Fight club, or the story of the invasion of two marine blue crab species in the Mediterranean Sea

Fight club, or the story of the invasion of two marine blue crab species in the Mediterranean Sea | 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 Research Article Fight club, or the story of the invasion of two marine blue crab species in the Mediterranean Sea Guillaume Marchessaux, Vojsava Gjoni, Raouia Ghanem, Wafa Rjiba Bahri, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7419650/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Climate change and anthropogenic pressures are driving the expansion of marine species, influencing organism performance, population dynamics, and ecosystem structure. In the Mediterranean Sea, the invasive American blue crab, Callinectes sapidus , and the Red Sea blue crab, Portunus segnis , are expanding their ranges in response to accelerated ocean warming. This study analyzes their Thermal Performance curves (TPCs) to predict co-occurrence and dominance under climate scenarios. Callinectes sapidus thrives in cooler temperatures, while P. segnis is better adapted to warmer environments. These patterns indicate a latitudinal partitioning driven by temperature tolerance, with only limited temporal overlap during the warmest months. Notably, while coexistence in 2023 was rare and spatially restricted, by 2050 these zones become more extensive and frequent, especially from July through October, indicating a future rise in interspecific interactions. These future projections indicate that rising temperatures will favor P. segnis , increasing competition and co-occurrence with C. sapidus , particularly in summer. The study highlights the importance of understanding temperature-driven physiological traits in shaping invasive species interactions and developing tools for management. Maps generated from TPCs and thermal dominance indices inform risk management plans and conservation efforts, helping to mitigate the ecological and socio-economic impacts of these invasive species. Animal Physiology Marine and Freshwater Ecology Conservation Biology Callinectes sapidus Portunus segnis Invasive species management Climate change Figures Figure 1 Figure 2 Figure 3 Figure 4 1 Introduction The expansion of marine species results from climate change and human activities (Gallardo et al. 2017 ; Ramos et al. 2018 ; Seebens et al. 2021 ). The global rise in ocean temperatures influences organism performance, population dynamics, and ecosystem structure (Yao & Somero 2014 ), leading to a migration of species toward the poles and temperate zones in response to their adaptive capacity (Sarà et al. 2013 ). Changes in temperature regimes, surface currents, ice cover, and other essential processes promote both natural and anthropogenic species dispersal, allowing some species to survive and establish themselves in previously unsuitable areas (Hellmann et al. 2008 ; Bellard et al. 2018 ; Chan et al. 2019 ; Occhipinti-Ambrogi 2021 ). Temperature plays a key role in biochemical and metabolic reactions, determining organisms’ thermal tolerance limits, phenology, and distribution (Walter & Graf 2002 ; Helmuth 2009 ; Freitas et al. 2010 ; Yao & Somero 2014 ; DeLong et al. 2018 ). Variations in environmental exposure explain the diversity of physiological responses observed, highlighting the importance of assessing the effects of climate change across all coastal systems (Cooley et al. 2009 ). Metabolism is a fundamental factor to consider in organisms, as it represents the sum of all potential biochemical work occurring within an organism (DeLong et al. 2018 ). Metabolism governs vital functions throughout an organism's life, including growth, reproduction, maintenance, and activity (Kontopoulos et al. 2024 ), which, in turn, influence population dynamics and long-term sustainability. Metabolism is a universal function across all living organisms, from bacteria to whales, including photosynthetic organisms, and operates at every biological level (DeLong et al. 2018 ; Kontopoulos et al. 2024 ). One of the most common measures in metabolism studies is the assessment of thermal performance, particularly in ectothermic species—organisms whose body temperature aligns with their environment. Ectotherms typically show an increase in metabolic rate as temperature rises, reaching a peak, referred to as the optimum, followed by a decline beyond this thermal optimum (Verberk et al. 2016 ; Rezende & Bozinovic 2019 ). Understanding the temperature dependence of metabolic rate requires analyzing thermal performance curves (TPCs), which capture peak metabolic rate (Rmax) (Angilletta Jr 2006 ; Molnar et al. 2008 ; Angilletta & Angilletta 2009 ). The decline in metabolic rate beyond the thermal optimum (Topt) may result from reduced enzymatic efficiency at higher temperatures. Metabolic performance is influenced by substrate delivery, enzyme kinetics, catalytic efficiency, and the structural integrity of oxidative phosphorylation sites (Angilletta & Angilletta 2009 ). TPCs offer an integrated view of how organisms perform across temperature gradients. In the context of climate change, TPCs serve as key indicators of species’ thermal fitness. Four main models—“hotter is better,” “metabolic cold adaptation,” “colder is better,” and “peak matching”—help predict species’ responses to temperature change (DeLong et al. 2018 ). Comparing TPCs allows assessment of species dominance or coexistence, and has proven useful for predicting invasive species’ distributions and supporting early detection and management. In 2023, exceptional warming of Mediterranean waters (Wedler et al. 2023) facilitated the rapid expansion of the invasive American blue crab Callinectes sapidus (Rathbun, 1896) into marine, brackish, and freshwater habitats across Mediterranean countries (Castriota et al. 2024 ). Italy’s entire coastline was affected, while Tunisia saw expansion into the Gulf of Gabès (J. Ben Souissi, pers. obs.). The same year, the Red Sea swimming blue crab, Portunus segnis (Forskål, 1775), native to the Indo-Pacific, was reported further North than ever before—along Spain’s Gulf of Cadiz (de Carvalho-Souza et al. 2023) and the Italian Adriatic coast (Grati et al. 2023 ). Until then, P. segnis had been confined to the southeastern Mediterranean especially from Tunisia to Turkey. This northward shift suggests possible future co-existence of P. segnis and C. sapidus , which may intensify impacts on ecosystems and socio-economic sectors. We hypothesize that their co-existence could exacerbate socio-economic challenges, particularly for artisanal fisheries and shellfish farming, by increasing damage to gear and competition for resources. The primary objective of our study is therefore to assess the potential for thermal niche-driven co-existence between P. segnis and C. sapidus , and to develop predictive tools that can anticipate and map their co-occurrence. By doing so, we aim to identify priority areas for monitoring and inform proactive management strategies to mitigate the ecological and economic risks posed by these two invasive species under current and future climate scenarios. The present study aims to analyze the distribution of non-native species based on their TPCs and propose a tool to assess the species co-occurrence and dominance based on their metabolic responses to temperature. To do this, we used experimental measurements of metabolic performance of two invasive blue crab species and tested and verified whether temperature-induced metabolic differences influence species distribution, dominance and co-occurrence. Our research focuses on two invasive blue crab species from the Portunidae family in the Mediterranean: the Atlantic blue crab, Callinectes sapidus , and the Red Sea blue crab, Portunus segnis . While previous studies have examined their ecological impacts and spread, there is still a gap in understanding how their metabolic responses to temperature influence their distribution, co-occurrence, and competitive dynamics. By analyzing their thermal performance curves (TPCs) and developing a predictive tool, this study aims to bridge that gap and provide insights into the role of temperature-driven physiological traits in shaping invasive species interactions. 