Reproductive Isolation and Differential Introgression Shape the Genomic Landscape of the Red Alga Amansia glomerata in the Hawaiian Archipelago

Reproductive Isolation and Differential Introgression Shape the Genomic Landscape of the Red Alga Amansia glomerata in the Hawaiian Archipelago | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Reproductive Isolation and Differential Introgression Shape the Genomic Landscape of the Red Alga Amansia glomerata in the Hawaiian Archipelago Lauric Reynes, Alison Sherwood, James Fumo This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9015118/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Speciation in marine environments is inherently complex, and the mechanisms underlying the evolution of reproductive isolation remain a fundamental yet understudied challenge in macroalgae. This study investigates two lineages of the marine red alga Amansia glomerata around Oʻahu, Hawaiʻi, to test the hypothesis that lineage boundaries are maintained by strong reproductive barriers resulting from historical geographic isolation. Using genomic sequencing (ddRAD), fine-scale spatial transects, and demographic modeling, we characterized lineage spatial structure and genomic divergence. Our results revealed that lineages remained strongly differentiated across the genome, even where they co-occurred across extensive sympatric regions. Demographic analyses supported a scenario of allopatric divergence followed by secondary contact, likely driven by Pleistocene sea-level fluctuations within the Hawaiian Archipelago. The absence of recombinant hybrids, together with numerous loci acting as barriers to gene flow, is consistent with the evolution of postzygotic isolation. Nevertheless, genomic signatures of introgression indicate that gene flow during secondary contact was spatially structured around the island and heterogeneous across the genome, revealing differential permeability of lineage boundaries at the time of contact. While our findings highlight allopatric divergence and intrinsic reproductive barriers as major drivers of speciation in this system, the potential role of ecological differentiation remains to be explored. Overall, this study provides pioneering insights into the genomics of speciation in Hawaiian seaweeds and underscores their potential as a model system for marine speciation. Earth and environmental sciences/Ecology/Evolutionary ecology Biological sciences/Evolution/Evolutionary genetics Full Text Additional Declarations There is no duality of interest Supplementary Files SUPPLEMENTARYMS.pdf Supplemental Material Graphicalabstract.pdf Graphical abstract Cite Share Download PDF Status: Under Review Version 1 posted Review # 3 received at journal 04 May, 2026 Review # 1 received at journal 23 Apr, 2026 Review # 2 received at journal 21 Apr, 2026 Reviewer # 3 agreed at journal 09 Apr, 2026 Reviewer # 2 agreed at journal 31 Mar, 2026 Reviewer # 1 agreed at journal 30 Mar, 2026 Reviewers invited by journal 30 Mar, 2026 Editor assigned by journal 02 Mar, 2026 First submitted to journal 02 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9015118","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":599666832,"identity":"0d88dd0a-3da9-4c2e-a52b-a6cadf670443","order_by":0,"name":"Lauric Reynes","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzUlEQVRIiWNgGAWjYBACPigtZwAiE0DkAQJa2KC0MelaEjfAhQhqkT58TLqgoi59O/sZww8PChjk+G4kENDCl5YmPePM4dydPTnGEkCHGUsS1MLDYybN23YgdwMQgbQkbiCshf+bNO+/unSD8283/wBqqSdCCw+bNG8Dc4LBjdxtIFuADIJa2IyteY4dNtxw4/03iwQDCcOZZx7g18LPw/zwNk9NnbzB+bTkmz/+2MjzHSdgCxCwSCBxJHAqQwbMH4hSNgpGwSgYBSMXAACjRUBOtWCatwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-0223-4332","institution":"University of Hawaii","correspondingAuthor":true,"prefix":"","firstName":"Lauric","middleName":"","lastName":"Reynes","suffix":""},{"id":599666833,"identity":"5ba09b4d-7402-4b8d-8682-10265b686650","order_by":1,"name":"Alison Sherwood","email":"","orcid":"","institution":"University of Hawaii","correspondingAuthor":false,"prefix":"","firstName":"Alison","middleName":"","lastName":"Sherwood","suffix":""},{"id":599666834,"identity":"0c80c1bd-1bf2-42c7-a8b6-d030e6423781","order_by":2,"name":"James Fumo","email":"","orcid":"","institution":"University of Hawaii","correspondingAuthor":false,"prefix":"","firstName":"James","middleName":"","lastName":"Fumo","suffix":""}],"badges":[],"createdAt":"2026-03-03 03:00:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9015118/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9015118/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104780417,"identity":"d3b59d79-0d45-4510-a985-9e36b9fc101c","added_by":"auto","created_at":"2026-03-17 07:52:51","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":902944,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9015118/v1_covered_ab35f93a-95e2-433f-860f-0ed2558061ec.pdf"},{"id":104476176,"identity":"abc4bc9c-cf19-4291-8d43-515682ee8128","added_by":"auto","created_at":"2026-03-12 08:20:57","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1122683,"visible":true,"origin":"","legend":"Supplemental Material","description":"","filename":"SUPPLEMENTARYMS.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9015118/v1/eaf452bb6067de47ac048b0f.pdf"},{"id":104476175,"identity":"909dcc41-7257-47c1-a53d-3c7f5314239d","added_by":"auto","created_at":"2026-03-12 08:20:57","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":163445,"visible":true,"origin":"","legend":"Graphical abstract","description":"","filename":"Graphicalabstract.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9015118/v1/f548ecbed9140f19c3b0c395.pdf"}],"financialInterests":"There is no duality of interest","formattedTitle":"Reproductive Isolation and Differential Introgression Shape the Genomic Landscape of the Red Alga Amansia glomerata in the Hawaiian Archipelago","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"heredity","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"hdy","sideBox":"Learn more about [Heredity](http://www.nature.com/hdy/)","snPcode":"41437","submissionUrl":"https://mts-hdy.nature.com/cgi-bin/main.plex","title":"Heredity","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9015118/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9015118/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Speciation in marine environments is inherently complex, and the mechanisms underlying the evolution of reproductive isolation remain a fundamental yet understudied challenge in macroalgae. 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