An integrated framework to identify and characterize regional-scale insect dispersal Felipe Dargent, Megan S. Reich, Marrissa Miller, Kala Studens, Nilofar Benvidi, et al. Ecological Applications, 2026 Forest pest insects cause major socio‐economic impacts, global losses of millions of dollars, and ecosystem changes. A key challenge for their management is tracing regional dispersal events critical to outbreak dynamics. We developed an integrated tracing framework for pest insects by combining isotope geolocation, ecological data, and atmospheric modeling, and applied this framework to the eastern spruce budworm moth ( Choristoneura fumiferana ), the most severe defoliator of the North American boreal forest, to trace outbreak dispersal events. We first generated a North American model of bioavailable sulfur isotope (δ 34 S) variation in space (isoscape) and then calibrated it to spruce budworm tissues of known origin. We then used an automated trap network with high temporal resolution to collect samples and identify potential immigration events of eastern spruce budworm to Nova Scotia, Canada. Finally, we traced the natal origin of these immigrants by sequentially integrating high‐probability regions of origin derived from δ 34 S values and estimated migration routes derived from biologically constrained atmospheric transport models. We find that this integrated framework allows us to narrow down the region of pest origins, restricting it to a few possible locations and demonstrating long‐distance dispersal of spruce budworm across ~400 km over the Gulf of St. Lawrence, Quebec. Our framework demonstrates that combining isotopic data with ecological indicators and atmospheric transport modeling offers improved resolution and understanding of insect dispersal ecology. This approach is transferable to trace other migratory insect species to address conservation, agriculture, and bio‐surveillance needs in the context of global environmental change.
Isotope geolocation and population genomics in Vanessa cardui: Short- and long-distance migrants are genetically undifferentiated Megan S Reich, Daria Shipilina, Venkat Talla, Farid Bahleman, Khadim Kébé, et al. Pnas Nexus, 2025 The painted lady butterfly Vanessa cardui is renowned for its virtually cosmopolitan distribution and the remarkable long-distance migrations as part of its annual, multigenerational migratory cycle. In winter, V. cardui individuals inhabit breeding grounds north and south of the Sahara, suggesting distinct migratory behaviors within the species as individuals migrate southward from Europe in the autumn. However, the evolutionary and ecological factors shaping these differences in migratory behavior remain largely unexplored. Here, we performed whole-genome resequencing and analyzed the hydrogen and strontium isotopes of 40 V. cardui individuals simultaneously collected in the autumn from regions both north and south of the Sahara. Our investigation revealed two main migratory groups: (i) short-distance migrants, journeying from temperate Europe to the circum-Mediterranean region and (ii) long-distance migrants, originating from Europe, crossing the Mediterranean Sea and Sahara, and reaching West Africa, covering up to over 4,000 km. Despite these stark differences in migration distance, a genome-wide analysis revealed that short- and long-distance migrants belong to a single intercontinental panmictic population extending from northern Europe to sub-Saharan Africa. Contrary to common biogeographic patterns, the Sahara is not a catalyst for population structuring in this species. No significant genetic differentiation or signs of adaptation and selection were observed between the two migratory phenotypes. Nonetheless, two individuals, who were early arrivals to West Africa covering longer migration distances, exhibited some genetic differentiation. The lack of genetic structure between short- and long-distance migrants suggests that migration distance in V. cardui is a plastic response to environmental conditions.
