@article{21985, abstract = {Upon infecting a bacterial cell, temperate phages make a decision between lysis and lysogeny. While research has previously explored how phages sense environmental information to make this choice, most studies have focused on modelling known mechanisms that impact the decision. These mechanisms tell us what environmental information the phage does respond to, but not what it should respond to, as the signals sensed by the phage may serve as proxies for other sources of information. Here, using a mechanism-agnostic population dynamics model, we find that irreversible phage binding to lysogens protects sensitive host cells from infection. This results in lysogens being an additional environmental factor that the phage should sense while making its decision to undergo lysis or lysogeny. Using this model, we derive a responsive lysogeny probability for phages that respond to both cell and lysogen densities optimized towards invading phage-occupied systems, and show that it is more capable of invading and resisting invasion than phage with fixed lysogeny probabilities across different environmental conditions.}, author = {Wu, Bryan and Guet, Calin C}, issn = {1558-5646}, journal = {Evolution}, number = {6}, pages = {1365--1373}, publisher = {Oxford University Press}, title = {{Responsive lysogeny under nonproductive phage binding}}, doi = {10.1093/evolut/qpag061}, volume = {80}, year = {2026}, } @article{19876, abstract = {Assortative mating and sexual selection are widespread in nature and can play an important role in speciation by facilitating the buildup and maintenance of reproductive isolation (RI). However, their contribution to genome-wide suppression of gene flow during RI is rarely quantified. Here, we consider a polygenic “magic” trait that is divergently selected across two populations connected by migration, while also serving as the basis of assortative mating, thus generating sexual selection on one or both sexes. We obtain theoretical predictions for divergence at individual trait loci by assuming that the effect of all other loci on any locus can be encapsulated via an effective migration rate, which bears a simple relationship to measurable fitness components of migrants and various early-generation hybrids. Our analysis clarifies how “tipping points” (characterized by an abrupt collapse of adaptive divergence) arise, and when assortative mating can shift the critical level of migration beyond which divergence collapses. We quantify the relative contributions of viability and sexual selection to genome-wide barriers to gene flow and discuss how these depend on existing divergence levels. Our results suggest that effective migration rates provide a useful way of understanding genomic divergence, even in scenarios involving multiple, interacting mechanisms of RI. }, author = {Surendranadh, Parvathy and Sachdeva, Himani}, issn = {1558-5646}, journal = {Evolution}, number = {7}, pages = {1185--1198}, publisher = {Oxford University Press}, title = {{Effect of assortative mating and sexual selection on polygenic barriers to gene flow}}, doi = {10.1093/evolut/qpaf047}, volume = {79}, year = {2025}, } @article{20044, abstract = {Genetic trade-offs—which occur when variants that are beneficial in some contexts of natural selection are harmful in others—can influence a wide range of evolutionary phenomena, from the maintenance of genetic variation to the evolution of aging and sex differences. An extensive body of evolutionary theory has focused on the consequences of such trade-offs, and recent analyses of Fisher’s geometric model have further quantified the expected proportion of new mutations that exhibit trade-offs. However, the theory remains silent regarding the prevalence of trade-offs among the variants that contribute to adaptation. Here, we extend Fisher’s geometric model to predict the prevalence of trade-offs among the adaptive mutations that become established or fixed in a population. We consider trade-offs between sexes, habitats, fitness components, and temporally fluctuating environments. In all 4 scenarios, trade-off alleles are consistently under-represented among established relative to new beneficial mutations—an effect that arises from the greater susceptibility of trade-off alleles to genetic drift. Adaptation during a population size decline exacerbates this deficit of trade-offs among established mutations, whereas population expansions dampen it. Consequently, threatened populations should primarily adapt using unconditionally beneficial alleles, while invasive populations are more prone to adaptation using variants that exhibit trade-offs.