@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{8112, author = {Barton, Nicholas H}, issn = {1471-2970}, journal = {Philosophical Transactions of the Royal Society. Series B: Biological Sciences}, number = {1806}, publisher = {The Royal Society}, title = {{On the completion of speciation}}, doi = {10.1098/rstb.2019.0530}, volume = {375}, year = {2020}, } @article{8167, abstract = {The evolution of strong reproductive isolation (RI) is fundamental to the origins and maintenance of biological diversity, especially in situations where geographical distributions of taxa broadly overlap. But what is the history behind strong barriers currently acting in sympatry? Using whole-genome sequencing and single nucleotide polymorphism genotyping, we inferred (i) the evolutionary relationships, (ii) the strength of RI, and (iii) the demographic history of divergence between two broadly sympatric taxa of intertidal snail. Despite being cryptic, based on external morphology, Littorina arcana and Littorina saxatilis differ in their mode of female reproduction (egg-laying versus brooding), which may generate a strong post-zygotic barrier. We show that egg-laying and brooding snails are closely related, but genetically distinct. Genotyping of 3092 snails from three locations failed to recover any recent hybrid or backcrossed individuals, confirming that RI is strong. There was, however, evidence for a very low level of asymmetrical introgression, suggesting that isolation remains incomplete. The presence of strong, asymmetrical RI was further supported by demographic analysis of these populations. Although the taxa are currently broadly sympatric, demographic modelling suggests that they initially diverged during a short period of geographical separation involving very low gene flow. Our study suggests that some geographical separation may kick-start the evolution of strong RI, facilitating subsequent coexistence of taxa in sympatry. The strength of RI needed to achieve sympatry and the subsequent effect of sympatry on RI remain open questions.}, author = {Stankowski, Sean and Westram, Anja M and Zagrodzka, Zuzanna B. and Eyres, Isobel and Broquet, Thomas and Johannesson, Kerstin and Butlin, Roger K.}, issn = {1471-2970}, journal = {Philosophical Transactions of the Royal Society. Series B: Biological Sciences}, number = {1806}, publisher = {The Royal Society}, title = {{The evolution of strong reproductive isolation between sympatric intertidal snails}}, doi = {10.1098/rstb.2019.0545}, volume = {375}, year = {2020}, } @article{8168, abstract = {Speciation, that is, the evolution of reproductive barriers eventually leading to complete isolation, is a crucial process generating biodiversity. Recent work has contributed much to our understanding of how reproductive barriers begin to evolve, and how they are maintained in the face of gene flow. However, little is known about the transition from partial to strong reproductive isolation (RI) and the completion of speciation. We argue that the evolution of strong RI is likely to involve different processes, or new interactions among processes, compared with the evolution of the first reproductive barriers. Transition to strong RI may be brought about by changing external conditions, for example, following secondary contact. However, the increasing levels of RI themselves create opportunities for new barriers to evolve and, and interaction or coupling among barriers. These changing processes may depend on genomic architecture and leave detectable signals in the genome. We outline outstanding questions and suggest more theoretical and empirical work, considering both patterns and processes associated with strong RI, is needed to understand how speciation is completed.}, author = {Kulmuni, Jonna and Butlin, Roger K. and Lucek, Kay and Savolainen, Vincent and Westram, Anja M}, issn = {1471-2970}, journal = {Philosophical Transactions of the Royal Society. Series B: Biological sciences}, number = {1806}, publisher = {The Royal Society}, title = {{Towards the completion of speciation: The evolution of reproductive isolation beyond the first barriers}}, doi = {10.1098/rstb.2019.0528}, volume = {375}, year = {2020}, } @misc{8254, abstract = {Here are the research data underlying the publication "Estimating inbreeding and its effects in a long-term study of snapdragons (Antirrhinum majus)". Further information are summed up in the README document. The files for this record have been updated and are now found in the linked DOI https://doi.org/10.15479/AT:ISTA:9192.