2 Materials and Methods 2.1 Thermal performance curve models To evaluate co-occurrence and dominance scenarios between Callinectes sapidus and Portunus segnis , we analyzed their thermal performance curves (TPCs) from Marchessaux et al. ( 2022 , 2024 ). Both TPCs were plotted using the original curve equations and compared using the framework by DeLong et al. ( 2018 ) (“hotter is better,” “cold adaptation,” etc.). We developed a dominance index (D), calculated as the difference between species' metabolic rates at each temperature. Negative D values indicate C. sapidus dominance, positive values indicate P. segnis dominance, and D = 0 indicates co-occurrence. The D equation was applied to temperature layers to spatially map dominance and coexistence across the Mediterranean. To test model robustness, we used a generalized additive model (GAM) with spline smoothing via the gam() function in the mgcv package (Wood 2017 ) in R Studio (v2024.12.0). We also used LOESS regression to assess the sensitivity of predictions to temperature bounds, visualizing outputs across a standardized temperature grid. 2.2 Mapping the current and future thermal suitability The D index curve was applied to predict the distribution of C. sapidus and P. segnis under current (2023) and future (2050) climate scenarios (RCP 4.5 and RCP 8.5; CMIP5 models, https://cds.climate.copernicus.eu/ ). Dominance values were extracted monthly for 16 Mediterranean countries. Annual proportions of species dominance and co-occurrence were mapped using R Studio (v2024.12.0) and QGIS (v3.10.7). Pie charts displayed these proportions, and a map showing percentage change from 2023 to 2050 highlighted national conservation priorities for C. sapidus , P. segnis , and their co-occurrence. 3 Results The metabolic respiration rate of the two species varies with temperature (Fig. 1 A). Callinectes sapidus reaches its maximum metabolic rate at 23.91°C, while Portunus segnis peaks at a higher temperature, 33.64°C, indicating better adaptation of P. segnis to warmer environments. At temperatures below approximately 23°C, C. sapidus has a metabolic advantage (red zone), but beyond this point, P. segnis becomes dominant (blue zone), with an increasing metabolic gap at higher temperatures (Fig. 1 B). This figure underscores the thermal differences in the physiological performance of the two species, reflecting their respective ecological. adaptations. In 2023, C. sapidus dominated most Mediterranean regions (Fig. 2 A). It was especially prevalent in the Western Mediterranean (France, Morocco, Spain, Italy), while P. segnis was more widespread in the Eastern Mediterranean (Greece, Turkey, Cyprus, Lebanon, Egypt, Tunisia). Co-occurrence was observed across the basin, with higher proportions in the Southeast (e.g., Egypt, Cyprus). Monthly trends (Fig. 2 B) showed C. sapidus present year-round, particularly from May to September in France. In contrast, P. segnis was dominant from April to October in Italy and from March to August in Tunisia, with similar patterns in Israel, Cyprus, and Egypt. Projections for 2050 under the RCP 8.5 scenario show shifting dominance patterns between Callinectes sapidus and Portunus segnis (Fig. 3 ). C. sapidus remains dominant in the Western Mediterranean (France, Spain, Italy), while P. segnis expands into regions where it was less prevalent in 2023 (Fig. 3 A). In the Eastern Mediterranean (Greece, Turkey, Cyprus), P. segnis remains prevalent but with increased co-occurrence with C. sapidus , suggesting west-to-east range expansion. Co-occurrence becomes more widespread (e.g., Algeria, Tunisia, Egypt), indicating overlapping habitats due to environmental shifts. The temporal evolution for 2050 (Fig. 3 B) shows a shift in monthly presence probabilities toward later in the year. For example, in France, peak C. sapidus presence may shift from May–September (2023) to June–October (2050). In Italy, P. segnis ’ presence, initially April–October, may extend to May–November. Co-occurrence periods also shift rightward, occurring later in the year in countries like Turkey, Tunisia, Spain, and Greece. These changes reflect climate-driven shifts in species’ phenology and potential increases in interspecific interactions, highlighting the need for updated management strategies in light of future overlap and competition between these invasive species. The percentage change between 2050 and 2023 highlights projected shifts in the distribution of C. sapidus , P. segnis , and their co-occurrence across the Mediterranean (Fig. 4 A). In the Western Mediterranean, countries like France, Spain, and Italy are expected to see an increase in C. sapidus , indicating range expansion or greater dominance. In contrast, Algeria, Tunisia, Libya, Egypt, and Israel show decreasing C. sapidus and co-occurrence, but increasing P. segnis , reflecting significant distributional changes. In the Eastern Mediterranean, Greece and Turkey are projected to experience a notable rise in P. segnis , suggesting continued eastward expansion. Overall, these trends underscore the dynamic nature of species distribution in response to climate change and highlight the need for adaptive, country-specific management strategies. Management needs vary latitudinally. Southern Mediterranean countries (e.g., Morocco, Algeria, Tunisia, Libya, Egypt, Israel) should prioritize P. segnis control. Similarly, Italy and Albania in the Adriatic Sea face growing P. segnis pressure. Spain, Croatia, Montenegro, Turkey, and Lebanon should focus efforts on C. sapidus . Greece and Cyprus, showing increases or persistent presence of both species, will require management strategies targeting both C. sapidus and P. segnis to mitigate ecological and socio-economic impacts. The Fig. 4 B, provides a detailed framework for managing the presence of two crab species, C. sapidus and P. segnis , in the Mediterranean region, focusing on their individual and co-occurring distributions based on the changes identified between 2050 and 2023. For C. sapidus and P. segnis , a decrease in their presence was not considered a priority for management efforts. However, an increase in C. sapidus and P. segnis populations requires management intervention to mitigate potential ecological impacts. When both species co-occur, management is required to address the combined ecological and socio-economic impacts, emphasizing the need for integrated strategies to limit negative outcomes. 3 situations were identified: If one of the two blue crab species was already present in a country, the recommended actions include monitoring blue crabs and quantifying their ecological impacts, implementing spatial control and fisheries management, and raising awareness about socio-ecological issues. It is the case for all Mediterranean countries, as C. sapidus is currently widespread. For countries where the species are not currently present, but are predicted to appear in the future, especially for P. segnis , early detection and rapid response mechanisms are crucial to prevent establishment and spread. If no changes were identified between 2050 and 2023, overall, proactive and adaptive management strategies to address the dynamic distribution of these crab species, aiming to limit their co-occurrence and the associated socio-ecological impacts are crucial, as underscored by the figure. If no change was identified between 2050 and 2023, i.e. the predicted presence of one or both blue crab species is the same in both scenarios, then management measures (situation 1) should be implemented on both species together. 4 Discussion Working on the metabolic values of species is essential to understanding their persistence and the possibility of coexistence between them. Metabolism, as a direct reflection of an organism's physiological functioning, conditions its performance, growth, reproduction and survival in a given environment (Brown et al. 2004 ). By comparing these values between species and as a function of temperature, it is possible to identify the most favorable environmental contexts to each. For example, some species perform better at higher temperatures, according to the “hotter is better” principle (Huey & Kingsolver 1989 ; DeLong et al. 2018 ), while others may benefit from colder environments (“colder is better”) if they maintain metabolic efficiency at lower temperatures (Angilletta et al. 2010 ). These dynamics make it possible to predict not only under which conditions a species is likely to persist, but also whether two species can coexist or whether one is likely to exclude the other due to a competitive advantage linked to metabolism (Tilman 1982 ; Dell et al. 2011 ). The study of metabolic values makes it possible to link individual physiological mechanisms to larger-scale ecological dynamics. Understanding the coexistence of Callinectes sapidus and Portunus segnis is crucial for predicting the ecological consequences of biological invasions in the Mediterranean Sea. Historically occupying distinct thermal niches, these two invasive crabs now increasingly overlap due to climate change, especially during warmer months. Consistent with the “hotter is better” hypothesis (DeLong et al. 2018 ), P. segnis , a tropical species, gains a competitive advantage under rising temperatures, potentially shifting species dominance