}, author = {Connallon, Tim and Czuppon, Peter and Olito, Colin and Goedert, Debora and Kokko, Hanna and Nava-Bolaños, Angela and Nilén, Sofie and Svensson, Erik I and Zwoinska, Martyna and Dutoit, Ludovic and Ruzicka, Filip}, issn = {1558-5646}, journal = {Evolution}, number = {7}, pages = {1243--1255}, publisher = {Oxford University Press}, title = {{Predicting the prevalence of genetic trade-offs among adaptive substitutions}}, doi = {10.1093/evolut/qpaf061}, volume = {79}, year = {2025}, } @article{20531, abstract = {Genetic drift is potentially an important component of selection for sex, as it is a source of statistical associations between alleles at selected loci. By increasing local drift, population structure may thus amplify the evolutionary advantage of sex. However, most previous models have focused either on haploid populations or on diploid populations without spatial structure. In this article, we use two- and three-locus analytical models and multilocus simulations to explore selection for sex in a diploid population structured according to the island model, in the presence of recurrent deleterious mutations. Our results show that selection generally favors an intermediate rate of sex that decreases as the direct cost of sex increases and increases moderately as the degree of population structure increases. Selection for sex is generated by multiple effects involving genetic associations within and between loci. When selection occurs at many loci, it is generally dominated by interference effects involving deleterious alleles at different loci, captured by our three-locus model. In our multilocus simulations, we observed an irreversible spread of asexual mutants under strong costs of sex, and when deleterious mutations are partially recessive. However, population structure may prevent this spread of asexual mutants when dispersal rates are sufficiently small.}, author = {Fouqueau, Louise and Roze, Denis}, issn = {1558-5646}, journal = {Evolution}, number = {10}, pages = {2167--2180}, publisher = {Oxford University Press}, title = {{Deleterious mutations and selection for sex in spatially structured, diploid populations}}, doi = {10.1093/evolut/qpaf143}, volume = {79}, year = {2025}, } @article{18307, abstract = {Vaccination is the most effective tool to control infectious diseases. However, the evolution of vaccine resistance, exemplified by vaccine resistance in SARS-CoV-2, remains a concern. Here, we model complex vaccination strategies against a pathogen with multiple epitopes—molecules targeted by the vaccine. We found that a vaccine targeting one epitope was ineffective in preventing vaccine escape. Vaccine resistance in highly infectious pathogens was prevented by the full-epitope vaccine, that is, one targeting all available epitopes, but only when the rate of pathogen evolution was low. Strikingly, a bet-hedging strategy of random administration of vaccines targeting different epitopes was the most effective in preventing vaccine resistance in pathogens with the low rate of infection and high rate of evolution. Thus, complex vaccination strategies, when biologically feasible, may be preferable to the currently used single-vaccine approaches for long-term control of disease outbreaks, especially when applied to livestock with near 100% vaccination rates.}, author = {Rella, Simon and Kulikova, Yuliya A. and Minnegalieva, Aygul and Kondrashov, Fyodor}, issn = {1558-5646}, journal = {Evolution: International journal of organic evolution}, number = {10}, pages = {1722--1738}, publisher = {Oxford University Press}, title = {{Complex vaccination strategies prevent the emergence of vaccine resistance}}, doi = {10.1093/evolut/qpae106}, volume = {78}, year = {2024}, } @article{12514, abstract = {The concept of a “speciation continuum” has gained popularity in recent decades. It emphasizes speciation as a continuous process that may be studied by comparing contemporary population pairs that show differing levels of divergence. In their recent perspective article in Evolution, Stankowski and Ravinet provided a valuable service by formally defining the speciation continuum as a continuum of reproductive isolation, based on opinions gathered from a survey of speciation researchers. While we agree that the speciation continuum has been a useful concept to advance the understanding of the speciation process, some intrinsic limitations exist. Here, we advocate for a multivariate extension, the speciation hypercube, first proposed by Dieckmann et al. in 2004, but rarely used since. We extend the idea of the speciation cube and suggest it has strong conceptual and practical advantages over a one-dimensional model. We illustrate how the speciation hypercube can be used to visualize and compare different speciation trajectories, providing new insights into the processes and mechanisms of speciation. A key strength of the speciation hypercube is that it provides a unifying framework for speciation research, as it allows questions from apparently disparate subfields to be addressed in a single conceptual model.