Molecular biology and evolution最新文献

{"title":"Temperature-sensitive cytoplasmic incompatibility across divergent Wolbachia partly reflects cifB transcription, not endosymbiont density.","authors":"Basabi Bagchi, Lore Van Vlaenderen, Tim Wheeler, Elena Provencal, William R Conner, Kyle McGuire, Brandon S Cooper, J Dylan Shropshire","doi":"10.1093/molbev/msag186","DOIUrl":"10.1093/molbev/msag186","url":null,"abstract":"<p><p>Maternally transmitted Wolbachia bacteria are common in insects, with many strains altering host reproduction through cytoplasmic incompatibility (CI). Cytoplasmic incompatibility kills embryos fertilized by Wolbachia-bearing males unless those embryos also carry Wolbachia, which favors females with Wolbachia and drives the endosymbiont to higher frequencies in host populations. Strong CI now underpins successful applications that rely on maintaining pathogen-blocking Wolbachia transinfections in vector populations to reduce arboviral disease transmission. Temperature modulates CI strength (the proportion of embryos killed), with consequences for Wolbachia prevalence in natural and transinfected populations. Yet the mechanisms regulating temperature-sensitive CI-strength variation are poorly understood. We quantified CI strength across eight divergent Drosophila-associated Wolbachia strains at four temperatures (18 to 26 °C), while characterizing development time, Wolbachia and Wovirus densities, and transcription of the CI-inducing gene cifB. Four of eight Wolbachia strains exhibited temperature-sensitive CI, three of which induced CI at multiple temperatures. Of these three, two expressed significantly more cifB at the temperature yielding stronger CI, whereas testes Wolbachia density did not predict CI strength. Notably, cifB-transcript levels were consistently decoupled from Wolbachia and Wovirus densities, suggesting that cifB transcription is not regulated solely by symbiont abundance. We also report temperature-sensitive rescue of CI, Wolbachia-associated developmental acceleration, and strain-specific Wovirus-Wolbachia covariance. Our findings reveal temperature as a pervasive modulator of Wolbachia-host interactions at multiple levels and extend evidence that cifB transcription partly predicts variable CI strength across strain identities, male ages, and now temperatures. Cytoplasmic incompatibility variation unaccounted for by cifB transcription points toward additional regulatory or posttranscriptional mechanisms that we discuss.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13455621/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148562619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plasticity-first evolution via CYP405 loss shaped chemical defenses in butterflies.","authors":"Erika C Pinheiro de Castro, Francesco Cicconardi, Ian A Warren, Nicol Rueda-M, Camilo Salazar, Søren Bak, Stephen H Montgomery, Chris D Jiggins","doi":"10.1093/molbev/msag197","DOIUrl":"10.1093/molbev/msag197","url":null,"abstract":"<p><p>Phenotypic plasticity allows a single genotype to maintain its fitness across different environments. This facilitates colonization of new niches but can be further refined or even lost as lineages diversify. The toxic Heliconiini butterflies have biochemical plasticity: they either sequester their cyanogenic glucosides (CGs) from their larval host plant or biosynthesize them when compounds for sequestration are not available. Here, we trace the evolution of CG biosynthesis in Heliconiini butterflies, a fundamental component of this biochemical plasticity. We first reconstructed the evolutionary history of biochemical plasticity in Heliconiini using chemical data from over 700 individuals, demonstrating that plasticity was ancestral in the tribe but subsequently lost in a few clades, such as the Sapho clade specialized in CG sequestration. In lepidopterans, CG biosynthesis has previously been characterized in the moth Zygaena filipendulae, as the genes CYP405A2, CYP332A3, and UGT33A1. Thus, we CRISPR-edited CYP405 in Heliconius erato and confirmed that CYP405-knockout caterpillars do not biosynthesize CGs. We identified the CYP405As and CYP332As in other lepidopterans and found that both genes were independently co-opted into CG biosynthesis in the Heliconiinae butterflies and Zygaena moths. While most lepidopterans have a CYP332A, CYP405A is mostly restricted to butterflies and has been duplicated in all Heliconius species. Although several CYP405A copies were found in the Sapho clade, most of them lack structurally important P450 domains, which explains the loss of biochemical plasticity via specialization in CG sequestration. This is one of the few examples of plasticity-first evolution in which the genetic mechanisms associated with its refinement are known.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13494554/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148701861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimating the evolutionary fitness of specific synonymous codon changes.","authors":"Vitor A C Pavinato, Jody Hey","doi":"10.1093/molbev/msag199","DOIUrl":"10.1093/molbev/msag199","url":null,"abstract":"<p><p>Synonymous mutations do not alter proteins but undergo natural selection in many species. For Drosophila melanogaster, reports on selection strength vary from undetectable to surprisingly strong. Here we apply a new method to estimate the population selection coefficient (2Ns) for all 134 ordered pairs of synonymous codon changes. The method uses ratios of site frequency spectra for synonymous codon changes and matched neutral changes, avoiding reliance on divergence