}, author = {Arathoon, Louise S}, publisher = {Institute of Science and Technology Austria}, title = {{Estimating inbreeding and its effects in a long-term study of snapdragons (Antirrhinum majus)}}, doi = {10.15479/AT:ISTA:8254}, year = {2020}, } @misc{8809, 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 Rafajlovic, Marina and Westram, Anja M and Johannesson, Kerstin and Butlin, Roger}, publisher = {Dryad}, title = {{Data from: Assortative mating, sexual selection and their consequences for gene flow in Littorina}}, doi = {10.5061/dryad.qrfj6q5cn}, year = {2020}, } @misc{9798, abstract = {Fitness interactions between mutations can influence a population’s evolution in many different ways. While epistatic effects are difficult to measure precisely, important information is captured by the mean and variance of log fitnesses for individuals carrying different numbers of mutations. We derive predictions for these quantities from a class of simple fitness landscapes, based on models of optimizing selection on quantitative traits. We also explore extensions to the models, including modular pleiotropy, variable effect sizes, mutational bias and maladaptation of the wild type. We illustrate our approach by reanalysing a large dataset of mutant effects in a yeast snoRNA. Though characterized by some large epistatic effects, these data give a good overall fit to the non-epistatic null model, suggesting that epistasis might have limited influence on the evolutionary dynamics in this system. We also show how the amount of epistasis depends on both the underlying fitness landscape and the distribution of mutations, and so is expected to vary in consistent ways between new mutations, standing variation and fixed mutations.}, author = {Fraisse, Christelle and Welch, John J.}, publisher = {Royal Society of London}, title = {{Simulation code for Fig S2 from the distribution of epistasis on simple fitness landscapes}}, doi = {10.6084/m9.figshare.7957472.v1}, year = {2020}, } @misc{9799, abstract = {Fitness interactions between mutations can influence a population’s evolution in many different ways. While epistatic effects are difficult to measure precisely, important information is captured by the mean and variance of log fitnesses for individuals carrying different numbers of mutations. We derive predictions for these quantities from a class of simple fitness landscapes, based on models of optimizing selection on quantitative traits. We also explore extensions to the models, including modular pleiotropy, variable effect sizes, mutational bias and maladaptation of the wild type. We illustrate our approach by reanalysing a large dataset of mutant effects in a yeast snoRNA. Though characterized by some large epistatic effects, these data give a good overall fit to the non-epistatic null model, suggesting that epistasis might have limited influence on the evolutionary dynamics in this system. We also show how the amount of epistasis depends on both the underlying fitness landscape and the distribution of mutations, and so is expected to vary in consistent ways between new mutations, standing variation and fixed mutations.}, author = {Fraisse, Christelle and Welch, John J.}, publisher = {Royal Society of London}, title = {{Simulation code for Fig S1 from the distribution of epistasis on simple fitness landscapes}}, doi = {10.6084/m9.figshare.7957469.v1}, year = {2020}, } @article{7205, abstract = {Genetic incompatibilities contribute to reproductive isolation between many diverging populations, but it is still unclear to what extent they play a role if divergence happens with gene flow. In contact zones between the "Crab" and "Wave" ecotypes of the snail Littorina saxatilis, divergent selection forms strong barriers to gene flow, while the role of post‐zygotic barriers due to selection against hybrids remains unclear. High embryo abortion rates in this species could indicate the presence of such barriers. Post‐zygotic barriers might include genetic incompatibilities (e.g. Dobzhansky–Muller incompatibilities) but also maladaptation, both expected to be most pronounced in contact zones. In addition, embryo abortion might reflect physiological stress on females and embryos independent of any genetic stress. We examined all embryos of >500 females sampled outside and inside contact zones of three populations in Sweden. Females' clutch size ranged from 0 to 1,011 embryos (mean 130 ± 123), and abortion rates varied between 0% and 