}, author = {Bolnick, Daniel I. and Hund, Amanda K. and Nosil, Patrik and Peng, Foen and Ravinet, Mark and Stankowski, Sean and Subramanian, Swapna and Wolf, Jochen B.W. and Yukilevich, Roman}, issn = {1558-5646}, journal = {Evolution: International journal of organic evolution}, number = {1}, pages = {318--328}, publisher = {Oxford University Press}, title = {{A multivariate view of the speciation continuum}}, doi = {10.1093/evolut/qpac004}, volume = {77}, year = {2023}, } @article{14604, abstract = {Sex chromosomes have evolved independently multiple times, but why some are conserved for more than 100 million years whereas others turnover rapidly remains an open question. Here, we examine the homology of sex chromosomes across nine orders of insects, plus the outgroup springtails. We find that the X chromosome is likely homologous across insects and springtails; the only exception is in the Lepidoptera, which has lost the X and now has a ZZ/ZW sex-chromosome system. These results suggest the ancestral insect X chromosome has persisted for more than 450 million years—the oldest known sex chromosome to date. Further, we propose that the shrinking of gene content the dipteran X chromosome has allowed for a burst of sex-chromosome turnover that is absent from other speciose insect orders.}, author = {Toups, Melissa A and Vicoso, Beatriz}, issn = {1558-5646}, journal = {Evolution}, number = {11}, pages = {2504--2511}, publisher = {Oxford University Press}, title = {{The X chromosome of insects likely predates the origin of class Insecta}}, doi = {10.1093/evolut/qpad169}, volume = {77}, year = {2023}, } @article{11334, abstract = {Hybridization is a common evolutionary process with multiple possible outcomes. In vertebrates, interspecific hybridization has repeatedly generated parthenogenetic hybrid species. However, it is unknown whether the generation of parthenogenetic hybrids is a rare outcome of frequent hybridization between sexual species within a genus or the typical outcome of rare hybridization events. Darevskia is a genus of rock lizards with both hybrid parthenogenetic and sexual species. Using capture sequencing, we estimate phylogenetic relationships and gene flow among the sexual species, to determine how introgressive hybridization relates to the origins of parthenogenetic hybrids. We find evidence for widespread hybridization with gene flow, both between recently diverged species and deep branches. Surprisingly, we find no signal of gene flow between parental species of the parthenogenetic hybrids, suggesting that the parental pairs were either reproductively or geographically isolated early in their divergence. The generation of parthenogenetic hybrids in Darevskia is, then, a rare outcome of the total occurrence of hybridization within the genus, but the typical outcome when specific species pairs hybridize. Our results question the conventional view that parthenogenetic lineages are generated by hybridization in a window of divergence. Instead, they suggest that some lineages possess specific properties that underpin successful parthenogenetic reproduction.}, author = {Freitas, Susana and Westram, Anja M and Schwander, Tanja and Arakelyan, Marine and Ilgaz, Çetin and Kumlutas, Yusuf and Harris, David James and Carretero, Miguel A. and Butlin, Roger K.}, issn = {1558-5646}, journal = {Evolution}, number = {5}, pages = {899--914}, publisher = {Wiley}, title = {{Parthenogenesis in Darevskia lizards: A rare outcome of common hybridization, not a common outcome of rare hybridization}}, doi = {10.1111/evo.14462}, volume = {76}, year = {2022}, } @article{12234, abstract = {Hybrid speciation—the origin of new species resulting from the hybridization of genetically divergent lineages—was once considered rare, but genomic data suggest that it may occur more often than once thought. In this study, Noguerales and Ortego found genomic evidence supporting the hybrid origin of a grasshopper that is able to exploit a broader range of host plants than either of its putative parents.