An ensemble machine learning bioavailable strontium isoscape for Eastern Canada Mael Le Corre, Felipe Dargent, Vaughan Grimes, Joshua Wright, Steeve D. Côté, et al. Facets, 2025 Bioavailable strontium isotope ratios (87Sr/86Sr) distribution across the landscape mainly follow the underlying lithology, making 87Sr/86Sr baseline maps (isoscapes) powerful tools for provenance studies. 87Sr/86Sr has already been used in Eastern Canada (EC) to track food and human remains origins, or to reconstruct animal mobility. While bioavailable 87Sr/86Sr isoscapes for EC can be extrapolated from global datasets using random forest modelling (RF), no regionally calibrated isoscape exists. Here, we produce a regionally calibrated bioavailable 87Sr/86Sr isoscape by analysing plants collected at 136 sites across EC, incorporating updated geological variables and applying a novel ensemble machine learning (EML) framework. We generated and compared isoscapes generated by the traditional RF and the EML approaches. Adding local bioavailable 87Sr/86Sr to a global dataset significantly improved the model prediction with a drastic increase of predicted 87Sr/86Sr and increased spatial uncertainty in the northern Canadian craton. EML produced similar 87Sr/86Sr predictions but with tighter spatial uncertainty distribution. Regionally calibrated RF and EML isoscapes significantly outperformed the global bioavailable RF isoscape, confirming the requirement for collecting local data in data-poor regions. This isoscape provides a baseline in EC to monitor and manage the movements and provenance of agricultural products, natural resources, endangered/harmful migratory species, and archaeological human remains and artifacts.
A trans-oceanic flight of over 4,200 km by painted lady butterflies Tomasz Suchan, Clément P. Bataille, Megan S. Reich, Eric Toro-Delgado, Roger Vila, et al. Nature Communications, 2024 The extent of aerial flows of insects circulating around the planet and their impact on ecosystems and biogeography remain enigmatic because of methodological challenges. Here we report a transatlantic crossing by Vanessa cardui butterflies spanning at least 4200 km, from West Africa to South America (French Guiana) and lasting between 5 and 8 days. Even more, we infer a likely natal origin for these individuals in Western Europe, and the journey Europe-Africa-South America could expand to 7000 km or more. This discovery was possible through an integrative approach, including coastal field surveys, wind trajectory modelling, genomics, pollen metabarcoding, ecological niche modelling, and multi-isotope geolocation of natal origins. The overall journey, which was energetically feasible only if assisted by winds, is among the longest documented for individual insects, and potentially the first verified transatlantic crossing. Our findings suggest that we may be underestimating transoceanic dispersal in insects and highlight the importance of aerial highways connecting continents by trade winds.
A hydrogen isoscape for tracing the migration of herbivorous lepidopterans across the Afro-Palearctic range Sana Ghouri, Megan S. Reich, Roger Lopez‐Mañas, Gerard Talavera, Gabriel J. Bowen, et al. Rapid Communications in Mass Spectrometry, 2024 Rationale Many insect species undertake multigenerational migrations in the Afro‐tropical and Palearctic ranges, and understanding their migratory connectivity remains challenging due to their small size, short life span and large population sizes. Hydrogen isotopes ( δ 2 H) can be used to reconstruct the movement of dispersing or migrating insects, but applying δ 2 H for provenance requires a robust isotope baseline map (i.e. isoscape) for the Afro‐Palearctic. Methods We analyzed the δ 2 H in the wings ( δ 2 H wing ) of 142 resident butterflies from 56 sites across the Afro‐Palearctic. The δ 2 H wing values were compared to the predicted local growing‐season precipitation δ 2 H values ( δ 2 H GSP ) using a linear regression model to develop an insect wing δ 2 H isoscape. We used multivariate linear mixed models and high‐resolution and time‐specific remote sensing climate and environmental data to explore the controls of the residual δ 2 H wing variability. Results A strong linear relationship was found between δ 2 H wing and δ 2 H GSP values ( r 2 = 0.53). The resulting isoscape showed strong patterns across the Palearctic but limited variation and high uncertainty for the Afro‐tropics. Positive residuals of this relationship were correlated with dry conditions for the month preceding sampling whereas negative residuals were correlated with more wet days for the month preceding sampling. High intra‐site δ 2 H wing variance was associated with lower relative humidity for the month preceding sampling and higher elevation. Conclusion The δ 2 H wing isoscape is applicable for tracing herbivorous lepidopteran insects that migrate across the Afro‐Palearctic range but has limited geolocation potential in the Afro‐tropics. The spatial analysis of uncertainty using high‐resolution climatic data demonstrated that many African regions with highly variable evaporation rates and relative humidity have δ 2 H wing values that are less related to δ 2 H GSP values. Increasing geolocation precision will require new modeling approaches using more time‐specific environmental data and/or independent geolocation tools.