in future scenarios. Both species are aggressive, opportunistic omnivores feeding on mollusks, crustaceans, and fish (Ryer 1987 ; Hosseini et al. 2014 ; Mancinelli et al. 2017 ; Chiesa et al. 2025 ). Their growing overlap intensifies competition for food, disrupts trophic interactions, and threatens native biodiversity (Mancinelli et al. 2017 ; Rabaoui et al. 2021 ). Studies show they alter food webs and may engage in interspecific and intraguild cannibalism, increasing ecological pressures. Using species distribution models and thermal performance curves, we identified current and future coexistence hotspots. These tools provide early warning indicators to guide detection, monitoring, and management. Our findings highlight the need to incorporate physiological traits and temperature-driven dynamics into invasion frameworks to address long-term ecological and socio-economic impacts. Portunus segnis ’ thermal advantage suggests a shift in competitive balance, challenging the assumption of stable coexistence. As both species increasingly impact fisheries—damaging gear and reducing fish stocks (Ben Souissi et al. 2017 )—their expanding presence could further strain ecosystems and livelihoods. Understanding and predicting their interactions is essential for effective policy and mitigation planning. The "multiple species invasion" hypothesis supports the idea that the effects of co-occurring non-indigenous species (NIS) on local communities may be greater, lesser, or negligible compared to the impact of each species in isolation, as demonstrated in plants (Kuebbing et al. 2014 ). Thus, a range of possible outcomes may arise from the interaction between these two blue crabs, from a facilitative cumulative scenario—commonly referred to as "invasion meltdown" where one species enhances the success of the other (Berglund et al. 2013 ) — to a scenario where their effects remain independent, with minimal interaction between them (Rauschert & Shea 2017 ). Previous studies suggest that the impact of two co-occurring NIS largely depends on the degree of their ecological niches overlap, reflected in their functional, life-history, and ecological traits (Ricciardi et al. 2013 ; Blackburn et al. 2019 ). Sheppard et al. ( 2018 ) suggested that the greater the similarity between two co-occurring alien species, the higher the invasion success of both, which may amplify their detrimental effects on local communities (Berglund et al. 2013 ). Furthermore, anthropogenic environmental changes may intensify these impacts by introducing new pathways for invasion (Sarà et al. 2018 ; Sheppard et al. 2018 ). In the Mediterranean, evidence suggests that the occurrence and population densities of invasive species are driven by rising temperature and the absence of natural competitors and predators (Raitsos et al. 2010 ; Hoffman 2014 ; Elliott et al. 2015 ). Our findings reinforce these observations, highlighting the role of climate change in shaping species interactions and invasion dynamics. The main outcome of the study of the coexistence of invasive blue crabs involved generating maps, cost-effective tools providing robust visualizations for early detection (useful for Early Detection and Rapid Response - EDRR - programs; (Harvey & Mazzotti 2019 ). These maps enable exploration of the potential geographic distribution of the two species and their overlapping areas, informing risk management plans (Tulloch et al. 2015 ). To facilitate stakeholder and manager understanding, a “cohabitation index” (Elleouet et al. 2014 ) was developed to infer blue crab hotspots based on distribution overlap. Additionally, to enhance EDRRs addressing C. sapidus and P. segnis , species distribution models (SDMs) were implemented using IPCC AR5 climate change scenarios (RCP 4.5 and RCP 8.5) to predict future occurrences of the two species up to 2050. This step provides a robust foundation for future conservation planning, helping predict effective multispecies management decisions and contributing valuable insights into community assembly (Sheppard et al. 2018 ). Knowledge of thermal limits is also valuable for selecting effective biocontrol agents and guiding community-based monitoring efforts through citizen science campaigns (Reaser et al. 2020 ). This information informs policy decisions, such as establishing quarantine zones or regulating the movement of goods between regions with differing thermal profiles (Venette et al. 2021 ). This current study offers critical information for developing targeted and sustainable management strategies to address invasions of C. sapidus and P. segnis . Based on the international recommendations for the management of both invasive blue crabs in the Mediterranean Sea (UNEP/MAP-SPA/RAC 2025 ) and by identifying coexistence zones and analyzing their distribution under different climate scenarios (RCP 4.5 and RCP 8.5), it becomes possible to prioritize control efforts in regions with the greatest ecological and socio-economic impact: One of the blue crab species is dominant or only present in the national territory : Decision-makers can therefore use the results obtained in our study to implement measures to control the species on a national level. In this case, prediction maps for current and future scenarios enable decision-makers to determine the areas where the species could expand (Marchessaux et al. 2022 , 2024 ). Using predictive maps, decision-makers could, for example, set up early species detection programs (EDRR) using citizen science, or regular monitoring of potential risk areas. Monitoring and anticipating the introduction of species on a national scale also requires precise, anticipatory regulations. Co-occurrence is identified in the national territory : regions where both species coexist could be targeted for intensive fishing measures to simultaneously reduce their densities (Azzurro et al. 2024 ). Additionally, understanding their habitat preferences and seasonal activity periods enables the design of species-specific traps or selective capture techniques to minimize bycatch of native species. To do that we need to develop acoustic telemetry to determine how the two species will interact and how they use the space in terms of habitats preferences, temperature referendum, and food availability. Insights into combined ecological impacts, such as resource competition and disruptions to trophic networks, can guide habitat restoration programs to bolster populations of resilient native species. Understanding this co-occurrence is crucial for identifying potential ecological and competitive mechanisms, particularly in shared environments. The study of ecological niche overlap between two invasive species is crucial for understanding and managing ecosystems. First, it allows for the evaluation of potential interactions between these species, thereby anticipating consequences for local biodiversity. By identifying areas of niche overlap, managers can target control efforts more effectively. This knowledge is critical for developing conservation and restoration strategies aimed at maintaining ecological balance and enhancing ecosystem resilience in the face of biological invasions. Declarations Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Authors Contributions G.M. conceived the ideas and hypotheses. G.M. analyzed the data with assistance from V.G., and M.C. for the management part; G.M. wrote the first version of the manuscript. The manuscript was edited, revised and approved by all authors. Data availability statement The data that support the findings of this study are available from the literature for the Thermal Performance Curve (Marchessaux et al., 2022 ( C. sapidus) , Marchessaux et al., 2024 ( P. segnis )), and the percentage and maps by contacting the corresponding author upon reasonable request. References Angilletta Jr, M.J. (2006). Estimating and comparing thermal performance curves. J. Therm. Biol. , 31, 541–545. Angilletta, M.J. & Angilletta, M.J. (2009). Thermal adaptation: a theoretical and empirical synthesis. Oxf. Univ. Press , 289. Angilletta, M.J., Cooper, B.S., Schuler, M.S. & Boyles, J.G. (2010). The evolution of thermal physiology in endotherms. Front. Biosci.-Elite , 2, 861–881. 