data or codon frequencies and remaining relatively insensitive to demographic history. Results indicate that natural selection on synonymous codons is weak, with |2Ns|<2.30 for all pairs of codons and |2Ns|<1 for 49% of codon changes. Despite being derived solely from polymorphism data, codon fitness estimates are strongly correlated with observed codon frequencies. A selection-mutation-drift model based on these estimates accurately predicts codon usage, while a model based on mutation alone fails. Codon fitness estimates also predict expression-associated codon usage, with higher-fitness codons used more often in highly expressed genes. However, the effect of expression on selection strength is modest, with a 10-fold increase in expression predicted to increase the average strength of selection on synonymous codons by only 14%. Finally, we detect clear signs that selection favors codon changes that stabilize mRNA secondary structure. The convergence of multiple independent lines of evidence validates this polymorphism-based approach and provides a coherent framework for understanding selection on synonymous site evolution.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13494555/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148707030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Repeated mutation of a GT92 glycosyltransferase gene confers antiviral resistance in two Caenorhabditis species.","authors":"Aurélien Richaud, Gaotian Zhang, Cigdem Alkan, Daria Martynow, Tony Bélicard, Nanako Takeda, Eillen Tecle, Marie-Anne Félix","doi":"10.1093/molbev/msag208","DOIUrl":"10.1093/molbev/msag208","url":null,"abstract":"<p><p>Host-pathogen interactions evolve rapidly within species, providing natural genetic resources for the identification of specific ecological interaction factors. We previously identified RNA viruses that infect the nematodes Caenorhabditis elegans and Caenorhabditis briggsae in a species-specific manner. Wild strains of both host species demonstrate ample variation in viral sensitivity. Here we use recombinant inbred lines and pool-sequencing approaches to genetically map a major resistance locus in the C. elegans MY10 strain, narrowing down its position by CRISPR/Cas9-mediated recombination and testing candidates by genome editing. A rare non-synonymous polymorphism in the gtnt-1 gene, encoding a putative glycosyltransferase of the GT92 family, causes resistance to viral infection in MY10. Loss-of-function gtnt-1 alleles conferred host protection only at late developmental stages, highlighting the importance of multigenerational assays capturing the full course of viral infection and transmission. Viral resistance through gtnt-1 mutation occurred repeatedly in C. elegans, with diverse alleles each remaining at low frequency (<1%). Furthermore, leveraging closely related C. briggsae strains differing in viral susceptibility, we find that repeated loss-of-function alleles of the Cbr-gtnt-1 ortholog similarly enhanced resistance and host fitness upon infection. In conclusion, recurrent evolution in two host species of loss-of-function alleles of gtnt-1 orthologs leads to viral resistance. The gtnt-1 gene being conserved between Caenorhabditis species, these repeated inactivation events provide a case of transient ecological adaptation to a pathogen through recurrent mutation of the same gene in two species. The low population frequencies of resistant alleles point to a changing eco-evolutionary context that prevents their spread in populations.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13520123/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148758613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolutionary dynamics of the arthropod molting machinery.","authors":"Giulia Campli, Sagane Joye, Olga Volovych, Asya V Novikova, Ariel D Chipman, Marc Robinson-Rechavi, Robert M Waterhouse","doi":"10.1093/molbev/msag181","DOIUrl":"10.1093/molbev/msag181","url":null,"abstract":"<p><p>Exoskeletons define arthropods, providing support for segmented bodies and appendages while protecting against environmental stress and predation. Although ubiquitous, this evolutionarily variable feature has enabled arthropods to occupy diverse lifestyles and ecological niches, contributing to their unrivaled diversity. Because the chitinous cuticle is rigid, exoskeletons must be periodically shed and replaced as animals grow. Arthropods therefore develop through discrete molts, with conserved phases that progress from pre-molt preparation to ecdysis and post-molt maturation. These are tightly regulated developmental transitions controlled by a molecular toolkit comprising neuropeptides, hormone-synthesizing enzymes, receptors, and the early, fate, and late gene sets that activate and execute the molting process. Although genetic studies in model species have identified many components, major knowledge gaps remain, especially in noninsect arthropods. Advances in genome sequencing now enable comparative genomic analyses across diverse, previously understudied arthropod lineages to begin to address these gaps. We present a comprehensive comparative genomic survey of arthropods, sampling all four subphyla: Chelicerata, Myriapoda, Crustacea, and Hexapoda. Orthology inference and gene copy-number analyses contrast stable and dynamic components of the molting machinery across the phylum. Ancestral state reconstructions and phylogenetic reconciliations reveal gene duplication and loss dynamics and the evolutionary histories of key molting gene families. The inclusion of newly generated myriapod genomes addresses a major taxonomic gap and enables inferences of gene repertoire changes in the Mandibulata ancestor. The broad taxonomic representation enables a phylum-wide assessment to systematically evaluate, refine, and revise current understanding of the evolutionary dynamics of the molting genetic toolkit.