@article{12166, abstract = {Kerstin Johannesson is a marine ecologist and evolutionary biologist based at the Tjärnö Marine Laboratory of the University of Gothenburg, which is situated in the beautiful Kosterhavet National Park on the Swedish west coast. Her work, using marine periwinkles (especially Littorina saxatilis and L. fabalis) as main model systems, has made a remarkable contribution to marine evolutionary biology and our understanding of local adaptation and its genetic underpinnings.}, author = {Westram, Anja M and Butlin, Roger}, issn = {1365-294X}, journal = {Molecular Ecology}, keywords = {Genetics, Ecology, Evolution, Behavior and Systematics}, number = {1}, pages = {26--29}, publisher = {Wiley}, title = {{Professor Kerstin Johannesson–winner of the 2022 Molecular Ecology Prize}}, doi = {10.1111/mec.16779}, volume = {32}, 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{12264, abstract = {Reproductive isolation (RI) is a core concept in evolutionary biology. It has been the central focus of speciation research since the modern synthesis and is the basis by which biological species are defined. Despite this, the term is used in seemingly different ways, and attempts to quantify RI have used very different approaches. After showing that the field lacks a clear definition of the term, we attempt to clarify key issues, including what RI is, how it can be quantified in principle, and how it can be measured in practice. Following other definitions with a genetic focus, we propose that RI is a quantitative measure of the effect that genetic differences between populations have on gene flow. Specifically, RI compares the flow of neutral alleles in the presence of these genetic differences to the flow without any such differences. RI is thus greater than zero when genetic differences between populations reduce the flow of neutral alleles between populations. We show how RI can be quantified in a range of scenarios. A key conclusion is that RI depends strongly on circumstances—including the spatial, temporal and genomic context—making it difficult to compare across systems. After reviewing methods for estimating RI from data, we conclude that it is difficult to measure in practice. We discuss our findings in light of the goals of speciation research and encourage the use of methods for estimating RI that integrate organismal and genetic approaches.}, author = {Westram, Anja M and Stankowski, Sean and Surendranadh, Parvathy and Barton, Nicholas H}, issn = {1420-9101}, journal = {Journal of Evolutionary Biology}, keywords = {Ecology, Evolution, Behavior and Systematics}, number = {9}, pages = {1143--1164}, publisher = {Wiley}, title = {{What is reproductive isolation?}}, doi = {10.1111/jeb.14005}, volume = {35}, year = {2022}, } @article{12265, author = {Westram, Anja M and Stankowski, Sean and Surendranadh, Parvathy and Barton, Nicholas H}, issn = {1420-9101}, journal = {Journal of Evolutionary Biology}, keywords = {Ecology, Evolution, Behavior and Systematics}, number = {9}, pages = {1200--1205}, publisher = {Wiley}, title = {{Reproductive isolation, speciation, and the value of disagreement: A reply to the commentaries on ‘What is reproductive isolation?’}}, doi = {10.1111/jeb.14082}, volume = {35}, year = {2022}, } @article{8708, abstract = {The Mytilus complex of marine mussel species forms a mosaic of hybrid zones, found across temperate regions of the globe. This allows us to study ‘replicated’ instances of secondary contact between closely related species. Previous work on this complex has shown that local introgression is both widespread and highly heterogeneous, and has identified SNPs that are outliers of differentiation between lineages. Here, we developed an ancestry‐informative panel of such SNPs. We then compared their frequencies in newly sampled populations, including samples from within the hybrid zones, and parental populations at different distances from the contact. Results show that close to the hybrid zones, some outlier loci are near to fixation for the heterospecific allele, suggesting enhanced local introgression, or the local sweep of a shared ancestral allele. Conversely, genomic cline analyses, treating local parental populations as the reference, reveal a globally high concordance among loci, albeit with a few signals of asymmetric introgression. Enhanced local introgression at specific loci is consistent with the early transfer of adaptive variants after contact, possibly including asymmetric bi‐stable variants (Dobzhansky‐Muller incompatibilities), or haplotypes loaded with fewer deleterious mutations. Having escaped one barrier, however, these variants can be trapped or delayed at the next barrier, confining the introgression locally. These results shed light on the decay of species barriers during phases of contact.