TY - JOUR AB - The role of natural selection in the evolution of adaptive phenotypes has undergone constant probing by evolutionary biologists, employing both theoretical and empirical approaches. As Darwin noted, natural selection can act together with other processes, including random changes in the frequencies of phenotypic differences that are not under strong selection, and changes in the environment, which may reflect evolutionary changes in the organisms themselves. As understanding of genetics developed after 1900, the new genetic discoveries were incorporated into evolutionary biology. The resulting general principles were summarized by Julian Huxley in his 1942 book Evolution: the modern synthesis. Here, we examine how recent advances in genetics, developmental biology and molecular biology, including epigenetics, relate to today's understanding of the evolution of adaptations. We illustrate how careful genetic studies have repeatedly shown that apparently puzzling results in a wide diversity of organisms involve processes that are consistent with neo-Darwinism. They do not support important roles in adaptation for processes such as directed mutation or the inheritance of acquired characters, and therefore no radical revision of our understanding of the mechanism of adaptive evolution is needed. AU - Charlesworth, Deborah AU - Barton, Nicholas H AU - Charlesworth, Brian ID - 953 IS - 1855 JF - Proceedings of the Royal Society of London Series B Biological Sciences TI - The sources of adaptive evolution VL - 284 ER - TY - JOUR AB - A novel strategy for controlling the spread of arboviral diseases such as dengue, Zika and chikungunya is to transform mosquito populations with virus-suppressing Wolbachia. In general, Wolbachia transinfected into mosquitoes induce fitness costs through lower viability or fecundity. These maternally inherited bacteria also produce a frequency-dependent advantage for infected females by inducing cytoplasmic incompatibility (CI), which kills the embryos produced by uninfected females mated to infected males. These competing effects, a frequency-dependent advantage and frequency-independent costs, produce bistable Wolbachia frequency dynamics. Above a threshold frequency, denoted pˆ, CI drives fitness-decreasing Wolbachia transinfections through local populations; but below pˆ, infection frequencies tend to decline to zero. If pˆ is not too high, CI also drives spatial spread once infections become established over sufficiently large areas. We illustrate how simple models provide testable predictions concerning the spatial and temporal dynamics of Wolbachia introductions, focusing on rate of spatial spread, the shape of spreading waves, and the conditions for initiating spread from local introductions. First, we consider the robustness of diffusion-based predictions to incorporating two important features of wMel-Aedes aegypti biology that may be inconsistent with the diffusion approximations, namely fast local dynamics induced by complete CI (i.e., all embryos produced from incompatible crosses die) and long-tailed, non-Gaussian dispersal. With complete CI, our numerical analyses show that long-tailed dispersal changes wave-width predictions only slightly; but it can significantly reduce wave speed relative to the diffusion prediction; it also allows smaller local introductions to initiate spatial spread. Second, we use approximations for pˆ and dispersal distances to predict the outcome of 2013 releases of wMel-infected Aedes aegypti in Cairns, Australia, Third, we describe new data from Ae. aegypti populations near Cairns, Australia that demonstrate long-distance dispersal and provide an approximate lower bound on pˆ for wMel in northeastern Australia. Finally, we apply our analyses to produce operational guidelines for efficient transformation of vector populations over large areas. We demonstrate that even very slow spatial spread, on the order of 10-20 m/month (as predicted), can produce area-wide population transformation within a few years following initial releases covering about 20-30% of the target area. AU - Turelli, Michael AU - Barton, Nicholas H ID - 952 JF - Theoretical Population Biology SN - 00405809 TI - Deploying dengue-suppressing Wolbachia: Robust models predict slow but effective spatial spread in Aedes aegypti VL - 115 ER - TY - JOUR AB - Dengue-suppressing Wolbachia strains are promising tools for arbovirus control, particularly as they have the potential to self-spread following local introductions. To test this, we followed the frequency of the transinfected Wolbachia strain wMel through Ae. aegypti in Cairns, Australia, following releases at 3 nonisolated locations within the city in early 2013. Spatial spread was analysed graphically using interpolation and by fitting a statistical model describing the position and width of the wave. For the larger 2 of the 3 releases (covering 0.97 km2 and 0.52 km2), we observed slow but steady spatial spread, at about 100–200 m per year, roughly consistent with theoretical predictions. In contrast, the smallest release (0.11 km2) produced erratic temporal and spatial dynamics, with little evidence of spread after 2 years. This is consistent with the prediction concerning fitness-decreasing Wolbachia transinfections that a minimum release area is needed to achieve stable local establishment and spread in continuous habitats. Our graphical and likelihood analyses produced broadly consistent estimates of wave speed and wave width. Spread at all sites was spatially heterogeneous, suggesting that environmental heterogeneity will affect large-scale Wolbachia transformations of urban mosquito populations. The persistence and spread of Wolbachia in release areas meeting minimum area requirements indicates the promise of successful large-scale population transfo AU - Schmidt, Tom AU - Barton, Nicholas H AU - Rasic, Gordana AU - Turley, Andrew