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13449613/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148592649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantifying the predictability of evolution by analysis of coalescent rate variation.","authors":"Erik Volz, Xavier Didelot","doi":"10.1093/molbev/msag195","DOIUrl":"10.1093/molbev/msag195","url":null,"abstract":"<p><p>We investigate the predictability of evolution in terms of the phylogenetic placement of new lineages. This leads us to develop a class of coalescent models that relax neutrality by allowing the rate of coalescence to vary as a continuous heritable trait. In this setting, each lineage has a relative propensity to coalesce, with coalescent odds ratios defined from the product of pairwise propensities. Estimated coalescent odds provide a statistic that captures variation in lineage growth and are informative about the strength of natural selection acting on individual lineages. A number of practical statistical methods are then developed: techniques to adjust for biased and nonuniform sampling; procedures to automatically calibrate hyperparameters governing the evolution of coalescent propensity; and methods for clustering phylogenies into sets that delineate clades according to coalescent propensity. Simulations show sensitivity of these methods to detecting small selective effects acting on rare variants and strong robustness to imbalanced sampling. We demonstrate these methods using two datasets reflecting microbial populations evolving under strong selection. First, we examine a large set of Neisseria gonorrhoeae genomes and show that lineages with high coalescent odds feature a unique antibiotic resistance pattern, which presaged its subsequent expansion. We then reanalyze SARS-CoV-2 data in combination with independent estimates of reproduction numbers corresponding to major variants of concern 2020-2023. This indicates that coalescent odds can function as an excellent tree-based proxy for relative fitness of major SARS-CoV-2 lineages.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13483991/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148722999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel female reproductive organ differentiates insemination and postmating responses in bedbugs.","authors":"Birte M Martens, Caitlin E McDonough-Goldstein, Oliver Otti, Susanne Broschk, Lucas Kullmann, Klaus Reinhardt, Martin D Garlovsky","doi":"10.1093/molbev/msag169","DOIUrl":"10.1093/molbev/msag169","url":null,"abstract":"<p><p>Following the evolution of internal fertilization, the female reproductive tract became the site of two major reproductive interactions, the insemination response and the long-term postmating response. However, our understanding of these two responses is hampered by the fact they coincide in most animals. Traumatic insemination in the common bedbug (Cimex lectularius) presents a unique opportunity to disentangle these effects because females have evolved a novel organ, the mesospermalege, which is the site of insemination, while sperm do not arrive in the reproductive tract until several hours after mating. Here, we show that the mesospermalege exhibits a gene expression profile consistent with functions of the insemination response, including immune responses, that are normally found in the lower reproductive tract in other insect species. We then show that the postmating response in the lower female reproductive tract of bedbugs is delayed, coinciding with the movement of sperm through the female, suggesting that the postmating response has evolved in response to sperm receipt independent of intromission and insemination. Finally, we show male seminal fluid genes are expressed in the female, previously only demonstrated in Drosophila. Seminal fluid genes are more highly expressed in the mesospermalege than the reproductive tract, suggesting co-expression has evolved as part of the insemination response. Our results provide insights into the evolution of novel organs, reproductive traits, and female postmating gene expression in a global pest with an unusual reproductive biology.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":"43 8","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13437043/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148685245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phylogenetic ancestry of Metamonada proteins points to a common origin of mitochondria in all eukaryotes.","authors":"Kristína Záhonová, Pavel Doležal, Jan Tachezy, Julius Lukeš, Dave Speijer, Vladimír Hampl","doi":"10.1093/molbev/msag175","DOIUrl":"10.1093/molbev/msag175","url":null,"abstract":"<p><p>Hypotheses concerning eukaryogenesis, the evolution of eukaryotic cells, differ in the relative timing of mitochondrial acquisition. Recently, a serial endosymbiotic hypothesis proposed that hydrogenosomes and mitosomes (MROs) in Metamonada originated from an independent endosymbiosis, later replaced by Alphaproteobacteria-related mitochondria, contradicting the paradigm of mitochondrial presence in the last eukaryotic common ancestor. This serial endosymbiotic hypothesis implicitly predicts the scarcity of alphaproteobacterial genes from Metamonada genomes, because they never contained this endosymbiont. We tested this prediction using a set of 1,399 and 97 proteins inferred for the Metamonada ancestor and confined to their MROs, respectively. We detected five and 14 orthologous groups (OGs) with alphaproteobacterial affiliation in the respective datasets. None of these OGs was present in oxymonads, a Metamonada subgroup lacking MROs, thus serving as blank references. Our data are therefore consistent with the ruling paradigm that mitochondria and MROs originated from an Alphaproteobacterium during a single common endosymbiosis.