}, author = {Stankowski, Sean}, issn = {1558-5646}, journal = {Evolution}, keywords = {General Agricultural and Biological Sciences, Genetics, Ecology, Evolution, Behavior and Systematics}, number = {11}, pages = {2784--2785}, publisher = {Wiley}, title = {{Digest: On the origin of a possible hybrid species}}, doi = {10.1111/evo.14632}, volume = {76}, year = {2022}, } @article{12247, abstract = {Chromosomal inversions have been shown to play a major role in a local adaptation by suppressing recombination between alternative arrangements and maintaining beneficial allele combinations. However, so far, their importance relative to the remaining genome remains largely unknown. Understanding the genetic architecture of adaptation requires better estimates of how loci of different effect sizes contribute to phenotypic variation. Here, we used three Swedish islands where the marine snail Littorina saxatilis has repeatedly evolved into two distinct ecotypes along a habitat transition. We estimated the contribution of inversion polymorphisms to phenotypic divergence while controlling for polygenic effects in the remaining genome using a quantitative genetics framework. We confirmed the importance of inversions but showed that contributions of loci outside inversions are of similar magnitude, with variable proportions dependent on the trait and the population. Some inversions showed consistent effects across all sites, whereas others exhibited site-specific effects, indicating that the genomic basis for replicated phenotypic divergence is only partly shared. The contributions of sexual dimorphism as well as environmental factors to phenotypic variation were significant but minor compared to inversions and polygenic background. Overall, this integrated approach provides insight into the multiple mechanisms contributing to parallel phenotypic divergence.}, author = {Koch, Eva L. and Ravinet, Mark and Westram, Anja M and Johannesson, Kerstin and Butlin, Roger K.}, issn = {1558-5646}, journal = {Evolution}, keywords = {General Agricultural and Biological Sciences, Genetics, Ecology, Evolution, Behavior and Systematics}, number = {10}, pages = {2332--2346}, publisher = {Wiley}, title = {{Genetic architecture of repeated phenotypic divergence in Littorina saxatilis evolution}}, doi = {10.1111/evo.14602}, volume = {76}, year = {2022}, } @article{8743, abstract = {Montane cloud forests are areas of high endemism, and are one of the more vulnerable terrestrial ecosystems to climate change. Thus, understanding how they both contribute to the generation of biodiversity, and will respond to ongoing climate change, are important and related challenges. The widely accepted model for montane cloud forest dynamics involves upslope forcing of their range limits with global climate warming. However, limited climate data provides some support for an alternative model, where range limits are forced downslope with climate warming. Testing between these two models is challenging, due to the inherent limitations of climate and pollen records. We overcome this with an alternative source of historical information, testing between competing model predictions using genomic data and demographic analyses for a species of beetle tightly associated to an oceanic island cloud forest. Results unequivocally support the alternative model: populations that were isolated at higher elevation peaks during the Last Glacial Maximum are now in contact and hybridizing at lower elevations. Our results suggest that genomic data are a rich source of information to further understand how montane cloud forest biodiversity originates, and how it is likely to be impacted by ongoing climate change.}, author = {Salces-Castellano, Antonia and Stankowski, Sean and Arribas, Paula and Patino, Jairo and Karger, Dirk N. and Butlin, Roger and Emerson, Brent C.}, issn = {1558-5646}, journal = {Evolution}, number = {2}, pages = {231--244}, publisher = {Wiley}, title = {{Long-term cloud forest response to climate warming revealed by insect speciation history}}, doi = {10.1111/evo.14111}, volume = {75}, year = {2021}, } @article{9252, abstract = {This paper analyses the conditions for local adaptation in a metapopulation with infinitely many islands under a model of hard selection, where population size depends on local fitness. Each island belongs to one of two distinct ecological niches or habitats. Fitness is influenced by an additive trait which is under habitat‐dependent directional selection. Our analysis is based on the diffusion approximation and accounts for both genetic drift and demographic stochasticity. By neglecting linkage disequilibria, it yields the joint distribution of allele frequencies and population size on each island. We find that under hard selection, the conditions for local adaptation in a rare habitat are more restrictive for more polygenic traits: even moderate migration load per locus at very many loci is sufficient for population sizes to decline. This further reduces the efficacy of selection at individual loci due to increased drift and because smaller populations are more prone to swamping due to migration, causing a positive feedback between increasing maladaptation and declining population sizes. Our analysis also highlights the importance of demographic stochasticity, which exacerbates the decline in numbers of maladapted populations, leading to population collapse in the rare habitat at significantly lower migration than predicted by deterministic arguments.