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Distribution, abundance, and life history traits of the blue swimming crab Portunus segnis (Forskål, 1775) in the Saudi waters of the Arabian Gulf. Reg. Stud. Mar. Sci. , 101895. Raitsos, D.E., Beaugrand, G., Georgopoulos, D., Zenetos, A., Pancucci-Papadopoulou, A.M., Theocharis, A. & Papathanassiou, E. (2010). Global climate change amplifies the entry of tropical species into the Eastern Mediterranean Sea. Limnol. Oceanogr. , 55, 1478–1484. Ramos, J.E., Pecl, G.T., Moltschaniwskyj, N.A., Semmens, J.M., Souza, C.A. & Strugnell, J.M. (2018). Population genetic signatures of a climate change driven marine range extension. Sci. Rep. , 8, 1–12. Rauschert, E.S.J. & Shea, K. (2017). Competition between similar invasive species: modeling invasional interference across a landscape. Popul. Ecol. , 59, 79–88. Reaser, J.K., Burgiel, S.W., Kirkey, J., Brantley, K.A., Veatch, S.D. & Burgos-Rodríguez, J. (2020). The early detection of and rapid response (EDRR) to invasive species: a conceptual framework and federal capacities assessment. Biol. Invasions , 22, 1–19. Rezende, E.L. & Bozinovic, F. (2019). Thermal performance across levels of biological organization. Philos. Trans. R. Soc. B Biol. Sci. , 374, 20180549. Ricciardi, A., Hoopes, M.F., Marchetti, M.P. & Lockwood, J.L. (2013). Progress toward understanding the ecological impacts of nonnative species. Ecol. Monogr. , 83, 263–282. Ryer, C.H. (1987). Temporal patterns of feeding by blue crabs (Callinectes sapidus) in a tidal-marsh creek and adjacent seagrass meadow in the lower Chesapeake Bay. Estuaries , 10, 136–140. Sarà, G., Palmeri, V., Rinaldi, A., Montalto, V. & Helmuth, B. (2013). Predicting biological invasions in marine habitats through eco-physiological mechanistic models: a case study with the bivalve B rachidontes pharaonis. Divers. Distrib. , 19, 1235–1247. Sarà, G., Porporato, E.M., Mangano, M.C. & Mieszkowska, N. (2018). Multiple stressors facilitate the spread of a non-indigenous bivalve in the Mediterranean Sea. J. Biogeogr. , 45, 1090–1103. Seebens, H., Bacher, S., Blackburn, T.M., Capinha, C., Dawson, W., Dullinger, S., Genovesi, P., Hulme, P.E., van Kleunen, M. & Kühn, I. (2021). Projecting the continental accumulation of alien species through to 2050. Glob. Change Biol. , 27, 970–982. Sheppard, C.S., Carboni, M., Essl, F., Seebens, H., Consortium, D. & Thuiller, W. (2018). It takes one to know one: Similarity to resident alien species increases establishment success of new invaders. Divers. Distrib. , 24, 680–691. Tilman, D. (1982). Resource competition and community structure . Princeton university press. Tulloch, V.J., Tulloch, A.I., Visconti, P., Halpern, B.S., Watson, J.E., Evans, M.C., Auerbach, N.A., Barnes, M., Beger, M. & Chadès, I. (2015). Why do we map threats? Linking threat mapping with actions to make better conservation decisions. Front. Ecol. Environ. , 13, 91–99. UNEP/MAP-SPA/RAC. (2025). Best practices and management measures of the blue crabs in the Mediterranean by Guillaume Marchessaux . Ed. SPA/RAC. Tunis. Venette, R.C., Gordon, D.R., Juzwik, J., Koch, F.H., Liebhold, A.M., Peterson, R.K., Sing, S.E. & Yemshanov, D. (2021). Early intervention strategies for invasive species management: connections between risk assessment, prevention efforts, eradication, and other rapid responses. Invasive Species For. Rangel. U. S. Compr. Sci. Synth. U. S. For. Sect. , 111–131. Verberk, W.C.E.P., Bartolini, F., Marshall, D.J., Pörtner, H., Terblanche, J.S., White, C.R. & Giomi, F. (2016). Can respiratory physiology predict thermal niches? Ann. N. Y. Acad. Sci. , 1365, 73–88. Walter, K. & Graf, H.-F. (2002). On the changing nature of the regional connection between the North Atlantic Oscillation and sea surface temperature. J. Geophys. Res. Atmospheres , 107, ACL-7. Wood, S.N. (2017). Generalized additive models: an introduction with R . chapman and hall/CRC. Yao, C.-L. & Somero, G.N. (2014). The impact of ocean warming on marine organisms. Chin. Sci. Bull. , 59, 468–479. Additional Declarations The authors declare no competing interests. Supplementary Files Supplementary.docx Supplementary material Cite Share Download PDF Status: Posted Version 1 posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7419650","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":503260827,"identity":"95464cbf-de29-4180-9b89-146bfe673af4","order_by":0,"name":"Guillaume Marchessaux","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0001-5557-2274","institution":"Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, Marseille, France","correspondingAuthor":true,"prefix":"","firstName":"Guillaume","middleName":"","lastName":"Marchessaux","suffix":""},{"id":503260828,"identity":"159ee816-d660-4bac-9bb7-d9eb8d2ef64f","order_by":1,"name":"Vojsava Gjoni","email":"","orcid":"https://orcid.org/0000-0003-1740-6093","institution":"Department of Earth and Marine Science (DiSTeM), University of Palermo, Palermo, Italy","correspondingAuthor":false,"prefix":"","firstName":"Vojsava","middleName":"","lastName":"Gjoni","suffix":""},{"id":503260829,"identity":"8941b76d-155e-466b-8b36-2c130b6b2e6b","order_by":2,"name":"Raouia Ghanem","email":"","orcid":"https://orcid.org/0000-0001-6947-582X","institution":"National Institute of Agronomy of Tunisia (INAT), University of Carthage, Tunis, Tunisia","correspondingAuthor":false,"prefix":"","firstName":"Raouia","middleName":"","lastName":"Ghanem","suffix":""},{"id":503260830,"identity":"83a52351-38ff-4389-8ae2-713f0c99fc6f","order_by":3,"name":"Wafa Rjiba Bahri","email":"","orcid":"https://orcid.org/0000-0001-8416-8342","institution":"National Institute of Agronomy of Tunisia (INAT), University of Carthage, Tunis, Tunisia","correspondingAuthor":false,"prefix":"","firstName":"Wafa","middleName":"Rjiba","lastName":"Bahri","suffix":""},{"id":503260831,"identity":"400d3152-b985-4875-832d-1e3f7014feb0","order_by":4,"name":"Jamila Ben Souissi","email":"","orcid":"https://orcid.org/0000-0003-1761-4204","institution":"National Institute of Agronomy of Tunisia (INAT), University of Carthage, Tunis, Tunisia","correspondingAuthor":false,"prefix":"","firstName":"Jamila","middleName":"Ben","lastName":"Souissi","suffix":""},{"id":503260832,"identity":"39be3936-58ca-428f-b535-ccf80fa13a78","order_by":5,"name":"Marina Chiappi","email":"","orcid":"https://orcid.org/0000-0002-9401-2509","institution":"Department of Biological, Geological and Environmental Sciences (BIGEA), University of Bologna (UNIBO), Bologna, Italy","correspondingAuthor":false,"prefix":"","firstName":"Marina","middleName":"","lastName":"Chiappi","suffix":""},{"id":503260833,"identity":"68a6aee4-33c2-4751-9f1e-a2d7d17a7113","order_by":6,"name":"Gianluca Sarà","email":"","orcid":"","institution":"Department of Earth and Marine Science (DiSTeM), University of Palermo, Palermo, Italy","correspondingAuthor":false,"prefix":"","firstName":"Gianluca","middleName":"","lastName":"Sarà","suffix":""}],"badges":[],"createdAt":"2025-08-20 17:17:21","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7419650/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7419650/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89621482,"identity":"49035ba3-b4e2-411c-94e0-41da43863d21","added_by":"auto","created_at":"2025-08-22 04:13:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1903791,"visible":true,"origin":"","legend":"\u003cp\u003eMethod of thermal performance curve analysis to identify the thermal niche of each species and co-existence windows: (A) Thermal performance curves of \u003cem\u003eCallinectes sapidus \u003c/em\u003e(in red, from Marchessaux et al., 2022) and \u003cem\u003ePortunus segnis \u003c/em\u003e(in blue, from Marchessaux et al., 2024), and (B) Dominance index calculated to determine the temperature niches for each species to map the distribution of both species. The marginal effect of temperature on the response variable was modeled using a generalized additive model (GAM). The resulting curve reveals a non-linear relationship with temperature and the confidence intervals suggest a robust estimate in the densely sampled temperature ranges (Supplementary Figure 1).\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-7419650/v1/e349d02f22989e7a3c3e8bf4.png"},{"id":89621484,"identity":"3a1a5390-a86c-4315-a281-200b6aaee9bc","added_by":"auto","created_at":"2025-08-22 04:13:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2966523,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Distribution of the thermal habitats for \u003cem\u003eCallinectes sapidus, Portunus segnis \u003c/em\u003eand co-existence areas in the Mediterranean Sea, for the year 2023; (B) monthly evolution of the probability of presence of \u003cem\u003eC. sapidus \u003c/em\u003e(red), \u003cem\u003eP. segnis \u003c/em\u003e(blue)\u003cem\u003e, \u003c/em\u003eand co-occurrence (dark), in each Mediterranean country (on the right) for 2023.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-7419650/v1/868028d0a7a477354556a18c.png"},{"id":89621770,"identity":"7c0264cd-7e15-4cc9-a345-4e1609c788b9","added_by":"auto","created_at":"2025-08-22 04:21:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2994023,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Distribution of the thermal habitats for \u003cem\u003eCallinectes sapidus, Portunus segnis \u003c/em\u003eand co-existence areas in the Mediterranean Sea, for the year 2050; (B) monthly evolution of the probability of presence of \u003cem\u003eC. sapidus \u003c/em\u003e(red), \u003cem\u003eP. segnis \u003c/em\u003e(blue)\u003cem\u003e, \u003c/em\u003eand co-occurrence (dark), in each Mediterranean country (on the right) for 2050.