The Afrotropical breeding grounds of the Palearctic-African migratory painted lady butterflies (Vanessa cardui) Gerard Talavera, Aurora García-Berro, Valery N. K. Talla, Ivy Ng’iru, Farid Bahleman, et al. Proceedings of the National Academy of Sciences of the United States of America, 2023 Migratory insects are key players in ecosystem functioning and services, but their spatiotemporal distributions are typically poorly known. Ecological niche modeling (ENM) may be used to predict species seasonal distributions, but the resulting hypotheses should eventually be validated by field data. The painted lady butterfly (Vanessa cardui) performs multigenerational migrations between Europe and Africa and has become a model species for insect movement ecology. While the annual migration cycle of this species is well understood for Europe and northernmost Africa, it is still unknown where most individuals spend the winter. Through ENM, we previously predicted suitable breeding grounds in the subhumid regions near the tropics between November and February. In this work, we assess the suitability of these predictions through i) extensive field surveys and ii) two-year monitoring in six countries: a large-scale monitoring scheme to study butterfly migration in Africa. We document new breeding locations, year-round phenological information, and hostplant use. Field observations were nearly always predicted with high probability by the previous ENM, and monitoring demonstrated the influence of the precipitation seasonality regime on migratory phenology. Using the updated dataset, we built a refined ENM for the Palearctic-African range ofV. cardui. We confirm the relevance of the Afrotropical region and document the missing natural history pieces of the longest migratory cycle described in butterflies.
Temporal stability of δ2H in insect tissues: Implications for isotope-based geographic assignments Eve E. Lindroos, Clément P. Bataille, Peter W. Holder, Gerard Talavera, Megan S. Reich Frontiers in Ecology and Evolution, 2023 Hydrogen isotope geolocation of insects is based on the assumption that the chitin in the wings of adult migratory insects preserves the hydrogen isotope composition (δ2H) of the larval stages without influence of adult diet. Here, we test this assumption by conducting laboratory feeding experiments for monarch butterflies (Danaus plexippus) including: (1) a starvation treatment where adults were not fed and (2) an enriched treatment where adults were fed a diet isotopically enriched in deuterium (~ +78‰) compared to the larval diet. The δ2H values of adult wings were measured at different time steps along the 24-day experiment. We also investigated intra-wing differences in δ2H values caused by wing pigmentation, absence of wing scales, and presence of major wing veins. We conclude that, although the magnitude of the changes in δ2H values are small (~6‰), wing δ2H values vary based on adult diet and insect age, particularly early after eclosion (i.e., 1–4 days). We found that wing shade, wing pigmentation, and the presence of wing scales do not alter wing δ2H values. However, wing samples containing veins had systematically higher δ2H values (~9‰), suggesting that adult diet influences the hemolymph that circulates in the wing veins. We hypothesise that there is a stronger influence of adult diet on the isotope signal of wings during early adult life relative to later life because of increased metabolic and physiologic activity in young insect wings. We argue that the influence of the isotopic contribution of adult diet is generally small and is likely minimal if the wings are carefully sampled to avoid veins. However, we also demonstrated that wings are not inert tissues, and that adult feeding contributes to some of the intra-population δ2H variance. We conclude that δ2H geolocation using insect wings remains valid, but that adult feeding, butterfly age and wing vein sampling generate an inherent uncertainty limiting the precision of geolocation.