100% (mean 12%). We described female genotypes by using a hybrid index based on hundreds of SNPs differentiated between ecotypes with which we characterized female genotypes. We also calculated female SNP heterozygosity and inversion karyotype. Clutch size did not vary with female hybrid index, and abortion rates were only weakly related to hybrid index in two sites but not at all in a third site. No additional variation in abortion rate was explained by female SNP heterozygosity, but increased female inversion heterozygosity added slightly to increased abortion. Our results show only weak and probably biologically insignificant post‐zygotic barriers contributing to ecotype divergence, and the high and variable abortion rates were marginally, if at all, explained by hybrid index of females.}, author = {Johannesson, Kerstin and Zagrodzka, Zuzanna and Faria, Rui and Westram, Anja M and Butlin, Roger K.}, issn = {1420-9101}, journal = {Journal of Evolutionary Biology}, number = {3}, pages = {342--351}, publisher = {Wiley}, title = {{Is embryo abortion a post-zygotic barrier to gene flow between Littorina ecotypes?}}, doi = {10.1111/jeb.13570}, volume = {33}, year = {2020}, } @article{7236, abstract = {The biotic interactions hypothesis posits that biotic interactions are more important drivers of adaptation closer to the equator, evidenced by “stronger” contemporary interactions (e.g. greater interaction rates) and/or patterns of trait evolution consistent with a history of stronger interactions. Support for the hypothesis is mixed, but few studies span tropical and temperate regions while experimentally controlling for evolutionary history. Here, we integrate field observations and common garden experiments to quantify the relative importance of pollination and herbivory in a pair of tropical‐temperate congeneric perennial herbs. Phytolacca rivinoides and P. americana are pioneer species native to the Neotropics and the eastern USA, respectively. We compared plant‐pollinator and plant‐herbivore interactions between three tropical populations of P. rivinoides from Costa Rica and three temperate populations of P. americana from its northern range edge in Michigan and Ohio. For some metrics of interaction importance, we also included three subtropical populations of P. americana from its southern range edge in Florida. This approach confounds species and region but allows us, uniquely, to measure complementary proxies of interaction importance across a tropical‐temperate range in one system. To test the prediction that lower‐latitude plants are more reliant on insect pollinators, we quantified floral display and reward, insect visitation rates, and self‐pollination ability (autogamy). To test the prediction that lower‐latitude plants experience more herbivore pressure, we quantified herbivory rates, herbivore abundance, and leaf palatability. We found evidence supporting the biotic interactions hypothesis for most comparisons between P. rivinoides and north‐temperate P. americana (floral display, insect visitation, autogamy, herbivory, herbivore abundance, and young‐leaf palatability). Results for subtropical P. americana populations, however, were typically not intermediate between P. rivinoides and north‐temperate P. americana, as would be predicted by a linear latitudinal gradient in interaction importance. Subtropical young‐leaf palatability was intermediate, but subtropical mature leaves were the least palatable, and pollination‐related traits did not differ between temperate and subtropical regions. These nonlinear patterns of interaction importance suggest future work to relate interaction importance to climatic or biotic thresholds. In sum, we found that the biotic interactions hypothesis was more consistently supported at the larger spatial scale of our study.}, author = {Baskett, Carina and Schroeder, Lucy and Weber, Marjorie G. and Schemske, Douglas W.