}, author = {Simon, Alexis and Fraisse, Christelle and El Ayari, Tahani and Liautard‐Haag, Cathy and Strelkov, Petr and Welch, John J and Bierne, Nicolas}, issn = {14209101}, journal = {Journal of Evolutionary Biology}, number = {1}, pages = {208--223}, publisher = {Wiley}, title = {{How do species barriers decay? Concordance and local introgression in mosaic hybrid zones of mussels}}, doi = {10.1111/jeb.13709}, volume = {34}, year = {2021}, } @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{8928, abstract = {Domestication is a human‐induced selection process that imprints the genomes of domesticated populations over a short evolutionary time scale and that occurs in a given demographic context. Reconstructing historical gene flow, effective population size changes and their timing is therefore of fundamental interest to understand how plant demography and human selection jointly shape genomic divergence during domestication. Yet, the comparison under a single statistical framework of independent domestication histories across different crop species has been little evaluated so far. Thus, it is unclear whether domestication leads to convergent demographic changes that similarly affect crop genomes. To address this question, we used existing and new transcriptome data on three crop species of Solanaceae (eggplant, pepper and tomato), together with their close wild relatives. We fitted twelve demographic models of increasing complexity on the unfolded joint allele frequency spectrum for each wild/crop pair, and we found evidence for both shared and species‐specific demographic processes between species. A convergent history of domestication with gene flow was inferred for all three species, along with evidence of strong reduction in the effective population size during the cultivation stage of tomato and pepper. The absence of any reduction in size of the crop in eggplant stands out from the classical view of the domestication process; as does the existence of a “protracted period” of management before cultivation. Our results also suggest divergent management strategies of modern cultivars among species as their current demography substantially differs. Finally, the timing of domestication is species‐specific and supported by the few historical records available.}, author = {Arnoux, Stéphanie and Fraisse, Christelle and Sauvage, Christopher}, issn = {14209101}, journal = {Journal of Evolutionary Biology}, number = {2}, pages = {270--283}, publisher = {Wiley}, title = {{Genomic inference of complex domestication histories in three Solanaceae species}}, doi = {10.1111/jeb.13723}, volume = {34}, year = {2021}, } @inbook{14984, abstract = {Hybrid zones are narrow geographic regions where different populations, races or interbreeding species meet and mate, producing mixed ‘hybrid’ offspring. They are relatively common and can be found in a diverse range of organisms and environments. The study of hybrid zones has played an important role in our understanding of the origin of species, with hybrid zones having been described as ‘natural laboratories’. This is because they allow us to study,in situ, the conditions and evolutionary forces that enable divergent taxa to remain distinct despite some ongoing gene exchange between them.}, author = {Stankowski, Sean and Shipilina, Daria and Westram, Anja M}, booktitle = {Encyclopedia of Life Sciences}, isbn = {9780470016176}, publisher = {Wiley}, title = {{Hybrid Zones}}, doi = {10.1002/9780470015902.a0029355}, volume = {2}, year = {2021}, } @misc{13062, abstract = {This paper analyzes 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}, publisher = {Dryad}, title = {{Supplementary code for: Polygenic local adaptation in metapopulations: A stochastic eco-evolutionary model}}, doi = {10.5061/DRYAD.8GTHT76P1}, year = {2021}, } @article{9100, abstract = {Marine environments are inhabited by a broad representation of the tree of life, yet our understanding of speciation in marine ecosystems is extremely limited compared with terrestrial and freshwater environments. Developing a more comprehensive picture of speciation in marine environments requires that we 'dive under the surface' by studying a wider range of taxa and ecosystems is necessary for a more comprehensive picture of speciation. Although studying marine evolutionary processes is often challenging, recent technological advances in different fields, from maritime engineering to genomics, are making it increasingly possible to study speciation of marine life forms across diverse ecosystems and taxa. Motivated by recent research in the field, including the 14 contributions in this issue, we highlight and discuss six axes of research that we think will deepen our understanding of speciation in the marine realm: (a) study a broader range of marine environments and organisms; (b) identify the reproductive barriers driving speciation between marine taxa; (c) understand the role of different genomic architectures underlying reproductive isolation; (d) infer the evolutionary history of divergence using model‐based approaches; (e) study patterns of hybridization and introgression between marine taxa; and (f) implement highly interdisciplinary, collaborative research programmes. In outlining these goals, we hope to inspire researchers to continue filling this critical knowledge gap surrounding the origins of marine biodiversity.