Comprehensive analysis of the elemental composition and isotope ratios of honeys from US East Coast ÁZ Ragyák, T Varga, NAK Ahmed, M Braun, A Horváth, Z Lisztes-Szabó, ... Food Chemistry, 149254 , 2026 2026
An integrated framework to identify and characterize regional‐scale insect dispersal F Dargent, MS Reich, M Miller, K Studens, N Benvidi, K Perrault, ... Ecological Applications 36 (3), e70230 , 2026 2026
An ensemble machine learning bioavailable strontium isoscape for Eastern Canada M Le Corre, F Dargent, V Grimes, J Wright, SD Côté, MS Reich, ... Facets 10, 1-17 , 2025 2025 Citations: 11
Isotope geolocation and population genomics in Vanessa cardui: Short- and long-distance migrants are genetically undifferentiated MS Reich, D Shipilina, V Talla, F Bahleman, K Kébé, JL Berger, ... PNAS nexus 4 (2), pgae586 , 2025 2025 Citations: 15
Trans-Saharan migratory patterns in Vanessa cardui and evidence for a southward leapfrog migration MS Reich, S Ghouri, S Zabudsky, L Hu, M Le Corre, I Ng’iru, D Benyamini, ... iScience 27 (12) , 2024 2024 Citations: 13
A trans-oceanic flight of over 4,200 km by painted lady butterflies T Suchan, CP Bataille, MS Reich, E Toro-Delgado, R Vila, NE Pierce, ... Nature Communications 15 (1), 5205 , 2024 2024 Citations: 37
Pollen metabarcoding reveals the origin and multigenerational migratory pathway of an intercontinental-scale butterfly outbreak JL Gorki, R López-Mañas, L Sáez, M Menchetti, N Shapoval, A Andersen, ... Current Biology 34 (12), 2684-2692. e6 , 2024 2024 Citations: 15
A hydrogen isoscape for tracing the migration of herbivorous lepidopterans across the Afro‐Palearctic range S Ghouri, MS Reich, R Lopez‐Mañas, G Talavera, GJ Bowen, R Vila, ... Rapid Communications in Mass Spectrometry 38 (3), e9675 , 2024 2024 Citations: 7
Advancements in Isotopic Geolocation Tools for Insect Migration Research M Reich Université d'Ottawa/University of Ottawa , 2024 2024 Citations: 2
The Afrotropical breeding grounds of the Palearctic-African migratory painted lady butterflies ( Vanessa cardui ) G Talavera, A García-Berro, VNK Talla, I Ng’iru, F Bahleman, K Kébé, ... Proceedings of the National Academy of Sciences 120 (16), e2218280120 , 2023 2023 Citations: 26
Metals and metal isotopes incorporation in insect wings: Implications for geolocation and pollution exposure MS Reich, M Kindra, F Dargent, L Hu, DT Flockhart, DR Norris, ... Frontiers in Ecology and Evolution , 2023 2023 Citations: 17
Characterizing eastern spruce budworm’s large-scale dispersal events through flight behavior and stable isotope analyses F Dargent, JN Candau, K Studens, KH Perrault, MS Reich, CP Bataille Frontiers in Ecology and Evolution , 2023 2023 Citations: 11
Temporal stability of δ²H in insect tissues: Implications for isotope-based geographic assignments EE Lindroos, CP Bataille, PW Holder, G Talavera, MS Reich Frontiers in Ecology and Evolution 11, 45 , 2023 2023 Citations: 13
Erratic spatiotemporal vegetation growth anomalies drive population outbreaks in a trans-Saharan insect migrant R López-Mañas, JP Pascual-Díaz, A García-Berro, F Bahleman, ... Proceedings of the National Academy of Sciences 119 (19), e2121249119 , 2022 2022 Citations: 15
Continuous‐surface geographic assignment of migratory animals using strontium isotopes: A case study with monarch butterflies MS Reich, DTT Flockhart, DR Norris, L Hu, CP Bataille Methods in Ecology and Evolution 12 (12), 2445-2457 , 2021 2021 Citations: 55
Drought alters the trophic role of an opportunistic generalist in an aquatic ecosystem SL Amundrud, SA Clay-Smith, BL Flynn, KE Higgins, MS Reich, ... Oecologia 189 (3), 733-744 , 2019 2019 Citations: 17