}, author = {Szep, Eniko and Sachdeva, Himani and Barton, Nicholas H}, issn = {1558-5646}, journal = {Evolution}, keywords = {Genetics, Ecology, Evolution, Behavior and Systematics, General Agricultural and Biological Sciences}, number = {5}, pages = {1030--1045}, publisher = {Wiley}, title = {{Polygenic local adaptation in metapopulations: A stochastic eco‐evolutionary model}}, doi = {10.1111/evo.14210}, volume = {75}, year = {2021}, } @article{9374, abstract = {If there are no constraints on the process of speciation, then the number of species might be expected to match the number of available niches and this number might be indefinitely large. One possible constraint is the opportunity for allopatric divergence. In 1981, Felsenstein used a simple and elegant model to ask if there might also be genetic constraints. He showed that progress towards speciation could be described by the build‐up of linkage disequilibrium among divergently selected loci and between these loci and those contributing to other forms of reproductive isolation. Therefore, speciation is opposed by recombination, because it tends to break down linkage disequilibria. Felsenstein then introduced a crucial distinction between “two‐allele” models, which are subject to this effect, and “one‐allele” models, which are free from the recombination constraint. These fundamentally important insights have been the foundation for both empirical and theoretical studies of speciation ever since.}, author = {Butlin, Roger K. and Servedio, Maria R. and Smadja, Carole M. and Bank, Claudia and Barton, Nicholas H and Flaxman, Samuel M. and Giraud, Tatiana and Hopkins, Robin and Larson, Erica L. and Maan, Martine E. and Meier, Joana and Merrill, Richard and Noor, Mohamed A. F. and Ortiz‐Barrientos, Daniel and Qvarnström, Anna}, issn = {1558-5646}, journal = {Evolution}, keywords = {Genetics, Ecology, Evolution, Behavior and Systematics, General Agricultural and Biological Sciences}, number = {5}, pages = {978--988}, publisher = {Wiley}, title = {{Homage to Felsenstein 1981, or why are there so few/many species?}}, doi = {10.1111/evo.14235}, volume = {75}, year = {2021}, } @article{9383, abstract = {A primary roadblock to our understanding of speciation is that it usually occurs over a timeframe that is too long to study from start to finish. The idea of a speciation continuum provides something of a solution to this problem; rather than observing the entire process, we can simply reconstruct it from the multitude of speciation events that surround us. But what do we really mean when we talk about the speciation continuum, and can it really help us understand speciation? We explored these questions using a literature review and online survey of speciation researchers. Although most researchers were familiar with the concept and thought it was useful, our survey revealed extensive disagreement about what the speciation continuum actually tells us. This is due partly to the lack of a clear definition. Here, we provide an explicit definition that is compatible with the Biological Species Concept. That is, the speciation continuum is a continuum of reproductive isolation. After outlining the logic of the definition in light of alternatives, we explain why attempts to reconstruct the speciation process from present‐day populations will ultimately fail. We then outline how we think the speciation continuum concept can continue to act as a foundation for understanding the continuum of reproductive isolation that surrounds us.}, author = {Stankowski, Sean and Ravinet, Mark}, issn = {1558-5646}, journal = {Evolution}, number = {6}, pages = {1256--1273}, publisher = {Oxford University Press}, title = {{Defining the speciation continuum}}, doi = {10.1111/evo.14215}, volume = {75}, year = {2021}, } @article{7995, abstract = {When divergent populations are connected by gene flow, the establishment of complete reproductive isolation usually requires the joint action of multiple barrier effects. One example where multiple barrier effects are coupled consists of a single trait that is under divergent natural selection and also mediates assortative mating. Such multiple‐effect traits can strongly reduce gene flow. However, there are few cases where patterns of assortative mating have been described quantitatively and their impact on gene flow has been determined. Two ecotypes of the coastal marine snail, Littorina saxatilis , occur in North