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-7419650/v1/782ab52a25d5480d7378836a.png"},{"id":89621771,"identity":"de3089d0-955c-46d3-91c1-f5366ad7949d","added_by":"auto","created_at":"2025-08-22 04:21:41","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2810140,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Situation of blue crab species dominance and co-occurrence: changes in species dominance/co-occurrence between 2050 and 2023 scenarios for each Mediterranean country. Values are available in the Supplementary Table 1, (B) management recommendations regarding the different situations identified.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-7419650/v1/c57db144b0bef45f78ff7213.png"},{"id":89622880,"identity":"fe9f1d97-fc90-4609-893e-0d56241f69ca","added_by":"auto","created_at":"2025-08-22 04:45:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10104498,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7419650/v1/746cea7e-0d3e-424c-a9ad-2fd42d5c75fb.pdf"},{"id":89621483,"identity":"1f1e1eed-bc09-453f-9700-3dbbcda4c703","added_by":"auto","created_at":"2025-08-22 04:13:41","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":220222,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary material\u003c/p\u003e","description":"","filename":"Supplementary.docx","url":"https://assets-eu.researchsquare.com/files/rs-7419650/v1/51ae2fcbf0eb38a70365144e.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eFight club, or the story of the invasion of two marine blue crab species in the Mediterranean Sea\u003c/p\u003e","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe expansion of marine species results from climate change and human activities (Gallardo et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Ramos et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Seebens et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The global rise in ocean temperatures influences organism performance, population dynamics, and ecosystem structure (Yao \u0026amp; Somero \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), leading to a migration of species toward the poles and temperate zones in response to their adaptive capacity (Sar\u0026agrave; et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Changes in temperature regimes, surface currents, ice cover, and other essential processes promote both natural and anthropogenic species dispersal, allowing some species to survive and establish themselves in previously unsuitable areas (Hellmann et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Bellard et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Chan et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Occhipinti-Ambrogi \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Temperature plays a key role in biochemical and metabolic reactions, determining organisms\u0026rsquo; thermal tolerance limits, phenology, and distribution (Walter \u0026amp; Graf \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Helmuth \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Freitas et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Yao \u0026amp; Somero \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; DeLong et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Variations in environmental exposure explain the diversity of physiological responses observed, highlighting the importance of assessing the effects of climate change across all coastal systems (Cooley et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eMetabolism is a fundamental factor to consider in organisms, as it represents the sum of all potential biochemical work occurring within an organism (DeLong et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Metabolism governs vital functions throughout an organism's life, including growth, reproduction, maintenance, and activity (Kontopoulos et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), which, in turn, influence population dynamics and long-term sustainability. Metabolism is a universal function across all living organisms, from bacteria to whales, including photosynthetic organisms, and operates at every biological level (DeLong et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kontopoulos et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). One of the most common measures in metabolism studies is the assessment of thermal performance, particularly in ectothermic species\u0026mdash;organisms whose body temperature aligns with their environment. Ectotherms typically show an increase in metabolic rate as temperature rises, reaching a peak, referred to as the optimum, followed by a decline beyond this thermal optimum (Verberk et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Rezende \u0026amp; Bozinovic \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eUnderstanding the temperature dependence of metabolic rate requires analyzing thermal performance curves (TPCs), which capture peak metabolic rate (Rmax) (Angilletta Jr \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Molnar et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Angilletta \u0026amp; Angilletta \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). The decline in metabolic rate beyond the thermal optimum (Topt) may result from reduced enzymatic efficiency at higher temperatures. Metabolic performance is influenced by substrate delivery, enzyme kinetics, catalytic efficiency, and the structural integrity of oxidative phosphorylation sites (Angilletta \u0026amp; Angilletta \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). TPCs offer an integrated view of how organisms perform across temperature gradients. In the context of climate change, TPCs serve as key indicators of species\u0026rsquo; thermal fitness. Four main models\u0026mdash;\u0026ldquo;hotter is better,\u0026rdquo; \u0026ldquo;metabolic cold adaptation,\u0026rdquo; \u0026ldquo;colder is better,\u0026rdquo; and \u0026ldquo;peak matching\u0026rdquo;\u0026mdash;help predict species\u0026rsquo; responses to temperature change (DeLong et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Comparing TPCs allows assessment of species dominance or coexistence, and has proven useful for predicting invasive species\u0026rsquo; distributions and supporting early detection and management.\u003c/p\u003e\u003cp\u003eIn 2023, exceptional warming of Mediterranean waters (Wedler et al. 2023) facilitated the rapid expansion of the invasive American blue crab \u003cem\u003eCallinectes sapidus\u003c/em\u003e (Rathbun, 1896) into marine, brackish, and freshwater habitats across Mediterranean countries (Castriota et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Italy\u0026rsquo;s entire coastline was affected, while Tunisia saw expansion into the Gulf of Gab\u0026egrave;s (J. Ben Souissi, pers. obs.). The same year, the Red Sea swimming blue crab, \u003cem\u003ePortunus segnis\u003c/em\u003e (Forsk\u0026aring;l, 1775), native to the Indo-Pacific, was reported further North than ever before\u0026mdash;along Spain\u0026rsquo;s Gulf of Cadiz (de Carvalho-Souza et al. 2023) and the Italian Adriatic coast (Grati et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Until then, \u003cem\u003eP. segnis\u003c/em\u003e had been confined to the southeastern Mediterranean especially from Tunisia to Turkey.\u003c/p\u003e\u003cp\u003eThis northward shift suggests possible future co-existence of \u003cem\u003eP. segnis\u003c/em\u003e and \u003cem\u003eC. sapidus\u003c/em\u003e, which may intensify impacts on ecosystems and socio-economic sectors. We hypothesize that their co-existence could exacerbate socio-economic challenges, particularly for artisanal fisheries and shellfish farming, by increasing damage to gear and competition for resources. The primary objective of our study is therefore to assess the potential for thermal niche-driven co-existence between \u003cem\u003eP. segnis\u003c/em\u003e and \u003cem\u003eC. sapidus\u003c/em\u003e, and to develop predictive tools that can anticipate and map their co-occurrence. By doing so, we aim to identify priority areas for monitoring and inform proactive management strategies to mitigate the ecological and economic risks posed by these two invasive species under current and future climate scenarios.