{ "abstract": "Invasive species threaten both ecological systems and economies. Successful establishment is governed partly by demographic stochasticity, where random individual-level variation can significantly influence invasion dynamics. A critical factor is the Allee effect, which describes reduced population growth at low densities, potentially serving as a barrier to persistence. Size-dependent growth and survival further shape outcomes based on the size distribution of individuals within the population. To address these complexities, we developed a population-level model integrating an Integral Projection Model (IPM) for the expected size distribution with an Allee effect for recruitment dynamics and a branching process to account for demographic stochasticity. We applied this framework to Silver Carp (Hypophthalmichthys molitrix), a species established in the Upper Mississippi River system that poses significant risk of expanding into the Great Lakes. Our analysis compared temporal dynamics and population-size distributions under hypothetical introduction scenarios for large adult and smaller subadult fish. In both cases, initial population size relative to the Allee threshold was a critical determinant of establishment probability, with introductions below the threshold requiring stochastic growth across a critical biomass boundary before self-sustaining dynamics could take hold. Sensitivity analysis further indicated that per-spawner recruitment played a compounding role in invasion risk: higher recruitment rates reduced the critical introduction size for establishment and compressed the time to self-sustaining population size, jointly broadening the window of invasion risk. These findings highlight the framework’s potential for invasion assessments and offer insights into how Allee effects, size structure, and recruitment rates interact to govern establishment outcomes, while underscoring the need for species-specific parameter estimates before quantitative outputs can guide management decisions. Author summary: Invasive species can cause lasting ecological and economic damage, yet many introduced populations disappear before becoming established. Understanding why some succeed while others fail is therefore important for preventing future invasions. Small populations face particular challenges, since chance differences in survival and reproduction can determine their fate, and population growth is often difficult when too few individuals are present. We developed a model that tracks how the sizes of individuals in a population change over time while accounting for reduced growth at low population sizes and the role of chance. We applied it to silver carp, an invasive fish already established in parts of the Upper Mississippi River system and considered a potential threat to the Great Lakes. Across the scenarios we examined, the strongest predictor of establishment was whether the introduced population started above a critical population level. Populations that produced more offspring per spawner also established more easily and more quickly. Our approach may help assess invasion risk, though reliable predictions for any given species will require species-specific measurements before the results can guide management.", "abstract_shown": true, "affiliations": [ "Mathematics & Statistics Department, University of Wisconsin - La Crosse, La Crosse, Wisconsin, United States of America", "River Studies Center, University of Wisconsin - La Crosse, La Crosse, Wisconsin, United States of America", "U.S. Geological Survey, Ecosystems Mission Area, Reston, Virginia, United States of America", "Kaskaskia Biological Station, Illinois Natural History Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Sullivan, Illinois, United States of America", "Minnesota Department of Natural Resources, St. Paul, Minnesota, United States of America", "U.S. Fish and Wildlife Service, La Crosse Fish and Wildlife Conservation Office, Onalaska, Wisconsin, United States of America", "Department of Natural Resource Management, South Dakota State, Brookings, South Dakota, United States of America" ], "article_type": "Research Article", "arxiv": null, "author_total": 7, "authors": [ { "affs": [ 0 ], "name": "James P. Peirce" }, { "affs": [ 1 ], "name": "Cynthia S. Tam" }, { "affs": [ 2 ], "name": "Joseph J. Parkos" }, { "affs": [ 3 ], "name": "Grace L. Loppnow" }, { "affs": [ 4 ], "name": "Mark W. Fritts" }, { "affs": [ 5 ], "name": "Alison A. Coulter" }, { "affs": [ 6 ], "name": "Richard A. Erickson" } ], "bibtex": "https://research.draconitic.com/paper/95ys1s90m4p3e.bib", "cited_by": 0, "doi": "10.1371/journal.pesy.0000022", "fulltext_url": null, "id": "95ys1s90m4p3e", "issns": [ "3070-8141" ], "landing_url": "https://doi.org/10.1371/journal.pesy.0000022", "language": null, "licence": "CC-BY-4.0", "licence_label": "CC BY 4.0", "licence_source": "journal", "licence_url": "https://creativecommons.org/licenses/by/4.0/", "metadata_licence": null, "native_subjects": [ [ "openalex", "2309|Fish Ecology and Management Studies" ], [ "plos", "/Biology and life sciences/Developmental biology/Modes of reproduction/Sexual reproduction/Spawning" ], [ "plos", "/Biology and life sciences/Ecology/Population ecology/Allee effect" ], [ "plos", "/Biology and life sciences/Organisms/Eukaryota/Animals/Vertebrates/Fish/Freshwater fish" ], [ "plos", "/Biology and life sciences/Organisms/Eukaryota/Animals/Vertebrates/Fish/Osteichthyes/Carps" ], [ "plos", "/Biology and life sciences/Population biology/Population ecology/Allee effect" ], [ "plos", "/Biology and life sciences/Population biology/Population metrics/Population size" ], [ "plos", "/Biology and life sciences/Zoology/Animals/Vertebrates/Fish/Freshwater fish" ], [ "plos", "/Biology and life sciences/Zoology/Animals/Vertebrates/Fish/Osteichthyes/Carps" ], [ "plos", "/Earth sciences/Marine and aquatic sciences/Aquatic environments/Freshwater environments/Rivers" ], [ "plos", "/Earth sciences/Marine and aquatic sciences/Bodies of water/Rivers" ], [ "plos", "/Ecology and environmental sciences/Aquatic environments/Freshwater environments/Rivers" ], [ "plos", "/Ecology and environmental sciences/Ecology/Population ecology/Allee effect" ], [ "plos", "/Ecology and environmental sciences/Species colonization/Invasive species" ], [ "plos", "/Research and analysis methods/Research design/Survey research/Census" ] ], "openalex": "W7211960028", "pdf_url": null, "pmcid": null, "pmid": null, "published": "2026-09-08", "publisher": "Public Library of Science", "ris": "https://research.draconitic.com/paper/95ys1s90m4p3e.ris", "sources": [ { "first_seen": "2026-10-30T12:17:56Z", "native_id": "10.1371/journal.pesy.0000022", "source": "plos", "url": "https://doi.org/10.1371/journal.pesy.0000022" } ], "subjects": [ { "field": "biology", "origin": "plos:developmental biology", "subfield": "developmental-biology" }, { "field": "biology", "origin": "plos:ecology", "subfield": "ecology" }, { "field": "biology", "origin": "plos:zoology", "subfield": "zoology-behaviour" } ], "title": "Combining branching processes and Allee effects into an integral projection model to assess invasion risk", "title_text": "Combining branching processes and Allee effects into an integral projection model to assess invasion risk", "type": "peer-reviewed", "updated_at": "2026-10-30T12:17:56Z", "url": "https://research.draconitic.com/paper/95ys1s90m4p3e", "venue": "PLOS Ecosystems", "versions": [] }