{"title":"Ocean Acidification Impairs the Chiton Shadow Defensive Response via Degradation of Aragonitic Lenses","authors":"Ryo Matsumoto, Naoto Takiyama, Koetsu Kon","doi":"10.1111/maec.70123","DOIUrl":"https://doi.org/10.1111/maec.70123","url":null,"abstract":"<p>Ocean acidification (OA) has the potential to disrupt the behavior of marine organisms by altering the function of γ-aminobutyric acid type A (GABA<sub>A</sub>) receptors. In addition, OA can impair sensory performance by reducing the calcification of mineralized sensory structures. Some species of polyplacophoran mollusks (chitons) possess calcified visual organs (aragonitic lenses) that contribute to shadow defense responses triggered by sudden decreases in overhead illumination. Therefore, we hypothesized that OA affects this response by impairing GABA<sub>A</sub>-mediated signaling or lens calcification. To test this hypothesis, we exposed chitons to “control” or acidified seawater and examined their shadow defensive behavior with and without gabazine, a GABA<sub>A</sub> antagonist known to restore OA-induced GABAergic dysfunction. Although gabazine did not eliminate behavioral differences between the control and acidified groups, acidification reduced the response strength, suggesting that factors other than GABA<sub>A</sub>-mediated signaling may contribute to the observed behavioral impairment. Microscopic observations revealed clouding of aragonitic lenses under acidic conditions, suggesting reduced optical performance. Overall, our results indicate that OA-induced degradation of calcified lens structures is associated with impaired shadow defense responses and may contribute to behavioral dysfunction. To the best of our knowledge, this study provides the first evidence that acidification-induced physical and optical changes in the visual anatomy can alter behavioral performance in animals.</p>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maec.70123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shaye Ogurek, William D. Halliday, Mica R. X. Smith, Matthew K. Pine, Nick Brown, Aneesh P. H. Bose, Sigal Balshine, Francis Juanes
{"title":"Temporal and Tidal Rhythms Shape Courtship and Agonistic Calls in Plainfin Midshipman Toadfish","authors":"Shaye Ogurek, William D. Halliday, Mica R. X. Smith, Matthew K. Pine, Nick Brown, Aneesh P. H. Bose, Sigal Balshine, Francis Juanes","doi":"10.1111/maec.70120","DOIUrl":"https://doi.org/10.1111/maec.70120","url":null,"abstract":"<p>In many species, acoustic communication is essential for successful reproduction, parental care, and predator defense. The plainfin midshipman, <i>Porichthys notatus</i>, is a soniferous toadfish that relies on acoustic communication, with nest-guarding males emitting long, tonal “hums” to attract mates, and short “grunts” and “growls” to defend nests and offspring from competitors and predators in their intertidal breeding grounds. Although these three vocalizations are a critical part of this species' repertoire, we still know relatively little about how these fish modulate their vocal communication in the complex acoustic environment of the marine intertidal zone. In this study, we recorded plainfin midshipman vocalizations at two sites on Vancouver Island, British Columbia, Canada, in 2018 and 2020 to better understand how season and abiotic conditions influence the occurrence of hums, growls and grunts. Hum presence at both locations peaked in June, increased at night compared to daytime, and positively correlated with water depth (tidal height). Hums also fluctuated in accordance with the lunar cycle, with elevated call presence observed during the quarter moon and associated neap tide phases. Growls similarly varied with the lunar cycle, but less notably than hums while grunts did not clearly covary with the lunar cycle. Growls and grunts both increased with water depth and were produced at similar rates both during the day and night. Our study demonstrates that plainfin midshipman adjust their acoustic behavior to match natural environmental cycles, and that the lunar and tidal cycles are important factors affecting reproductive behavior in this vocal intertidal fish.</p>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maec.70120","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