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13428257/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148471733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and impacts of ploidy variation in the coral Pocillopora acuta in Hawai'i.","authors":"Erika C Johnston, Carlo Caruso, Tahirih Perez, Spencer Miller, Cameron Lau, Crawford Drury","doi":"10.1093/molbev/msag198","DOIUrl":"10.1093/molbev/msag198","url":null,"abstract":"<p><p>Differences in ploidy impact fitness, shaping adaptation and evolutionary trajectories. Although polyploidy has been documented in corals, the mechanisms that give rise to polyploidy and the phenotypic consequences of this variation are unknown. We established a model population of 326 Pocillopora acuta colonies in Kāne'ohe Bay, Hawai'i, and used RAD sequencing of these samples and historical collections to define clonal lineages, ploidy state, and mechanistic origin of polyploidy in each colony. We also measured growth, morphometrics, thermal tolerance, and fecundity in common-gardened corals. Here, we show that triploidy in P. acuta likely originated via allopolyploidy via hybridization between P. acuta and its sister species, P. damicornis. Triploids were present in this population before and after the 2014/2015 bleaching events, becoming the dominant ploidy on contemporary reefs (>60% of genotypes). These bleaching events did not select for triploid genotypes; however, relative triploid abundance may have increased in part due to higher growth rates compared to diploids. Both ploidies released larvae on the same lunar cycle and there was no difference in photosynthetic efficiency during heat stress, but triploid colonies experienced greater mortality at lower levels of stress, suggesting a host-derived fitness consequence influenced by ploidy state. This work highlights a cryptic source of variance in coral fitness, with important implications for understanding their ecology and evolution.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13487636/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148685255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Population structure and punctuated genomic hyper-diversity in Caenorhabditis briggsae.","authors":"Nicolas D Moya, Bowen Wang, Robyn E Tanny, Michael E G Sauria, Lance M O'Connor, Ayeh Khorshidian, Ryan McKeown, Charlie Gosse, Clayton M Dilks, Timothy A Crombie, Gaotian Zhang, Emha Rais, Lise Frézal, Viet Dai Dang, Elkana Haryoso, Mia P Devi, Clotilde Gimond, Daniel E Cook, Jung-Chen Hsu, Amanda O Shaver, Stefan Zdraljevic, Aurélien Richaud, Tongshu Wen, Aatira Mehraj, Sharanya H, Karthick Raja Arulprakasam, Emily J Koury, Nicole M Roberto, Etta S Schaye, Varsha Singh, Hagus Tarno, Michael Ailion, Annalise B Paaby, Zhongying Zhao, Asher D Cutter, John Wang, Matthew V Rockman, Marie-Anne Félix, Christian Braendle, Erik C Andersen","doi":"10.1093/molbev/msag202","DOIUrl":"10.1093/molbev/msag202","url":null,"abstract":"<p><p>Comparative genomics provides a powerful framework to uncover the molecular and evolutionary mechanisms that shape genetic diversity, revealing how shared or lineage-specific processes influence their evolutionary trajectories. The nematode Caenorhabditis briggsae is distributed world-wide and is a comparative model to Caenorhabditis elegans in the biology of development, cellular mechanisms, neurobiology, complex trait mappings, and evolution. Following massive collection efforts by the nematode research community, we present the isolation of over 1,900 wild strains and analyses of genome sequences that catalog over six million single-nucleotide and insertion-deletion variants. These resources provide a powerful means to interrogate the causal genetic bases of phenotypic variation. Additionally, we describe C. briggsae population structure and discover new, genetically distinct groups within this primarily self-fertilizing species, including groups of highly related strains sampled across entire continents. We leveraged expansive genetic variation to decipher the effects of linkage and selection on the distribution of genetic diversity across the genome and across geographic regions. Within the species, we find genomic regions with extremely high levels of genetic variation similar to hyper-divergent regions found in C. elegans and other species. These regions harbor new genes and variation enriched for environmental sensing and pathogen responses. Based on comparisons to the outbreeding sister species Caenorhabditis nigoni, we conclude that long-term balancing selection has maintained substantial functional variation, likely associated with ecological variation, within C. briggsae since its divergence from an outbreeding ancestor. Overall, this massive strain resource enables future comparative genetics studies, including genome-wide association study contrasts between Caenorhabditis species.</p>","PeriodicalId":18730,"journal":{"name":"Molecular biology and evolution","volume":" ","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13524100/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148725427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}