\u003c/p\u003e\u003cp\u003eThe present study aims to analyze the distribution of non-native species based on their TPCs and propose a tool to assess the species co-occurrence and dominance based on their metabolic responses to temperature. To do this, we used experimental measurements of metabolic performance of two invasive blue crab species and tested and verified whether temperature-induced metabolic differences influence species distribution, dominance and co-occurrence. Our research focuses on two invasive blue crab species from the Portunidae family in the Mediterranean: the Atlantic blue crab, \u003cem\u003eCallinectes sapidus\u003c/em\u003e, and the Red Sea blue crab, \u003cem\u003ePortunus segnis\u003c/em\u003e. While previous studies have examined their ecological impacts and spread, there is still a gap in understanding how their metabolic responses to temperature influence their distribution, co-occurrence, and competitive dynamics. By analyzing their thermal performance curves (TPCs) and developing a predictive tool, this study aims to bridge that gap and provide insights into the role of temperature-driven physiological traits in shaping invasive species interactions.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Thermal performance curve models\u003c/h2\u003e\u003cp\u003eTo evaluate co-occurrence and dominance scenarios between \u003cem\u003eCallinectes sapidus\u003c/em\u003e and \u003cem\u003ePortunus segnis\u003c/em\u003e, we analyzed their thermal performance curves (TPCs) from Marchessaux et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Both TPCs were plotted using the original curve equations and compared using the framework by DeLong et al. (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) (\u0026ldquo;hotter is better,\u0026rdquo; \u0026ldquo;cold adaptation,\u0026rdquo; etc.). We developed a dominance index (D), calculated as the difference between species' metabolic rates at each temperature. Negative D values indicate \u003cem\u003eC. sapidus\u003c/em\u003e dominance, positive values indicate \u003cem\u003eP. segnis\u003c/em\u003e dominance, and D\u0026thinsp;=\u0026thinsp;0 indicates co-occurrence. The D equation was applied to temperature layers to spatially map dominance and coexistence across the Mediterranean. To test model robustness, we used a generalized additive model (GAM) with spline smoothing via the \u003cb\u003egam()\u003c/b\u003e function in the \u003cb\u003emgcv\u003c/b\u003e package (Wood \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) in R Studio (v2024.12.0). We also used LOESS regression to assess the sensitivity of predictions to temperature bounds, visualizing outputs across a standardized temperature grid.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Mapping the current and future thermal suitability\u003c/h2\u003e\u003cp\u003eThe D index curve was applied to predict the distribution of \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e under current (2023) and future (2050) climate scenarios (RCP 4.5 and RCP 8.5; CMIP5 models, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://cds.climate.copernicus.eu/\u003c/span\u003e\u003cspan address=\"https://cds.climate.copernicus.eu/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). Dominance values were extracted monthly for 16 Mediterranean countries. Annual proportions of species dominance and co-occurrence were mapped using R Studio (v2024.12.0) and QGIS (v3.10.7). Pie charts displayed these proportions, and a map showing percentage change from 2023 to 2050 highlighted national conservation priorities for \u003cem\u003eC. sapidus\u003c/em\u003e, \u003cem\u003eP. segnis\u003c/em\u003e, and their co-occurrence.\u003c/p\u003e\u003c/div\u003e"},{"header":"3 Results","content":"\u003cp\u003eThe metabolic respiration rate of the two species varies with temperature (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). \u003cem\u003eCallinectes sapidus\u003c/em\u003e reaches its maximum metabolic rate at 23.91\u0026deg;C, while \u003cem\u003ePortunus segnis\u003c/em\u003e peaks at a higher temperature, 33.64\u0026deg;C, indicating better adaptation of \u003cem\u003eP. segnis\u003c/em\u003e to warmer environments. At temperatures below approximately 23\u0026deg;C, \u003cem\u003eC. sapidus\u003c/em\u003e has a metabolic advantage (red zone), but beyond this point, \u003cem\u003eP. segnis\u003c/em\u003e becomes dominant (blue zone), with an increasing metabolic gap at higher temperatures (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). This figure underscores the thermal differences in the physiological performance of the two species, reflecting their respective ecological. adaptations.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn 2023, \u003cem\u003eC. sapidus\u003c/em\u003e dominated most Mediterranean regions (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). It was especially prevalent in the Western Mediterranean (France, Morocco, Spain, Italy), while \u003cem\u003eP. segnis\u003c/em\u003e was more widespread in the Eastern Mediterranean (Greece, Turkey, Cyprus, Lebanon, Egypt, Tunisia). Co-occurrence was observed across the basin, with higher proportions in the Southeast (e.g., Egypt, Cyprus). Monthly trends (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) showed \u003cem\u003eC. sapidus\u003c/em\u003e present year-round, particularly from May to September in France. In contrast, \u003cem\u003eP. segnis\u003c/em\u003e was dominant from April to October in Italy and from March to August in Tunisia, with similar patterns in Israel, Cyprus, and Egypt.\u003c/p\u003e\u003cp\u003eProjections for 2050 under the RCP 8.5 scenario show shifting dominance patterns between \u003cem\u003eCallinectes sapidus\u003c/em\u003e and \u003cem\u003ePortunus segnis\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). \u003cem\u003eC. sapidus\u003c/em\u003e remains dominant in the Western Mediterranean (France, Spain, Italy), while \u003cem\u003eP. segnis\u003c/em\u003e expands into regions where it was less prevalent in 2023 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). In the Eastern Mediterranean (Greece, Turkey, Cyprus), \u003cem\u003eP. segnis\u003c/em\u003e remains prevalent but with increased co-occurrence with \u003cem\u003eC. sapidus\u003c/em\u003e, suggesting west-to-east range expansion. Co-occurrence becomes more widespread (e.g., Algeria, Tunisia, Egypt), indicating overlapping habitats due to environmental shifts.\u003c/p\u003e\u003cp\u003eThe temporal evolution for 2050 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB) shows a shift in monthly presence probabilities toward later in the year. For example, in France, peak \u003cem\u003eC. sapidus\u003c/em\u003e presence may shift from May\u0026ndash;September (2023) to June\u0026ndash;October (2050). In Italy, \u003cem\u003eP. segnis\u003c/em\u003e\u0026rsquo; presence, initially April\u0026ndash;October, may extend to May\u0026ndash;November. Co-occurrence periods also shift rightward, occurring later in the year in countries like Turkey, Tunisia, Spain, and Greece. These changes reflect climate-driven shifts in species\u0026rsquo; phenology and potential increases in interspecific interactions, highlighting the need for updated management strategies in light of future overlap and competition between these invasive species.\u003c/p\u003e\u003cp\u003eThe percentage change between 2050 and 2023 highlights projected shifts in the distribution of \u003cem\u003eC. sapidus\u003c/em\u003e, \u003cem\u003eP. segnis\u003c/em\u003e, and their co-occurrence across the Mediterranean (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). In the Western Mediterranean, countries like France, Spain, and Italy are expected to see an increase in \u003cem\u003eC. sapidus\u003c/em\u003e, indicating range expansion or greater dominance. In contrast, Algeria, Tunisia, Libya, Egypt, and Israel show decreasing \u003cem\u003eC. sapidus\u003c/em\u003e and co-occurrence, but increasing \u003cem\u003eP. segnis\u003c/em\u003e, reflecting significant distributional changes. In the Eastern Mediterranean, Greece and Turkey are projected to experience a notable rise in \u003cem\u003eP. segnis\u003c/em\u003e, suggesting continued eastward expansion. Overall, these trends underscore the dynamic nature of species distribution in response to climate change and highlight the need for adaptive, country-specific management strategies. Management needs vary latitudinally. Southern Mediterranean countries (e.g., Morocco, Algeria, Tunisia, Libya, Egypt, Israel) should prioritize \u003cem\u003eP. segnis\u003c/em\u003e control. Similarly, Italy and Albania in the Adriatic Sea face growing \u003cem\u003eP. segnis\u003c/em\u003e pressure. Spain, Croatia, Montenegro, Turkey, and Lebanon should focus efforts on \u003cem\u003eC. sapidus\u003c/em\u003e. Greece and Cyprus, showing increases or persistent presence of both species, will require management strategies targeting both \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e to mitigate ecological and socio-economic impacts.