André Pardal, Aline S. Martinez, Ronaldo A. Christofoletti
{"title":"Habitat Isolation Influences Population Structure of Intertidal Crustaceans and Molluscs on Boulder-Dominated Rocky Shores in SE Brazil","authors":"André Pardal, Aline S. Martinez, Ronaldo A. Christofoletti","doi":"10.1111/maec.70121","DOIUrl":"https://doi.org/10.1111/maec.70121","url":null,"abstract":"<p>On sheltered rocky shores in SE Brazil, variation in habitat configuration (non-isolated vs. isolated boulders) acts as a natural exclusion experiment on a key isopod consumer, leading to potential interspecific competitive release. The semiterrestrial grazing isopod <i>Ligia exotica</i> forages almost exclusively on non-isolated boulders, resulting in decreased biofilm biomass. Based on these divergent patterns, we tested whether the population structure of grazing gastropods and barnacles differs between non-isolated and isolated boulders. We hypothesised that (i) grazing gastropods exhibit greater size, biomass, and abundance on isolated boulders, due to higher biofilm availability or competitive release; and (ii) barnacle density differs between boulder types, potentially due to the contrasting influence of biofilm on larval settlement or the accidental removal of newly settled larvae. Confirming previous observations, foraging of the isopod <i>L. exotica</i> was intense on non-isolated boulders (1.58 isopods · min<sup><b>−</b>1</sup> · m<sup><b>−</b>2</sup>) and almost absent on isolated boulders (0.04 isopods · min<sup><b>−</b>1</sup> · m<sup><b>−</b>2</sup>). The density of grazing gastropods and barnacles varied between boulder types, with site-specific effects. As predicted, grazing gastropods were 19%–37% larger, and their total biomass was 88% greater on isolated boulders. These findings underscore the ecological importance of habitat configuration at small scales, suggesting that even subtle changes in connectivity can trigger bottom-up and top-down processes that propagate through food webs.</p>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maec.70121","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149047995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. A. Rubeena, Jenny A. Angarita-Báez, T. R. Athira, K. M. Aarif
{"title":"Responses of Benthic Macroinvertebrates to Long-Term Environmental Variability in Two Key Habitats Along the West Coast of India","authors":"K. A. Rubeena, Jenny A. Angarita-Báez, T. R. Athira, K. M. Aarif","doi":"10.1111/maec.70118","DOIUrl":"https://doi.org/10.1111/maec.70118","url":null,"abstract":"<div>\u0000 \u0000 <p>Benthic macroinvertebrates form the foundation of coastal wetland food webs and play a critical role in sustaining higher trophic levels, including wintering migrant shorebirds. However, long-term changes in major benthic prey groups and their environmental drivers remain poorly quantified in tropical coastal systems. In this study, we analysed a 14-year dataset (2010–2023) from two key adjacent microhabitats along the west coast of India to assess long-term trends in benthic macroinvertebrate abundance and to identify the key physicochemical factors regulating benthic dynamics. Benthic macroinvertebrates were sampled systematically alongside water-quality parameters and sediment properties, and benthic macroinvertebrate abundance was modelled using a negative binomial framework to account for overdispersed count data. Results reveal a persistent long-term decline in overall benthic prey abundance. Water chemistry and sediment properties emerged as important drivers, with increasing chlorophyll a, pH, salinity and water phosphate exerting strong negative effects on prey abundance. Negative relationships between sediment textural variables and prey abundance also suggest a possible influence of sediment composition on benthic prey groups. Taxon-specific responses showed differences in sensitivity to environmental variation, with polychaetes and bivalves showing pronounced sensitivity to environmental stress, while some crustaceans exhibited greater tolerance to altered conditions. These findings demonstrate that interacting physicochemical stressors are influencing the abundance of major benthic prey groups over decadal timescales, with important implications for coastal food webs and the trophic support of winter migrant shorebirds. The study underscores the value of long-term monitoring and process-based modelling for changes in benthic prey abundance and informing effective coastal wetland management.</p>\u0000 </div>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149047996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lindsey Noel Nelson, W. David McElroy, Giovanni Gianesin, Jason M. Morson, Anna J. M. Mercer