}, issn = {1557-7015}, journal = {Ecological Monographs}, number = {1}, publisher = {Wiley}, title = {{Multiple metrics of latitudinal patterns in insect pollination and herbivory for a tropical‐temperate congener pair}}, doi = {10.1002/ecm.1397}, volume = {90}, year = {2020}, } @article{7651, abstract = {The growth of snail shells can be described by simple mathematical rules. Variation in a few parameters can explain much of the diversity of shell shapes seen in nature. However, empirical studies of gastropod shell shape variation typically use geometric morphometric approaches, which do not capture this growth pattern. We have developed a way to infer a set of developmentally descriptive shape parameters based on three-dimensional logarithmic helicospiral growth and using landmarks from two-dimensional shell images as input. We demonstrate the utility of this approach, and compare it to the geometric morphometric approach, using a large set of Littorina saxatilis shells in which locally adapted populations differ in shape. Our method can be modified easily to make it applicable to a wide range of shell forms, which would allow for investigations of the similarities and differences between and within many different species of gastropods.}, author = {Larsson, J. and Westram, Anja M and Bengmark, S. and Lundh, T. and Butlin, R. K.}, issn = {1742-5662}, journal = {Journal of The Royal Society Interface}, number = {163}, publisher = {The Royal Society}, title = {{A developmentally descriptive method for quantifying shape in gastropod shells}}, doi = {10.1098/rsif.2019.0721}, volume = {17}, year = {2020}, } @article{8169, abstract = {Many recent studies have addressed the mechanisms operating during the early stages of speciation, but surprisingly few studies have tested theoretical predictions on the evolution of strong reproductive isolation (RI). To help address this gap, we first undertook a quantitative review of the hybrid zone literature for flowering plants in relation to reproductive barriers. Then, using Populus as an exemplary model group, we analysed genome-wide variation for phylogenetic tree topologies in both early- and late-stage speciation taxa to determine how these patterns may be related to the genomic architecture of RI. Our plant literature survey revealed variation in barrier complexity and an association between barrier number and introgressive gene flow. Focusing on Populus, our genome-wide analysis of tree topologies in speciating poplar taxa points to unusually complex genomic architectures of RI, consistent with earlier genome-wide association studies. These architectures appear to facilitate the ‘escape’ of introgressed genome segments from polygenic barriers even with strong RI, thus affecting their relationships with recombination rates. Placed within the context of the broader literature, our data illustrate how phylogenomic approaches hold great promise for addressing the evolution and temporary breakdown of RI during late stages of speciation.}, author = {Shang, Huiying and Hess, Jaqueline and Pickup, Melinda and Field, David and Ingvarsson, Pär K. and Liu, Jianquan and Lexer, Christian}, issn = {1471-2970}, journal = {Philosophical Transactions of the Royal Society. Series B: Biological Sciences}, number = {1806}, publisher = {The Royal Society}, title = {{Evolution of strong reproductive isolation in plants: Broad-scale patterns and lessons from a perennial model group}}, doi = {10.1098/rstb.2019.0544}, volume = {375}, year = {2020}, } @phdthesis{8574, abstract = {This thesis concerns itself with the interactions of evolutionary and ecological forces and the consequences on genetic diversity and the ultimate survival of populations. It is important to understand what signals processes leave on the genome and what we can infer from such data, which is usually abundant but noisy. Furthermore, understanding how and when populations adapt or go extinct is important for practical purposes, such as the genetic management of populations, as well as for theoretical questions, since local adaptation can be the first step toward speciation. In Chapter 2, we introduce the method of maximum entropy to approximate the demographic changes of a population in a simple setting, namely the logistic growth model with immigration. We show that this method is not only a powerful tool in physics but can be gainfully applied in an ecological framework. We investigate how well it approximates the real behavior of the system, and find that is does so, even in unexpected situations. Finally, we illustrate how it can model changing environments. In Chapter 3, we analyze the co-evolution of allele frequencies and population sizes in an infinite island model. We give conditions under which polygenic adaptation to a rare habitat is possible. The model we use is based on the diffusion approximation, considers eco-evolutionary feedback mechanisms (hard selection), and treats both drift and environmental fluctuations explicitly. We also look at limiting scenarios, for which we derive analytical expressions. In Chapter 4, we present a