Range Shifts Research Articles

A multicontinental dataset of butterfly thermal physiological traits

Butterflies serve as key indicators of climate change impacts such as shifts in emergence timing and shifts in geographic range and distribution. However, the development of commonly used ecological forecasts based on butterfly physiological tolerance of temperature change has lagged behind that of other taxonomic groups. Here, we provide a series of related datasets comprising butterfly thermal physiological traits to enable such forecasts. We compiled data from the literature on butterfly heat and cold tolerance (critical thermal maxima and minima) for 117 species as well as heat resistance (knockdown time) for 45 species. We also present a new dataset comprising heat and cold tolerance and thermal sensitivity of metabolic rate of 28 common North American butterfly species. We envision these data to not only provide foundations for contemporary ecological forecasts of vulnerability to recent climate change, but also to aid in our understanding of butterfly ecology and evolution over historical timescales.

Climate Change Effects on the Only Western Palearctic Plethodontids: Range Changes and Possible Depletion of Intraspecific Genetic Diversity

ABSTRACTAimAmphibians are particularly sensitive to rapid climatic shifts, due to their eco‐physiology, life history traits and high frequency of narrowly distributed species. The genus Speleomantes encompasses the only extant Western Palearctic plethodontids, with three species occurring in peninsular Italy and the remaining five endemic to Sardinia Island.Given the restricted ranges of Speleomantes species and their vulnerability to environmental change, we implemented Ecological Niche Models (ENMs) to estimate the likely impacts of various global warming scenarios on the extent and geographical location of climatically suitable areas.Time PeriodCurrent, with ENMs projected to 2030, 2050 and 2070 under alternative Shared Socioeconomic Pathways.LocationItalian Peninsula and Sardinia Island.Major Taxa StudiedSpeleomantes Dubois 1984 (Caudata: Plethodontidae).MethodsEnsembles of ENMs were fitted for each Speleomantes species, using the ‘biomod2’ modelling platform in R environment. Then, post‐modelling analyses were applied in GIS environment to highlight: (i) the primary geographic direction of predicted suitability shifts for each species and (ii) the proportion of stable, gained and lost suitable areas for each genetic lineage of the single species.ResultsWe found a noticeable shrinking of suitable areas for all Speleomantes species, being particularly extensive under ‘business‐as‐usual’ scenarios for the Sardinian ones. Moreover, core suitable areas were predicted to shift for most species and suitability losses emerged to differently affect distinct genetic lineages, posing additional challenges for designing effective conservation measures.Main ConclusionsThe predicted shrinkage and shifting of climatically suitable areas for most Speleomantes species point to the urgency of evaluating in due time alternative conservation strategies for these endemic urodeles, to prevent losses of taxonomic and genetic diversity. Our modelling framework may be applied to other species with similar traits (e.g., low dispersal ability and narrow environmental niche breadth) to predict climate‐induced range contractions or shifts, using the gained information to optimise conservation outcomes.

Author Correction: Aligning renewable energy expansion with climate-driven range shifts

Author Correction: Aligning renewable energy expansion with climate-driven range shifts

Optimization Design of Pt/C Multilayer Supermirrorsfor Hard X-rays

Aperiodic multilayers have important applications in hard X-rays astronomical observations due to their broadband responses. This paper presents an optimization model of Pt/C power-law graded stack multilayers using the IMD software. The reflectivity expression of multilayers was derived from the reflection theory of X-ray multilayers and Fresnel recursion formulas. Then, the effects of maximum bi-layer thickness ([Formula: see text]), ratio of high-density material thickness to bi-layer thickness ([Formula: see text]), power-law index ([Formula: see text]), number of bi-layers ([Formula: see text]), grazing incidence angle ([Formula: see text]), interfacial roughness ([Formula: see text]), and photon energy ([Formula: see text]) on the reflectivity were analyzed. The calculation results showed that the [Formula: see text], [Formula: see text] and [Formula: see text] control the shift of response range, absorption peak and Bragg peaks, respectively. And the decrease of [Formula: see text] and increase of [Formula: see text] and [Formula: see text] can result in the reduction of reflectivity at different energies. Additionally, an optimized multilayer structure was proposed according to the extremum of merit function, which can achieve a broadband reflectivity of no less than 0.6 from 1[Formula: see text]keV up to 80[Formula: see text]keV. These results can provide important references for the response characteristic analysis and optimization design of multilayers.