Atlantic rocky‐shore habitats dominated by either crab predation or wave action. There is evidence for divergent natural selection acting on size, and size‐assortative mating has previously been documented. Here, we analyze the mating pattern in L. saxatilis with respect to size in intensively sampled transects across boundaries between the habitats. We show that the mating pattern is mostly conserved between ecotypes and that it generates both assortment and directional sexual selection for small male size. Using simulations, we show that the mating pattern can contribute to reproductive isolation between ecotypes but the barrier to gene flow is likely strengthened more by sexual selection than by assortment.}, author = {Perini, Samuel and Rafajlović, Marina and Westram, Anja M and Johannesson, Kerstin and Butlin, Roger K.}, issn = {1558-5646}, journal = {Evolution}, number = {7}, pages = {1482--1497}, publisher = {Wiley}, title = {{Assortative mating, sexual selection, and their consequences for gene flow in Littorina}}, doi = {10.1111/evo.14027}, volume = {74}, year = {2020}, } @article{6680, abstract = {This paper analyzes how partial selfing in a large source population influences its ability to colonize a new habitat via the introduction of a few founder individuals. Founders experience inbreeding depression due to partially recessive deleterious alleles as well as maladaptation to the new environment due to selection on a large number of additive loci. I first introduce a simplified version of the Inbreeding History Model (Kelly, 2007) in order to characterize mutation‐selection balance in a large, partially selfing source population under selection involving multiple non‐identical loci. I then use individual‐based simulations to study the eco‐evolutionary dynamics of founders establishing in the new habitat under a model of hard selection. The study explores how selfing rate shapes establishment probabilities of founders via effects on both inbreeding depression and adaptability to the new environment, and also distinguishes the effects of selfing on the initial fitness of founders from its effects on the long‐term adaptive response of the populations they found. A high rate of (but not complete) selfing is found to aid establishment over a wide range of parameters, even in the absence of mate limitation. The sensitivity of the results to assumptions about the nature of polygenic selection are discussed.}, author = {Sachdeva, Himani}, issn = {1558-5646}, journal = {Evolution}, number = {9}, pages = {1729--1745}, publisher = {Wiley}, title = {{Effect of partial selfing and polygenic selection on establishment in a new habitat}}, doi = {10.1111/evo.13812}, volume = {73}, year = {2019}, } @article{1851, abstract = {We consider mating strategies for females who search for males sequentially during a season of limited length. We show that the best strategy rejects a given male type if encountered before a time-threshold but accepts him after. For frequency-independent benefits, we obtain the optimal time-thresholds explicitly for both discrete and continuous distributions of males, and allow for mistakes being made in assessing the correct male type. When the benefits are indirect (genes for the offspring) and the population is under frequency-dependent ecological selection, the benefits depend on the mating strategy of other females as well. This case is particularly relevant to speciation models that seek to explore the stability of reproductive isolation by assortative mating under frequency-dependent ecological selection. We show that the indirect benefits are to be quantified by the reproductive values of couples, and describe how the evolutionarily stable time-thresholds can be found. We conclude with an example based on the Levene model, in which we analyze the evolutionarily stable assortative mating strategies and the strength of reproductive isolation provided by them.}, author = {Priklopil, Tadeas and Kisdi, Eva and Gyllenberg, Mats}, issn = {1558-5646}, journal = {Evolution}, number = {4}, pages = {1015 -- 1026}, publisher = {Wiley}, title = {{Evolutionarily stable mating decisions for sequentially searching females and the stability of reproductive isolation by assortative mating}}, doi = {10.1111/evo.12618}, volume = {69}, year = {2015}, } @article{9931, abstract = {Gene duplication is important in evolution, because it provides new raw material for evolutionary adaptations. Several existing hypotheses about the causes of duplicate retention and diversification differ in their emphasis on gene dosage, subfunctionalization, and neofunctionalization. Little experimental data exist on the relative importance of gene expression changes and changes in coding regions