Male-killing bacteria in insects: mechanisms, incidence and implications

Bacteria that are vertically transmitted through female hosts and kill male hosts that inherit them were first recorded in insects during the 1950s. Recent studies have shown these "male-killers" to be diverse and have led to a reappraisal of the biology of many groups of bacteria. Rickettsia, for instance, have been regarded as human pathogens transmitted by arthropods. The finding of a male-killing Rickettsia obligately associated with an insect suggests that the genus' members may be primarily associated with arthropods and are only sometimes pathogens of vertebrates. We examined both how killing of male hosts affects the dynamics of inherited bacteria and how male-killing bacteria affect their host populations. Finally, we assessed the potential use of these microorganisms in the control of insect populations

The SLIM (Social learning for the integrated management and sustainable use of water at catchment scale) Final Report

Background: SLIM stands for 'Socuak Learning for the Integrated Management and Sustainable Use of Water at Catchment Scale'. It is a multi-country research project funded by the European Commission (DG RESEARCH - 5th Framework Programme for research and technological development, 1998-2002). Its main theme is the investigation of the socio-economic aspects of the sustainable use of water. Within this theme, its main focus of interest lies in understanding the application of social learning as a conceptual framework, an operational principle, a policy instrument and a process of systemic change

Transforming Science into Practice

The space for action that might move agricultural systems toward sustainability is narrowing. In so far as increasing dis-order in agroecosystems and food systems is caused by human agency, then remedial action must take account of cognition. This article argues that an understanding of cognitive processes is essential, as the foundation for participatory R, D & E that builds platforms of cooperation, binding actors into communities of learning that are trasnforming both science and practice

The ecology and genetics of speciation in Heliconius butterflies (Lepidoptera: Nymphalidae)

Natural hybridisation between species offers an opportunity to study the processes of speciation. This thesis describes a study of hybridisation between Heliconius himera, which is endemic to dry forest in southern Ecuador and northern Peru, and H. erato, which is ubiquitous in wet forest throughout the neotropics. In a zone of contact in southern Ecuador hybrids are found at low frequency. Collections show that the contact zone is about 5 km wide, half the width of the narrowest clines between colour pattern races of H. erato, which implies that strong selection is maintaining the parapatric distributions of the species. Polymorphic protein and mitochondrial DNA markers were used to examine patterns of genetic differentiation and gene flow across the hybrid zone. Marked genetic differences between himera and erato are maintained in sympatry. Furthermore, analysis of linkage relationships between the allozyme markers showed that species differences are distributed widely across the genome. There was no evidence for any divergence in host plant ecology, but the hybrid zone between himera and erato was closely correlated with a habitat transition from wet to dry forest. Experiments showed that the barrier to gene flow was mainly due to strong assortative mating between himera and erato. Hybrid crosses showed no reduction in viability or fertility. Analysis of these broods showed that major gene control of pattern elements is similar to that found in previous studies of H. erato races, and the loci are homologous. Another species, H. charitonia, also has a genetically distinct sister species in the dry forests of Ecuador and Peru, peruviana. In both taxa, speciation is associated with divergence in habitat and warning colour, and in the case of himera and erato at least, there is a change in mating preferences but no evidence for genomic incompatibilities

Flies on the move: an inherited virus mirrors Drosophila melanogaster's elusive ecology and demography.

Journal ArticleResearch Support, Non-U.S. Gov'tCopyright © 2014 John Wiley & Sons LtdThis is the accepted version of the following article: Wilfert, L. and Jiggins, F. M. (2014), Flies on the move: an inherited virus mirrors Drosophila melanogaster's elusive ecology and demography. Molecular Ecology, 23: 2093–2104. doi: 10.1111/mec.12709, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/mec.12709/abstractVertically transmitted parasites rely on their host's reproduction for their transmission, leading to the evolutionary histories of both parties being intimately entwined. Parasites can thus serve as a population genetic magnifying glass for their host's demographic history. Here, we study the fruitfly Drosophila melanogaster's vertically transmitted sigma virus DMelSV. The virus has a high mutation rate and low effective population size, allowing us to reconstruct at a fine scale how the combined forces of the movement of flies and selection on the virus have shaped its migration patterns. We found that the virus is likely to have spread to Europe from Africa, mirroring the colonization route of Drosophila. The North American DMelSV population appears to be the result of a recent single immigration from Europe, invading together with its host in the late 19th century. Across Europe, DMelSV migration rates are low and populations are highly genetically structured, likely reflecting limited fly movement. Despite being intolerant of extreme cold, viral diversity suggests that fly populations can persist in harsh continental climates and that recolonization from the warmer south plays a minor role. In conclusion, studying DMelSV can provide insights into the poorly understood ecology of D. melanogaster, one of the best-studied organisms in biology.Leverhulme TrustRoyal Society University Research Fellowshi

Comparative Genomics Reveals the Origins and Diversity of Arthropod Immune Systems.

Insects are an important model for the study of innate immune systems, but remarkably little is known about the immune system of other arthropod groups despite their importance as disease vectors, pests, and components of biological diversity. Using comparative genomics, we have characterized the immune system of all the major groups of arthropods beyond insects for the first time--studying five chelicerates, a myriapod, and a crustacean. We found clear traces of an ancient origin of innate immunity, with some arthropods having Toll-like receptors and C3-complement factors that are more closely related in sequence or structure to vertebrates than other arthropods. Across the arthropods some components of the immune system, such as the Toll signaling pathway, are highly conserved. However, there is also remarkable diversity. The chelicerates apparently lack the Imd signaling pathway and beta-1,3 glucan binding proteins--a key class of pathogen recognition receptors. Many genes have large copy number variation across species, and this may sometimes be accompanied by changes in function. For example, we find that peptidoglycan recognition proteins have frequently lost their catalytic activity and switch between secreted and intracellular forms. We also find that there has been widespread and extensive duplication of the cellular immune receptor Dscam (Down syndrome cell adhesion molecule), which may be an alternative way to generate the high diversity produced by alternative splicing in insects. In the antiviral short interfering RNAi pathway Argonaute 2 evolves rapidly and is frequently duplicated, with a highly variable copy number. Our results provide a detailed analysis of the immune systems of several important groups of animals for the first time and lay the foundations for functional work on these groups.This project was funded by a Royal Society University Research Fellowship and a European Research Council grant DrosophilaInfection (281668) to F.M.J., and a Medical Research Council studentship to W.J.P.This is the final published version. It first appeared at http://mbe.oxfordjournals.org/content/early/2015/05/12/molbev.msv093.long