}, author = {Faria, Rui and Johannesson, Kerstin and Stankowski, Sean}, issn = {14209101}, journal = {Journal of Evolutionary Biology}, number = {1}, pages = {4--15}, publisher = {Wiley}, title = {{Speciation in marine environments: Diving under the surface}}, doi = {10.1111/jeb.13756}, volume = {34}, year = {2021}, } @article{9119, abstract = {We present DILS, a deployable statistical analysis platform for conducting demographic inferences with linked selection from population genomic data using an Approximate Bayesian Computation framework. DILS takes as input single‐population or two‐population data sets (multilocus fasta sequences) and performs three types of analyses in a hierarchical manner, identifying: (a) the best demographic model to study the importance of gene flow and population size change on the genetic patterns of polymorphism and divergence, (b) the best genomic model to determine whether the effective size Ne and migration rate N, m are heterogeneously distributed along the genome (implying linked selection) and (c) loci in genomic regions most associated with barriers to gene flow. Also available via a Web interface, an objective of DILS is to facilitate collaborative research in speciation genomics. Here, we show the performance and limitations of DILS by using simulations and finally apply the method to published data on a divergence continuum composed by 28 pairs of Mytilus mussel populations/species.}, author = {Fraisse, Christelle and Popovic, Iva and Mazoyer, Clément and Spataro, Bruno and Delmotte, Stéphane and Romiguier, Jonathan and Loire, Étienne and Simon, Alexis and Galtier, Nicolas and Duret, Laurent and Bierne, Nicolas and Vekemans, Xavier and Roux, Camille}, issn = {17550998}, journal = {Molecular Ecology Resources}, pages = {2629--2644}, publisher = {Wiley}, title = {{DILS: Demographic inferences with linked selection by using ABC}}, doi = {10.1111/1755-0998.13323}, volume = {21}, year = {2021}, } @article{9168, abstract = {Interspecific crossing experiments have shown that sex chromosomes play a major role in reproductive isolation between many pairs of species. However, their ability to act as reproductive barriers, which hamper interspecific genetic exchange, has rarely been evaluated quantitatively compared to Autosomes. This genome-wide limitation of gene flow is essential for understanding the complete separation of species, and thus speciation. Here, we develop a mainland-island model of secondary contact between hybridizing species of an XY (or ZW) sexual system. We obtain theoretical predictions for the frequency of introgressed alleles, and the strength of the barrier to neutral gene flow for the two types of chromosomes carrying multiple interspecific barrier loci. Theoretical predictions are obtained for scenarios where introgressed alleles are rare. We show that the same analytical expressions apply for sex chromosomes and autosomes, but with different sex-averaged effective parameters. The specific features of sex chromosomes (hemizygosity and absence of recombination in the heterogametic sex) lead to reduced levels of introgression on the X (or Z) compared to autosomes. This effect can be enhanced by certain types of sex-biased forces, but it remains overall small (except when alleles causing incompatibilities are recessive). We discuss these predictions in the light of empirical data comprising model-based tests of introgression and cline surveys in various biological systems.}, author = {Fraisse, Christelle and Sachdeva, Himani}, issn = {1943-2631}, journal = {Genetics}, number = {2}, publisher = {Genetics Society of America}, title = {{The rates of introgression and barriers to genetic exchange between hybridizing species: Sex chromosomes vs autosomes}}, doi = {10.1093/genetics/iyaa025}, volume = {217}, year = {2021}, } @misc{9192, abstract = {Here are the research data underlying the publication " Effects of fine-scale population structure on inbreeding in a long-term study of snapdragons (Antirrhinum majus)." Further information are summed up in the README document.}, author = {Surendranadh, Parvathy and Arathoon, Louise S and Baskett, Carina and Field, David and Pickup, Melinda and Barton, Nicholas H}, publisher = {Institute of Science and Technology Austria}, title = {{Effects of fine-scale population structure on the distribution of heterozygosity in a long-term study of Antirrhinum majus}}, doi = {10.15479/AT:ISTA:9192}, 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{9375, abstract = {Genetic variation segregates as linked sets of variants, or haplotypes. Haplotypes and linkage are central to genetics and underpin virtually all genetic and selection analysis. And yet, genomic data often lack haplotype information, due to constraints in sequencing technologies. Here we present “haplotagging”, a simple, low-cost linked-read sequencing technique that allows sequencing