{"title":"Surficial Substrate Complexity of the Central Gulf of Maine as Observed Through Video Observation During a Fisheries Survey","authors":"Lindsey Noel Nelson, W. David McElroy, Giovanni Gianesin, Jason M. Morson, Anna J. M. Mercer","doi":"10.1111/maec.70119","DOIUrl":"https://doi.org/10.1111/maec.70119","url":null,"abstract":"<p>The Gulf of Maine is a geologically complex environment that supports a high diversity of plankton, invertebrates, and fish, including commercially important species. Its substrate heterogeneity is well known though existing high-resolution substrate data are limited, hindering effective fisheries management. This study utilized a video drop camera system to characterize surficial substrate during the NOAA Northeast Fisheries Science Center's Bottom Longline Survey from 2014 to 2021. Video footage was collected from 577 stations and proportional substrate presence was calculated. Principal Component Analysis (PCA) visualized similarities of substrate composition among stations, and five kriging interpolation methods were tested to predict PC scores across unsampled areas. Regression Kriging incorporating depth and the terrain ruggedness index provided the most detailed interpolations. Results confirmed the complex and heterogeneous nature of the Gulf of Maine seafloor, showing high proportions of gravel and cobble in shallower, rugose areas and high proportions of mud in deeper basins. This research offers an improved dataset and approach for ecosystem-based fisheries science, characterization of essential fish habitat, marine spatial planning, and complements existing broad-scale efforts for habitat association studies.</p>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maec.70119","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149047997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Contrasting Traits of Common Molluscan Species Across Sites With Different Distances From Nutrient Sources in a Patagonian Bay","authors":"L. Pigato, L. P. Storero, M. S. Avaca","doi":"10.1111/maec.70122","DOIUrl":"https://doi.org/10.1111/maec.70122","url":null,"abstract":"<div>\u0000 \u0000 <p>Nutrient enrichment is a known threat to coastal ecosystems, yet detecting its biological impacts remains challenging. This study evaluated the variation in population and individual traits of three mollusks, <i>Brachidontes rodriguezii</i>, <i>Bostrycapulus odites</i>, and <i>Buccinastrum deforme,</i> in a eutrophic bay (40°42′ - 40°50′ S/64°43′ - 65°07′ W, Patagonia, Argentina) during 2021, across sites that differed in their proximity to the main anthropogenic source of pollution. The small mussel <i>B. rodriguezii</i> exhibited lower densities but significantly increased individual traits (larger size, higher weight, better condition index, and relative thickness) in the site closest to the source of nutrient pollution. Moreover, <i>B. rodriguezii</i> showed significant differences in the length–weight relationship among sites, with individuals showing higher growth rates in the site closest to the source of nutrient pollution. These findings suggest that individual-level traits may reflect the benefits of increased food availability, even when population-level metrics such as density decline. In contrast, the slipper limpet <i>B. odites</i> exhibited no clear variation across sites, while the scavenger snail <i>B. deforme</i> was absent in the distant site and only showed slight individual differences in the site closest to the main source of pollution. Overall, our results highlight <i>B. rodriguezii</i> as a promising candidate for monitoring nutrient-driven changes in these coastal benthic communities and emphasize the importance of species-specific traits in shaping mollusk variations to nutrient pollution.