MOST CITED SCHOLAR PUBLICATIONS
Continuous‐surface geographic assignment of migratory animals using strontium isotopes: A case study with monarch butterflies MS Reich, DTT Flockhart, DR Norris, L Hu, CP Bataille Methods in Ecology and Evolution 12 (12), 2445-2457 , 2021 2021 Citations: 55
A trans-oceanic flight of over 4,200 km by painted lady butterflies T Suchan, CP Bataille, MS Reich, E Toro-Delgado, R Vila, NE Pierce, ... Nature Communications 15 (1), 5205 , 2024 2024 Citations: 37
The Afrotropical breeding grounds of the Palearctic-African migratory painted lady butterflies ( Vanessa cardui ) G Talavera, A García-Berro, VNK Talla, I Ng’iru, F Bahleman, K Kébé, ... Proceedings of the National Academy of Sciences 120 (16), e2218280120 , 2023 2023 Citations: 26
Metals and metal isotopes incorporation in insect wings: Implications for geolocation and pollution exposure MS Reich, M Kindra, F Dargent, L Hu, DT Flockhart, DR Norris, ... Frontiers in Ecology and Evolution , 2023 2023 Citations: 17
Drought alters the trophic role of an opportunistic generalist in an aquatic ecosystem SL Amundrud, SA Clay-Smith, BL Flynn, KE Higgins, MS Reich, ... Oecologia 189 (3), 733-744 , 2019 2019 Citations: 17
Isotope geolocation and population genomics in Vanessa cardui: Short- and long-distance migrants are genetically undifferentiated MS Reich, D Shipilina, V Talla, F Bahleman, K Kébé, JL Berger, ... PNAS nexus 4 (2), pgae586 , 2025 2025 Citations: 15
Pollen metabarcoding reveals the origin and multigenerational migratory pathway of an intercontinental-scale butterfly outbreak JL Gorki, R López-Mañas, L Sáez, M Menchetti, N Shapoval, A Andersen, ... Current Biology 34 (12), 2684-2692. e6 , 2024 2024 Citations: 15
Erratic spatiotemporal vegetation growth anomalies drive population outbreaks in a trans-Saharan insect migrant R López-Mañas, JP Pascual-Díaz, A García-Berro, F Bahleman, ... Proceedings of the National Academy of Sciences 119 (19), e2121249119 , 2022 2022 Citations: 15
Trans-Saharan migratory patterns in Vanessa cardui and evidence for a southward leapfrog migration MS Reich, S Ghouri, S Zabudsky, L Hu, M Le Corre, I Ng’iru, D Benyamini, ... iScience 27 (12) , 2024 2024 Citations: 13
Temporal stability of δ²H in insect tissues: Implications for isotope-based geographic assignments EE Lindroos, CP Bataille, PW Holder, G Talavera, MS Reich Frontiers in Ecology and Evolution 11, 45 , 2023 2023 Citations: 13
An ensemble machine learning bioavailable strontium isoscape for Eastern Canada M Le Corre, F Dargent, V Grimes, J Wright, SD Côté, MS Reich, ... Facets 10, 1-17 , 2025 2025 Citations: 11
Characterizing eastern spruce budworm’s large-scale dispersal events through flight behavior and stable isotope analyses F Dargent, JN Candau, K Studens, KH Perrault, MS Reich, CP Bataille Frontiers in Ecology and Evolution , 2023 2023 Citations: 11
A hydrogen isoscape for tracing the migration of herbivorous lepidopterans across the Afro‐Palearctic range S Ghouri, MS Reich, R Lopez‐Mañas, G Talavera, GJ Bowen, R Vila, ... Rapid Communications in Mass Spectrometry 38 (3), e9675 , 2024 2024 Citations: 7
Advancements in Isotopic Geolocation Tools for Insect Migration Research M Reich Université d'Ottawa/University of Ottawa , 2024 2024 Citations: 2
Comprehensive analysis of the elemental composition and isotope ratios of honeys from US East Coast ÁZ Ragyák, T Varga, NAK Ahmed, M Braun, A Horváth, Z Lisztes-Szabó, ... Food Chemistry, 149254 , 2026 2026
An integrated framework to identify and characterize regional‐scale insect dispersal F Dargent, MS Reich, M Miller, K Studens, N Benvidi, K Perrault, ... Ecological Applications 36 (3), e70230 , 2026 2026