of hundreds of individuals while retaining linkage information. We apply haplotagging to construct megabase-size haplotypes for over 600 individual butterflies (Heliconius erato and H. melpomene), which form overlapping hybrid zones across an elevational gradient in Ecuador. Haplotagging identifies loci controlling distinctive high- and lowland wing color patterns. Divergent haplotypes are found at the same major loci in both species, while chromosome rearrangements show no parallelism. Remarkably, in both species the geographic clines for the major wing pattern loci are displaced by 18 km, leading to the rise of a novel hybrid morph in the centre of the hybrid zone. We propose that shared warning signalling (Müllerian mimicry) may couple the cline shifts seen in both species, and facilitate the parallel co-emergence of a novel hybrid morph in both co-mimetic species. Our results show the power of efficient haplotyping methods when combined with large-scale sequencing data from natural populations.}, author = {Meier, Joana I. and Salazar, Patricio A. and Kučka, Marek and Davies, Robert William and Dréau, Andreea and Aldás, Ismael and Power, Olivia Box and Nadeau, Nicola J. and Bridle, Jon R. and Rolian, Campbell and Barton, Nicholas H and McMillan, W. Owen and Jiggins, Chris D. and Chan, Yingguang Frank}, issn = {0027-8424}, journal = {PNAS}, number = {25}, publisher = {Proceedings of the National Academy of Sciences}, title = {{Haplotype tagging reveals parallel formation of hybrid races in two butterfly species}}, doi = {10.1073/pnas.2015005118}, volume = {118}, 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{9392, abstract = {Humans conceptualize the diversity of life by classifying individuals into types we call ‘species’1. The species we recognize influence political and financial decisions and guide our understanding of how units of diversity evolve and interact. Although the idea of species may seem intuitive, a debate about the best way to define them has raged even before Darwin2. So much energy has been devoted to the so-called ‘species problem’ that no amount of discourse will ever likely solve it2,3. Dozens of species concepts are currently recognized3, but we lack a concrete understanding of how much researchers actually disagree and the factors that cause them to think differently1,2. To address this, we used a survey to quantify the species problem for the first time. The results indicate that the disagreement is extensive: two randomly chosen respondents will most likely disagree on the nature of species. The probability of disagreement is not predicted by researcher experience or broad study system, but tended to be lower among researchers with similar focus, training and who study the same organism. Should we see this diversity of perspectives as a problem? We argue that we should not.}, author = {Stankowski, Sean and Ravinet, Mark}, issn = {18790445}, journal = {Current Biology}, number = {9}, pages = {R428--R429}, publisher = {Cell Press}, title = {{Quantifying the use of species concepts}}, doi = {10.1016/j.cub.2021.03.060}, volume = {31}, year = {2021}, } @article{9394, abstract = {Chromosomal inversions have long been recognized for their role in local adaptation. By suppressing recombination in heterozygous individuals, they can maintain coadapted gene complexes and protect them from homogenizing effects of gene flow. However, to fully understand their importance for local adaptation we need to know their influence on phenotypes under divergent selection. For this, the marine snail Littorina saxatilis provides an ideal study system. Divergent ecotypes adapted to wave action and crab predation occur in close proximity on intertidal shores with gene flow between them. Here, we used F2 individuals obtained from crosses between the ecotypes to test for associations between genomic regions and traits distinguishing the Crab‐/Wave‐adapted ecotypes including size, shape, shell thickness, and behavior. We show that most of these traits are influenced by two previously detected inversion regions that are divergent between ecotypes. We thus gain a better understanding of one important underlying mechanism responsible for the rapid and repeated formation of ecotypes: divergent selection acting on inversions. We also found that some inversions contributed to more than one trait suggesting that they may contain several loci involved in adaptation, consistent with the hypothesis that suppression of recombination within inversions facilitates differentiation in the presence of gene flow.}, author = {Koch, Eva L. and Morales, Hernán E. and Larsson, Jenny and Westram, Anja M and Faria, Rui and Lemmon, Alan R. and Lemmon, E. Moriarty and Johannesson, Kerstin and Butlin, Roger K.}, issn = {2056-3744}, journal = {Evolution Letters}, number = {3}, pages = {196--213}, publisher = {Wiley}, title = {{Genetic variation for adaptive traits is associated with polymorphic inversions in Littorina saxatilis}}, doi = {10.1002/evl3.227}, volume = {5}, year = {2021}, }