coalescent based simulation tool to obtain patterns of diversity in a spatially explicit subdivided population, in which the demographic history of each subpopulation can be specified. We compare the results to existing predictions, and explore the relative importance of time and space under a variety of spatial arrangements and demographic histories, such as expansion and extinction. In the last chapter, we give a brief outlook to further research. }, author = {Szep, Eniko}, issn = {2663-337X}, pages = {158}, publisher = {Institute of Science and Technology Austria}, title = {{Local adaptation in metapopulations}}, doi = {10.15479/AT:ISTA:8574}, year = {2020}, } @inbook{9123, abstract = {Inversions are chromosomal rearrangements where the order of genes is reversed. Inversions originate by mutation and can be under positive, negative or balancing selection. Selective effects result from potential disruptive effects on meiosis, gene disruption at inversion breakpoints and, importantly, the effects of inversions as modifiers of recombination rate: Recombination is strongly reduced in individuals heterozygous for an inversion, allowing for alleles at different loci to be inherited as a ‘block’. This may lead to a selective advantage whenever it is favourable to keep certain combinations of alleles associated, for example under local adaptation with gene flow. Inversions can cover a considerable part of a chromosome and contain numerous loci under different selection pressures, so that the resulting overall effects may be complex. Empirical data from various systems show that inversions may have a prominent role in local adaptation, speciation, parallel evolution, the maintenance of polymorphism and sex chromosome evolution.}, author = {Westram, Anja M and Faria, Rui and Butlin, Roger and Johannesson, Kerstin}, booktitle = {eLS}, isbn = {9780470016176}, issn = {9780470015902}, publisher = {Wiley}, title = {{Inversions and Evolution}}, doi = {10.1002/9780470015902.a0029007}, year = {2020}, } @misc{13067, abstract = {Genetic incompatibilities contribute to reproductive isolation between many diverging populations, but it is still unclear to what extent they play a role if divergence happens with gene flow. In contact zones between the "Crab" and "Wave" ecotypes of the snail Littorina saxatilis divergent selection forms strong barriers to gene flow, while the role of postzygotic barriers due to selection against hybrids remains unclear. High embryo abortion rates in this species could indicate the presence of such barriers. Postzygotic barriers might include genetic incompatibilities (e.g. Dobzhansky-Muller incompatibilities) but also maladaptation, both expected to be most pronounced in contact zones. In addition, embryo abortion might reflect physiological stress on females and embryos independent of any genetic stress. We examined all embryos of >500 females sampled outside and inside contact zones of three populations in Sweden. Females' clutch size ranged from 0 to 1011 embryos (mean 130±123) and abortion rates varied between 0 and100% (mean 12%). We described female genotypes by using a hybrid index based on hundreds of SNPs differentiated between ecotypes with which we characterised female genotypes. We also calculated female SNP heterozygosity and inversion karyotype. Clutch size did not vary with female hybrid index and abortion rates were only weakly related to hybrid index in two sites but not at all in a third site. No additional variation in abortion rate was explained by female SNP heterozygosity, but increased female inversion heterozygosity added slightly to increased abortion. Our results show only weak and probably biologically insignificant postzygotic barriers contributing to ecotype divergence and the high and variable abortion rates were marginally, if at all, explained by hybrid index of females.}, author = {Johannesson, Kerstin and Zagrodzka, Zuzanna and Faria, Rui and Westram, Anja M and Butlin, Roger}, publisher = {Dryad}, title = {{Data from: Is embryo abortion a postzygotic barrier to gene flow between Littorina ecotypes?