfers among Pox viruses, Wolbachia, and Nasonia; and the rapid evolution of genes involved in nuclear-mitochondrial interactions that are implicated in speciation. Newly developed genome resources advance Nasonia for genetic research, accelerate mapping and cloning of quantitative trait loci, and will ultimately provide tools and knowledge for further increasing the utility of parasitoids as pest insect-control agents.

B chromosomes are extra chromosomes to the standard complement that occur in many organisms. They can originate in a number of ways including derivation from autosomes and sex chromosomes in intra- and interspecies crosses. Their subsequent molecular evolution resembles that of univalent sex chromosomes, which involves gene silencing, heterochromatinization and the accumulation of repetitive DNA and transposons. B-chromosome frequencies in populations result from a balance between their transmission rates and their effects on host fitness. Their long-term evolution is considered to be the outcome of selection on the host genome to eliminate B chromosomes or suppress their effects and on the B chromosome's ability to escape through the generation of new variants. Because B chromosomes interact with the standard chromosomes, they can play an important role in genome evolution and may be useful for studying molecular evolutionary processes.

Sexual reproduction is a fundamental aspect of life. It is defined by the occurrence of meiosis and the fusion of two gametes of different sexes or mating types. Genetic mechanisms for the determination and differentiation of the two sexes are diverse and evolutionary labile. This book synthesizes the contemporary literature on patterns and processes of sex determination evolution. The first chapter introduces definitions and concepts of sexual reproduction. Chapter 2 provides a comprehensive classification of sex-determination systems and describes the diversity of sexual cycles across eukaryote lineages, from excavates to mammals. Subsequent chapters detail the molecular mechanisms and quantitative genetics of sex determination (Chapters 3 and 4), examine the processes of sex-chromosome evolution (Chapter 5), and discuss life-history consequences of sex-determination systems (Chapter 6). The final chapter addresses the evolutionary processes responsible for the diversity and turnover in sex determination (Chapter 7). The book provides an overview of different sex-determination systems and details of its molecular regulation in fungi, plants, and animals, many of which are covered in separate text boxes and figures. It is argued that sex determination and primary sex differentiation cannot be regarded as separate processes and that the traditional dichotomous view of genotypic (GSD) and environmental (ESD) sex determination is no longer accurate. Ample documentation is provided about how sex determination affects, and is affected by, various forms of sexual conflict, sexual selection, and speciation. The book makes clear that sex-determination evolution will remain a highly dynamic field of research in the future.

BackgroundAdult house flies, Musca domestica L., are mechanical vectors of more than 100 devastating diseases that have severe consequences for human and animal health. House fly larvae play a vital role as decomposers of animal wastes, and thus live in intimate association with many animal pathogens.ResultsWe have sequenced and analyzed the genome of the house fly using DNA from female flies. The sequenced genome is 691 Mb. Compared with Drosophila melanogaster, the genome contains a rich resource of shared and novel protein coding genes, a significantly higher amount of repetitive elements, and substantial increases in copy number and diversity of both the recognition and effector components of the immune system, consistent with life in a pathogen-rich environment. There are 146 P450 genes, plus 11 pseudogenes, in M. domestica, representing a significant increase relative to D. melanogaster and suggesting the presence of enhanced detoxification in house flies. Relative to D. melanogaster, M. domestica has also evolved an expanded repertoire of chemoreceptors and odorant binding proteins, many associated with gustation.ConclusionsThis represents the first genome sequence of an insect that lives in intimate association with abundant animal pathogens. The house fly genome provides a rich resource for enabling work on innovative methods of insect control, for understanding the mechanisms of insecticide resistance, genetic adaptation to high pathogen loads, and for exploring the basic biology of this important pest. The genome of this species will also serve as a close out-group to Drosophila in comparative genomic studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-014-0466-3) contains supplementary material, which is available to authorized users.

The Wasps and the Bees Sex development in bees and wasps depends on whether or not they develop from a haploid unfertilized egg (resulting in males) or diploid fertilized egg (resulting in females). Although these ploidy-level developmental processes are conserved among bees and wasps, the mechanisms that direct development down a male or female pathway differ significantly. By examining the sex-determining genes in the parasitoid wasp Nasonia , Verhulst et al. (p. 620 ) have shown that a maternal messenger RNA (mRNA) is necessary to initiate the female pathway. The mRNA operates in combination with conserved maternal and paternal genes to produce females, which explains why females are diploids. In unfertilized eggs, maternal provisioning of the gene transcript is too low to initiate the female pathway.