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB, provides a detailed framework for managing the presence of two crab species, \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e, in the Mediterranean region, focusing on their individual and co-occurring distributions based on the changes identified between 2050 and 2023. For \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e, a decrease in their presence was not considered a priority for management efforts. However, an increase in \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e populations requires management intervention to mitigate potential ecological impacts. When both species co-occur, management is required to address the combined ecological and socio-economic impacts, emphasizing the need for integrated strategies to limit negative outcomes. 3 situations were identified:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eIf one of the two blue crab species was already present in a country, the recommended actions include monitoring blue crabs and quantifying their ecological impacts, implementing spatial control and fisheries management, and raising awareness about socio-ecological issues. It is the case for all Mediterranean countries, as \u003cem\u003eC. sapidus\u003c/em\u003e is currently widespread.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eFor countries where the species are not currently present, but are predicted to appear in the future, especially for \u003cem\u003eP. segnis\u003c/em\u003e, early detection and rapid response mechanisms are crucial to prevent establishment and spread. If no changes were identified between 2050 and 2023, overall, proactive and adaptive management strategies to address the dynamic distribution of these crab species, aiming to limit their co-occurrence and the associated socio-ecological impacts are crucial, as underscored by the figure.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eIf no change was identified between 2050 and 2023, i.e. the predicted presence of one or both blue crab species is the same in both scenarios, then management measures (situation 1) should be implemented on both species together.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eWorking on the metabolic values of species is essential to understanding their persistence and the possibility of coexistence between them. Metabolism, as a direct reflection of an organism's physiological functioning, conditions its performance, growth, reproduction and survival in a given environment (Brown et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). By comparing these values between species and as a function of temperature, it is possible to identify the most favorable environmental contexts to each. For example, some species perform better at higher temperatures, according to the \u0026ldquo;hotter is better\u0026rdquo; principle (Huey \u0026amp; Kingsolver \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; DeLong et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), while others may benefit from colder environments (\u0026ldquo;colder is better\u0026rdquo;) if they maintain metabolic efficiency at lower temperatures (Angilletta et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). These dynamics make it possible to predict not only under which conditions a species is likely to persist, but also whether two species can coexist or whether one is likely to exclude the other due to a competitive advantage linked to metabolism (Tilman \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Dell et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The study of metabolic values makes it possible to link individual physiological mechanisms to larger-scale ecological dynamics.\u003c/p\u003e\u003cp\u003eUnderstanding the coexistence of \u003cem\u003eCallinectes sapidus\u003c/em\u003e and \u003cem\u003ePortunus segnis\u003c/em\u003e is crucial for predicting the ecological consequences of biological invasions in the Mediterranean Sea. Historically occupying distinct thermal niches, these two invasive crabs now increasingly overlap due to climate change, especially during warmer months. Consistent with the \u0026ldquo;hotter is better\u0026rdquo; hypothesis (DeLong et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), P. \u003cem\u003esegnis\u003c/em\u003e, a tropical species, gains a competitive advantage under rising temperatures, potentially shifting species dominance in future scenarios. Both species are aggressive, opportunistic omnivores feeding on mollusks, crustaceans, and fish (Ryer \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Hosseini et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Mancinelli et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Chiesa et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Their growing overlap intensifies competition for food, disrupts trophic interactions, and threatens native biodiversity (Mancinelli et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Rabaoui et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Studies show they alter food webs and may engage in interspecific and intraguild cannibalism, increasing ecological pressures.\u003c/p\u003e\u003cp\u003eUsing species distribution models and thermal performance curves, we identified current and future coexistence hotspots. These tools provide early warning indicators to guide detection, monitoring, and management. Our findings highlight the need to incorporate physiological traits and temperature-driven dynamics into invasion frameworks to address long-term ecological and socio-economic impacts. \u003cem\u003ePortunus segnis\u003c/em\u003e\u0026rsquo; thermal advantage suggests a shift in competitive balance, challenging the assumption of stable coexistence. As both species increasingly impact fisheries\u0026mdash;damaging gear and reducing fish stocks (Ben Souissi et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u0026mdash;their expanding presence could further strain ecosystems and livelihoods. Understanding and predicting their interactions is essential for effective policy and mitigation planning.\u003c/p\u003e\u003cp\u003eThe \u003cem\u003e\"multiple species invasion\"\u003c/em\u003e hypothesis supports the idea that the effects of co-occurring non-indigenous species (NIS) on local communities may be greater, lesser, or negligible compared to the impact of each species in isolation, as demonstrated in plants (Kuebbing et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Thus, a range of possible outcomes may arise from the interaction between these two blue crabs, from a facilitative cumulative scenario\u0026mdash;commonly referred to as \u003cem\u003e\"invasion meltdown\"\u003c/em\u003e where one species enhances the success of the other (Berglund et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) \u0026mdash; to a scenario where their effects remain independent, with minimal interaction between them (Rauschert \u0026amp; Shea \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Previous studies suggest that the impact of two co-occurring NIS largely depends on the degree of their ecological niches overlap, reflected in their functional, life-history, and ecological traits (Ricciardi et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Blackburn et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Sheppard et al. (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) suggested that the greater the similarity between two co-occurring alien species, the higher the invasion success of both, which may amplify their detrimental effects on local communities (Berglund et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Furthermore, anthropogenic environmental changes may intensify these impacts by introducing new pathways for invasion (Sar\u0026agrave; et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Sheppard et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In the Mediterranean, evidence suggests that the occurrence and population densities of invasive species are driven by rising temperature and the absence of natural competitors and predators (Raitsos et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Hoffman \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Elliott et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Our findings reinforce these observations, highlighting the role of climate change in shaping species interactions and invasion dynamics.