for the evolution of duplicate genes. Furthermore, we do not know how strongly the environment could affect this importance. To address these questions, we performed evolution experiments with the TEM-1 beta lactamase gene in Escherichia coli to study the initial stages of duplicate gene evolution in the laboratory. We mimicked tandem duplication by inserting two copies of the TEM-1 gene on the same plasmid. We then subjected these copies to repeated cycles of mutagenesis and selection in various environments that contained antibiotics in different combinations and concentrations. Our experiments showed that gene dosage is the most important factor in the initial stages of duplicate gene evolution, and overshadows the importance of point mutations in the coding region.}, author = {Dhar, Riddhiman and Bergmiller, Tobias and Wagner, Andreas}, issn = {1558-5646}, journal = {Evolution}, number = {6}, pages = {1775--1791}, publisher = {Wiley}, title = {{Increased gene dosage plays a predominant role in the initial stages of evolution of duplicate TEM-1 beta lactamase genes}}, doi = {10.1111/evo.12373}, volume = {68}, year = {2014}, } @article{4245, abstract = {Sex allocation theory has proved extremely successful at predicting when individuals should adjust the sex of their offspring in response to environmental conditions. However, we know rather little about the underlying genetics of sex ratio or how genetic architecture might constrain adaptive sex-ratio behavior. We examined how mutation influenced genetic variation in the sex ratios produced by the parasitoid wasp Nasonia vitripennis. In a mutation accumulation experiment, we determined the mutability of sex ratio, and compared this with the amount of genetic variation observed in natural populations. We found that the mutability (h2m) ranges from 0.001 to 0.002, similar to estimates for life-history traits in other organisms. These estimates suggest one mutation every 5–60 generations, which shift the sex ratio by approximately 0.01 (proportion males). In this and other studies, the genetic variation in N. vitripennis sex ratio ranged from 0.02 to 0.17 (broad-sense heritability, H2). If sex ratio is maintained by mutation–selection balance, a higher genetic variance would be expected given our mutational parameters. Instead, the observed genetic variance perhaps suggests additional selection against sex-ratio mutations with deleterious effects on other fitness traits as well as sex ratio (i.e., pleiotropy), as has been argued to be the case more generally.}, author = {Pannebakker, Bart and Halligan, Daniel and Reynolds, K Tracy and Ballantyne, Gavin and Shuker, David and Barton, Nicholas H and West, Stuart}, issn = {1558-5646}, journal = {Evolution; International Journal of Organic Evolution}, number = {8}, pages = {1921 -- 1935}, publisher = {Oxford Academic}, title = {{Effects of spontaneous mutation accumulation on sex ratio traits}}, doi = {10.1111/j.1558-5646.2008.00434.x}, volume = {62}, year = {2008}, } @article{4249, abstract = {We examined causes of speciation in asexual populations in both sympatry and parapatry, providing an alternative explanation for the speciation patterns reported by Dieckmann and Doebeli (1999) and Doebeli and Dieckmann (2003). Both in sympatry and parapatry, they find that speciation occurs relatively easily. We reveal that in the sympatric clonal model, the equilibrium distribution is continuous and the disruptive selection driving evolution of discrete clusters is only transient. Hence, if discrete phenotypes are to remain stable in the sympatric sexual model, there should be some source of nontransient disruptive selection that will drive evolution of assortment. We analyze sexually reproducing populations using the Bulmer’s infinitesimal model and show that cost-free assortment alone leads to speciation and disruptive selection only arises when the optimal distribution cannot be matched—in this example, because the phenotypic range is limited. In addition, Doebeli and Dieckmann’s analyses assumed a high genetic variance and a high mutation rate. Thus, these theoretical models do not support the conclusion that sympatric speciation is a likely outcome of competition for resources. In their parapatric model (Doebeli and Dieckmann 2003), clustering into distinct phenotypes is driven by edge effects, rather than by frequency-dependent competition.}, author = {Polechova, Jitka and Barton, Nicholas H}, issn = {1558-5646}, journal = {Evolution; International Journal of Organic Evolution}, number = {6}, pages = {1194 -- 1210}, publisher = {Wiley-Blackwell}, title = {{Speciation through competition: A critical review}}, doi = {10.1111/j.0014-3820.2005.tb01771.x}, volume = {59}, year = {2005}, }