AU - Montgomery, Brian AU - Iturbe Ormaetxe, Inaki AU - Cook, Peter AU - Ryan, Peter AU - Ritchie, Scott AU - Hoffmann, Ary AU - O’Neill, Scott AU - Turelli, Michael ID - 951 IS - 5 JF - PLoS Biology SN - 15449173 TI - Local introduction and heterogeneous spatial spread of dengue-suppressing Wolbachia through an urban population of Aedes Aegypti VL - 15 ER - TY - GEN AU - Schmidt, Tom AU - Barton, Nicholas H AU - Rasic, Gordana AU - Turley, Andrew AU - Montgomery, Brian AU - Iturbe Ormaetxe, Inaki AU - Cook, Peter AU - Ryan, Peter AU - Ritchie, Scott AU - Hoffmann, Ary AU - O’Neill, Scott AU - Turelli, Michael ID - 9858 TI - Excel file with data on mosquito densities, Wolbachia infection status and housing characteristics ER - TY - GEN AU - Schmidt, Tom AU - Barton, Nicholas H AU - Rasic, Gordana AU - Turley, Andrew AU - Montgomery, Brian AU - Iturbe Ormaetxe, Inaki AU - Cook, Peter AU - Ryan, Peter AU - Ritchie, Scott AU - Hoffmann, Ary AU - O’Neill, Scott AU - Turelli, Michael ID - 9857 TI - Supporting information concerning observed wMel frequencies and analyses of habitat variables ER - TY - GEN AU - Schmidt, Tom AU - Barton, Nicholas H AU - Rasic, Gordana AU - Turley, Andrew AU - Montgomery, Brian AU - Iturbe Ormaetxe, Inaki AU - Cook, Peter AU - Ryan, Peter AU - Ritchie, Scott AU - Hoffmann, Ary AU - O’Neill, Scott AU - Turelli, Michael ID - 9856 TI - Supporting Information concerning additional likelihood analyses and results ER - TY - JOUR AB - Frequency-independent selection is generally considered as a force that acts to reduce the genetic variation in evolving populations, yet rigorous arguments for this idea are scarce. When selection fluctuates in time, it is unclear whether frequency-independent selection may maintain genetic polymorphism without invoking additional mechanisms. We show that constant frequency-independent selection with arbitrary epistasis on a well-mixed haploid population eliminates genetic variation if we assume linkage equilibrium between alleles. To this end, we introduce the notion of frequency-independent selection at the level of alleles, which is sufficient to prove our claim and contains the notion of frequency-independent selection on haploids. When selection and recombination are weak but of the same order, there may be strong linkage disequilibrium; numerical calculations show that stable equilibria are highly unlikely. Using the example of a diallelic two-locus model, we then demonstrate that frequency-independent selection that fluctuates in time can maintain stable polymorphism if linkage disequilibrium changes its sign periodically. We put our findings in the context of results from the existing literature and point out those scenarios in which the possible role of frequency-independent selection in maintaining genetic variation remains unclear. AU - Novak, Sebastian AU - Barton, Nicholas H ID - 910 IS - 2 JF - Genetics TI - When does frequency-independent selection maintain genetic variation? VL - 207 ER - TY - JOUR AB - Moths and butterflies (Lepidoptera) usually have a pair of differentiated WZ sex chromosomes. However, in most lineages outside of the division Ditrysia, as well as in the sister order Trichoptera, females lack a W chromosome. The W is therefore thought to have been acquired secondarily. Here we compare the genomes of three Lepidoptera species (one Dytrisia and two non-Dytrisia) to test three models accounting for the origin of the W: (1) a Z-autosome fusion; (2) a sex chromosome turnover; and (3) a non-canonical mechanism (e.g., through the recruitment of a B chromosome). We show that the gene content of the Z is highly conserved across Lepidoptera (rejecting a sex chromosome turnover) and that very few genes moved onto the Z in the common ancestor of the Ditrysia (arguing against a Z-autosome fusion). Our comparative genomics analysis therefore supports the secondary acquisition of the Lepidoptera W by a non-canonical mechanism, and it confirms the extreme stability of well-differentiated sex chromosomes. AU - Fraisse, Christelle AU - Picard, Marion A AU - Vicoso, Beatriz ID - 614 IS - 1 JF - Nature Communications SN - 20411723 TI - The deep conservation of the Lepidoptera Z chromosome suggests a non canonical origin of the W VL - 8 ER - TY - DATA AB - The de novo genome assemblies generated for this study, and the associated metadata. AU - Fraisse, Christelle ID - 7163 TI - Supplementary Files for "The deep conservation of the Lepidoptera Z chromosome suggests a non canonical origin of the W" ER - TY - JOUR AB - Mutator strains are expected to evolve when the availability and effect of beneficial mutations are high enough to counteract the disadvantage from deleterious mutations that will inevitably accumulate. As the population becomes more adapted to its environment, both availability and effect of beneficial mutations necessarily decrease and mutation rates are predicted to decrease. It has been shown that certain molecular mechanisms can lead to increased mutation rates when the organism finds itself in a stressful environment. While this may be a correlated response to other functions, it could also be an adaptive mechanism, raising mutation rates only when it is most advantageous. Here, we use a mathematical model to investigate the plausibility of the adaptive hypothesis. We show that such a mechanism can be mantained if the population is subjected to diverse stresses. By simulating various antibiotic treatment schemes, we find that combination treatments can reduce the effectiveness of second-order selection on stress-induced mutagenesis. We discuss the implications of our results to strategies of antibiotic therapy. AU - Lukacisinova, Marta AU - Novak, Sebastian AU - Paixao, Tiago ID - 696 IS - 7 JF - PLoS Computational Biology SN - 1553734X TI - Stress induced mutagenesis: Stress diversity facilitates the persistence of mutator genes VL - 13 ER -