}}, doi = {10.5061/DRYAD.TB2RBNZWK}, year = {2019}, } @inbook{8281, abstract = {We review the history of population genetics, starting with its origins a century ago from the synthesis between Mendel and Darwin's ideas, through to the recent development of sophisticated schemes of inference from sequence data, based on the coalescent. We explain the close relation between the coalescent and a diffusion process, which we illustrate by their application to understand spatial structure. We summarise the powerful methods available for analysis of multiple loci, when linkage equilibrium can be assumed, and then discuss approaches to the more challenging case, where associations between alleles require that we follow genotype, rather than allele, frequencies. Though we can hardly cover the whole of population genetics, we give an overview of the current state of the subject, and future challenges to it.}, author = {Barton, Nicholas H and Etheridge, Alison}, booktitle = {Handbook of statistical genomics}, editor = {Balding, David and Moltke, Ida and Marioni, John}, isbn = {9781119429142}, pages = {115--144}, publisher = {Wiley}, title = {{Mathematical models in population genetics}}, doi = {10.1002/9781119487845.ch4}, year = {2019}, } @misc{9801, author = {Merrill, Richard M. and Rastas, Pasi and Martin, Simon H. and Melo Hurtado, Maria C and Barker, Sarah and Davey, John and Mcmillan, W. Owen and Jiggins, Chris D.}, publisher = {Public Library of Science}, title = {{Raw behavioral data}}, doi = {10.1371/journal.pbio.2005902.s006}, year = {2019}, } @misc{9802, 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}, publisher = {Dryad}, title = {{Data from: Effect of partial selfing and polygenic selection on establishment in a new habitat}}, doi = {10.5061/dryad.8tp0900}, year = {2019}, } @misc{9804, abstract = {Evolutionary studies are often limited by missing data that are critical to understanding the history of selection. Selection experiments, which reproduce rapid evolution under controlled conditions, are excellent tools to study how genomes evolve under selection. Here we present a genomic dissection of the Longshanks selection experiment, in which mice were selectively bred over 20 generations for longer tibiae relative to body mass, resulting in 13% longer tibiae in two replicates. We synthesized evolutionary theory, genome sequences and molecular genetics to understand the selection response and found that it involved both polygenic adaptation and discrete loci of major effect, with the strongest loci tending to be selected in parallel between replicates. We show that selection may favor de-repression of bone growth through inactivating two limb enhancers of an inhibitor, Nkx3-2. Our integrative genomic analyses thus show that it is possible to connect individual base-pair changes to the overall selection response.}, author = {Castro, João Pl and Yancoskie, Michelle N. and Marchini, Marta and Belohlavy, Stefanie and Hiramatsu, Layla and Kučka, Marek and Beluch, William H. and Naumann, Ronald and Skuplik, Isabella and Cobb, John and Barton, Nicholas H and Rolian, Campbell and Chan, Yingguang Frank}, publisher = {Dryad}, title = {{Data from: An integrative genomic analysis of the Longshanks selection experiment for longer limbs in mice}}, doi = {10.5061/dryad.0q2h6tk}, year = {2019}, } @misc{9805, abstract = {The spread of adaptive alleles is fundamental to evolution, and in theory, this process is well‐understood. However, only rarely can we follow this process—whether it originates from the spread of a new mutation, or by introgression from another population. In this issue of Molecular Ecology, Hanemaaijer et al. (2018) report on a 25‐year long study of the mosquitoes Anopheles gambiae (Figure 1) and Anopheles coluzzi in Mali, based on genotypes at 15 single‐nucleotide polymorphism (SNP). The species are usually reproductively isolated from each other, but in 2002 and 2006, bursts of hybridization were observed, when F1 hybrids became abundant. Alleles backcrossed from A. gambiae into A. coluzzi, but after the first event, these declined over the following years. In contrast, after 2006, an insecticide resistance allele that had established in A. gambiae spread into A. coluzzi, and rose to high frequency there, over 6 years (~75 generations). Whole genome sequences of 74 individuals showed that A. gambiae SNP from across the genome had become common in the A. coluzzi population, but that most of these were clustered in 34 genes around the resistance locus. A new set of SNP from 25 of these genes were assayed over time; over the 4 years since near‐fixation of the resistance allele; some remained common, whereas others declined. What do these patterns tell us about this introgression event?}, author = {Barton, Nicholas H}, publisher = {Dryad}, title = {{Data from: The consequences of an introgression event}}, doi = {10.5061/dryad.2kb6fh4}, year = {2019}, }