\u003c/p\u003e\u003cp\u003eThe main outcome of the study of the coexistence of invasive blue crabs involved generating maps, cost-effective tools providing robust visualizations for early detection (useful for Early Detection and Rapid Response - EDRR - programs; (Harvey \u0026amp; Mazzotti \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). These maps enable exploration of the potential geographic distribution of the two species and their overlapping areas, informing risk management plans (Tulloch et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). To facilitate stakeholder and manager understanding, a \u0026ldquo;cohabitation index\u0026rdquo; (Elleouet et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) was developed to infer blue crab hotspots based on distribution overlap. Additionally, to enhance EDRRs addressing \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e, species distribution models (SDMs) were implemented using IPCC AR5 climate change scenarios (RCP 4.5 and RCP 8.5) to predict future occurrences of the two species up to 2050. This step provides a robust foundation for future conservation planning, helping predict effective multispecies management decisions and contributing valuable insights into community assembly (Sheppard et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eKnowledge of thermal limits is also valuable for selecting effective biocontrol agents and guiding community-based monitoring efforts through citizen science campaigns (Reaser et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). This information informs policy decisions, such as establishing quarantine zones or regulating the movement of goods between regions with differing thermal profiles (Venette et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). This current study offers critical information for developing targeted and sustainable management strategies to address invasions of \u003cem\u003eC. sapidus\u003c/em\u003e and \u003cem\u003eP. segnis\u003c/em\u003e. Based on the international recommendations for the management of both invasive blue crabs in the Mediterranean Sea (UNEP/MAP-SPA/RAC \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) and by identifying coexistence zones and analyzing their distribution under different climate scenarios (RCP 4.5 and RCP 8.5), it becomes possible to prioritize control efforts in regions with the greatest ecological and socio-economic impact:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eOne of the blue crab species is dominant or only present in the national territory\u003c/b\u003e: Decision-makers can therefore use the results obtained in our study to implement measures to control the species on a national level. In this case, prediction maps for current and future scenarios enable decision-makers to determine the areas where the species could expand (Marchessaux et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Using predictive maps, decision-makers could, for example, set up early species detection programs (EDRR) using citizen science, or regular monitoring of potential risk areas. Monitoring and anticipating the introduction of species on a national scale also requires precise, anticipatory regulations.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eCo-occurrence is identified in the national territory\u003c/b\u003e: regions where both species coexist could be targeted for intensive fishing measures to simultaneously reduce their densities (Azzurro et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Additionally, understanding their habitat preferences and seasonal activity periods enables the design of species-specific traps or selective capture techniques to minimize bycatch of native species. To do that we need to develop acoustic telemetry to determine how the two species will interact and how they use the space in terms of habitats preferences, temperature referendum, and food availability. Insights into combined ecological impacts, such as resource competition and disruptions to trophic networks, can guide habitat restoration programs to bolster populations of resilient native species.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eUnderstanding this co-occurrence is crucial for identifying potential ecological and competitive mechanisms, particularly in shared environments. The study of ecological niche overlap between two invasive species is crucial for understanding and managing ecosystems. First, it allows for the evaluation of potential interactions between these species, thereby anticipating consequences for local biodiversity. By identifying areas of niche overlap, managers can target control efforts more effectively. This knowledge is critical for developing conservation and restoration strategies aimed at maintaining ecological balance and enhancing ecosystem resilience in the face of biological invasions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflict of interest\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthors Contributions\u003c/h2\u003e\u003cp\u003eG.M. conceived the ideas and hypotheses. G.M. analyzed the data with assistance from V.G., and M.C. for the management part; G.M. wrote the first version of the manuscript. The manuscript was edited, revised and approved by all authors.\u003c/p\u003e\u003ch2\u003eData availability statement\u003c/h2\u003e\u003cp\u003eThe data that support the findings of this study are available from the literature for the Thermal Performance Curve (Marchessaux et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e (\u003cem\u003eC. sapidus)\u003c/em\u003e, Marchessaux et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e (\u003cem\u003eP. segnis\u003c/em\u003e)), and the percentage and maps by contacting the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAngilletta Jr, M.J. (2006). Estimating and comparing thermal performance curves. \u003cem\u003eJ. Therm. Biol.\u003c/em\u003e, 31, 541\u0026ndash;545.\u003c/li\u003e\n\u003cli\u003eAngilletta, M.J. \u0026amp; Angilletta, M.J. (2009). 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Bull.\u003c/em\u003e, 59, 468\u0026ndash;479.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Aix-Marseille Université","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Callinectes sapidus, Portunus segnis, Invasive species management, Climate change","lastPublishedDoi":"10.21203/rs.3.rs-7419650/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7419650/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eClimate change and anthropogenic pressures are driving the expansion of marine species, influencing organism performance, population dynamics, and ecosystem structure. In the Mediterranean Sea, the invasive American blue crab, \u003cem\u003eCallinectes sapidus\u003c/em\u003e, and the Red Sea blue crab, \u003cem\u003ePortunus segnis\u003c/em\u003e, are expanding their ranges in response to accelerated ocean warming. This study analyzes their Thermal Performance curves (TPCs) to predict co-occurrence and dominance under climate scenarios. \u003cem\u003eCallinectes sapidus\u003c/em\u003e thrives in cooler temperatures, while \u003cem\u003eP. segnis\u003c/em\u003e is better adapted to warmer environments. These patterns indicate a latitudinal partitioning driven by temperature tolerance, with only limited temporal overlap during the warmest months. Notably, while coexistence in 2023 was rare and spatially restricted, by 2050 these zones become more extensive and frequent, especially from July through October, indicating a future rise in interspecific interactions. These future projections indicate that rising temperatures will favor \u003cem\u003eP. segnis\u003c/em\u003e, increasing competition and co-occurrence with \u003cem\u003eC. sapidus\u003c/em\u003e, particularly in summer. The study highlights the importance of understanding temperature-driven physiological traits in shaping invasive species interactions and developing tools for management. Maps generated from TPCs and thermal dominance indices inform risk management plans and conservation efforts, helping to mitigate the ecological and socio-economic impacts of these invasive species.\u003c/p\u003e","manuscriptTitle":"Fight club, or the story of the invasion of two marine blue crab species in the Mediterranean Sea","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-22 04:13:36","doi":"10.21203/rs.3.rs-7419650/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"03b9d053-8970-4090-b36d-b4de89830e3f","owner":[],"postedDate":"August 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":53541304,"name":"Animal Physiology"},{"id":53541305,"name":"Marine and Freshwater Ecology"},{"id":53541306,"name":"Conservation Biology"}],"tags":[],"updatedAt":"2025-08-22T04:13:36+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-22 04:13:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7419650","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7419650","identity":"rs-7419650","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}