</p>\u0000 </div>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149047932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Effects of Turbidity on the Larval Survival of the Pelagic Shrimp Lucensosergia lucens in Suruga Bay, Japan","authors":"Kazuma Date, Tadashi Miyazaki, Haruka Shimotabira, Akira Matsumoto, Hisayuki Arakawa","doi":"10.1111/maec.70117","DOIUrl":"https://doi.org/10.1111/maec.70117","url":null,"abstract":"<p>In recent years, the pelagic shrimp <i>Lucensosergia lucens</i> population in Suruga Bay has declined drastically. One factor contributing to these declines is the influx of turbid river water into the inner bay, which serves as a spawning ground for pelagic shrimp. Here, we investigated the effects of particle concentration and particle size on pelagic shrimp larvae, as well as the vertical distribution of particles and larvae within inner Suruga Bay. The survival rate of pelagic shrimp larvae decreased as particle concentration increased, and this effect was particularly pronounced at a particle size of 100 μm for nauplius larva and 10 μm for elaphocaris larva. Particles in the inner bay were predominantly inorganic, with a modal size of 100–200 μm. Both the particle concentration in Fuji River water and the number of high-turbidity days have increased over time. These findings suggest that inorganic particles approximately 100 μm in size, entering from the river, may negatively affect the survival of pelagic shrimp larvae.</p>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maec.70117","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Samira Benslimane, Aziz Hafferssas, Mustapha Chaouadi
{"title":"First Record of the Non-Indigenous Copepod Acartia (Acanthacartia) tonsa Dana, 1849 and Its Spatio-Temporal Co-Occurrence With the Native Acartia (Acartiura) clausi Giesbrecht, 1889 Along an Anthropogenic Gradient on the Algerian Coast (South-Western Mediterranean Sea)","authors":"Samira Benslimane, Aziz Hafferssas, Mustapha Chaouadi","doi":"10.1111/maec.70115","DOIUrl":"https://doi.org/10.1111/maec.70115","url":null,"abstract":"<div>\u0000 \u0000 <p>Non-indigenous copepods are increasingly reported in the Mediterranean Sea, where anthropogenically disturbed coastal environments may facilitate their establishment and their co-occurrence with native congeners. This study provides the first record of the non-indigenous calanoid <i>Acartia tonsa</i> along the Algerian coast and examines its spatio-temporal distribution relative to the native <i>A. clausi</i>. Zooplankton was sampled during four seasonal campaigns covering a complete annual cycle at four coastal stations of Bordj El Kiffan (eastern Algiers Bay, 36°45′ N, 3°22′ E), arranged along an anthropogenic pressure gradient from a brine-discharge outlet to an offshore reference station. We hypothesised that (1) disturbed conditions generated by brine discharge and coastal enrichment favour the establishment of <i>A. tonsa</i>, and (2) as an early-stage invader, <i>A. tonsa</i> currently co-occurs with <i>A. clausi</i> with a high degree of niche overlap rather than excluding it. <i>A. tonsa</i> was recorded at all stations and seasons (4.80–5280 adults m<sup>−3</sup>), with a marked summer maximum, and consistently reached higher abundances than <i>A. clausi</i> (5.60–371.20 adults m<sup>−3</sup>). Both species peaked in summer and were positively associated with temperature, and niche-overlap indices remained high throughout the annual cycle, indicating spatial and temporal co-occurrence rather than exclusion. The relative abundance of the two congeners decreased from the enriched nearshore stations towards the offshore reference station, linking the dominance of <i>A. tonsa</i> to the local anthropogenic gradient.</p>\u0000 </div>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pallavi P. Choudhari, Siva Kiran Kumar Busala, Dokala Bhaskara Rao, Sai Elangovan S, Kiran Kumar Reddy Shiligireddy, C. K. Sherin, Buda Bikram Reddy, Prachi Marathe, Swarnaprava Behera, Naroju Veera Harikrishnachari, Eldhose Cheriyan, Garuda Vasudeva Madhu Gupta
{"title":"Comparative Responses of Coastal Arabian Sea Plankton to Different Ocean Acidification Simulation Methods","authors":"Pallavi P. Choudhari, Siva Kiran Kumar Busala, Dokala Bhaskara Rao, Sai Elangovan S, Kiran Kumar Reddy Shiligireddy, C. K. Sherin, Buda Bikram Reddy, Prachi Marathe, Swarnaprava Behera, Naroju Veera Harikrishnachari, Eldhose Cheriyan, Garuda Vasudeva Madhu Gupta","doi":"10.1111/maec.70113","DOIUrl":"https://doi.org/10.1111/maec.70113","url":null,"abstract":"<div>\u0000 \u0000 <p>Ocean acidification (OA) is expected to alter marine phytoplankton communities by modifying seawater carbonate chemistry, with important implications for marine food webs and biogeochemical cycling. In this study, we tested the hypothesis that comparable pH reductions achieved through different acidification methods generate distinct carbonate chemistry conditions and consequently different biological responses. A 5-day microcosm experiment was conducted using natural phytoplankton assemblages collected from the coastal Eastern Arabian Sea. OA was simulated by HCl addition (acid), CO<sub>2</sub> enrichment (CO<sub>2</sub>), and acid–base manipulation. Changes in carbonate chemistry, nutrients, phytoplankton community composition, pigments, bacteria, microzooplankton, and organic carbon pools were monitored. As expected, the three manipulation methods produced significantly different carbonate chemistry conditions despite comparable pH reductions. Repeated-measures ANOVA and Tukey's post hoc analyses confirmed significant treatment effects for pH, pCO<sub>2</sub>, DIC, HCO<sub>3</sub><sup>−</sup>, CO<sub>3</sub><sup>2−</sup>, and total alkalinity. By Day 5, CO<sub>2</sub> enrichment significantly increased total phytoplankton abundance and promoted microplankton dominance, driven by bloom-like proliferation of <i>Thalassiosira</i> sp., whereas picoplankton declined significantly. Conversely, pennate diatoms, cyanobacteria, dinoflagellates, and coccolithophores exhibited weak or negative responses. Concurrent changes in phosphate, nitrite, autotrophic bacteria, and microzooplankton indicated that nutrient availability, microbial recycling, and grazing interacted with carbonate chemistry to regulate phytoplankton succession. Our findings demonstrate that phytoplankton responses in the oligotrophic Eastern Arabian Sea are governed by the combined effects of carbonate chemistry, nutrient dynamics, and ecological interactions rather than pH alone.</p>\u0000 </div>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Hybridization Patterns Reveal Spatial Variation in Reproductive Isolation Between Two Closely Related Abalone Species","authors":"Shotaro Hirase, Wataru Nagase, Motoyuki Hara, Hideki Hamaoka, Naoki Itoh, Kiyoshi Kikuchi","doi":"10.1111/maec.70111","DOIUrl":"https://doi.org/10.1111/maec.70111","url":null,"abstract":"<p>Empirical studies demonstrating ecological speciation in marine invertebrates are limited. Two large abalone species—<i>Haliotis discus discus</i> and <i>H. madaka</i>—in the Japanese archipelago are considered to be involved in this process. Previous population genomic studies have indicated that hybridization between these two species continues because of incomplete reproductive isolation. However, owing to the limited number of samples in the previous study, the nature of hybridization remains unclear. In this study, we performed population genomic analyses of these two species using samples from multiple geographical regions. Analysis of 122 species-diagnostic single-nucleotide polymorphism loci revealed that observed heterozygosity was significantly higher in the <i>H. madaka</i> population than that in the <i>H. discus discus</i> population. ADMIXTURE analyses revealed biased introgression from <i>H. discus discus</i> into <i>H. madaka</i> populations, with the extent of introgression varying among regions. Most individuals with genomic introgression were classified as backcrosses, with no individuals demonstrating patterns consistent with F1 hybrids, indicating a bimodal hybrid zone. These findings suggest that selection may act against early-generation hybrids and that ecological speciation proceeds under geographically variable selective pressures in marine environments.</p>","PeriodicalId":49883,"journal":{"name":"Marine Ecology-An Evolutionary Perspective","volume":"47 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maec.70111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}