Habitat fragmentation mediates the mechanisms underlying long-term climate-driven thermophilization in birds

Climatic warming can shift community composition driven by the colonization-extinction dynamics of species with different thermal preferences; but simultaneously, habitat fragmentation can mediate species’ responses to warming. As this potential interactive effect has proven difficult to test empirically, we collected data on birds over 10 years of climate warming in a reservoir subtropical island system that was formed 65 years ago. We investigated how the mechanisms underlying climate-driven directional change in community composition were mediated by habitat fragmentation. We found thermophilization driven by increasing warm-adapted species and decreasing cold-adapted species in terms of trends in colonization rate, extinction rate, occupancy rate and population size. Critically, colonization rates of warm-adapted species increased faster temporally on smaller or less isolated islands; cold-adapted species generally were lost more quickly temporally on closer islands. This provides support for dispersal limitation and microclimate buffering as primary proxies by which habitat fragmentation mediates species range shift. Overall, this study advances our understanding of biodiversity responses to interacting global change drivers.

Temperate Intertidal Ecosystems are Functionally Richer but More Vulnerable to Loss Than Tropical Ecosystems.

Gastropods are major contributors to a range of key ecosystem services on intertidal rock platforms, supporting trophic structure in both terrestrial and marine contexts and manipulating habitat complexity. However, the functional structure of these assemblages is rarely examined across broad spatial scales. Here, we describe patterns in gastropod functional diversity, redundancy and vulnerability to functional loss across a latitudinal gradient following the west coast of Australia (18° S-34° S). Specifically, we created a trait matrix based on six categorical traits for 186 gastropod species from 39 sites to examine how trait composition varied with latitude. We found there was no latitudinal gradient in either functional richness or distinctiveness despite clear gradients in species richness and taxonomic distinctiveness, which both increased towards the equator. We delineated two distinct functional bioregions, a temperate south (34° S-27° S) and a tropical north (24° S-18° S), and found that the temperate bioregion had greater functional richness and uniqueness but lower redundancy compared to the tropical bioregion. Our findings show that gastropod assemblages in the temperate bioregion are more vulnerable to functional loss as their functional entities are supported by fewer or even single species. Comparatively, the tropical bioregion reported higher redundancies, which could provide a buffer against future change. Understanding the functional structure of intertidal ecosystems is vital as gastropods face the uncertain impacts of coastal tropicalisation, range shifts and sea level rise.

Organisms with high dispersal ability as a proxy for biogeographical characterisation of the Mediterranean biome

The Mediterranean biome offers a diverse range of habitats, particularly rocky environments, known for their long-term stability and persistence. Adapted to these rocky surfaces, chasmophytes thrive in this region, benefiting from reduced competition and human interference. The distribution of stress-tolerant cryptogams with generally broad niches represents a significant gap in the biogeography of the region. This study investigates whether complex symbiotic organisms with a potential for long-distance dispersal could serve as biogeographic indicators for delimitation of the Mediterranean biome's boundaries. Through comprehensive chorology data research, saxicolous lichen congeners of the genus Solenopsora were mapped across the Mediterranean Basin as a model area. Environmental predictors (climate and geology) were employed to predict suitable habitats, shedding light on the lichens' ecological niches. Habitat suitability models consistently aligned with the Mediterranean's geographical area, indicating a tight link between lichen distribution and Mediterranean climate classification. While climate change may pose vulnerabilities, no significant range shifts beyond the latitudinal limit of the Mediterranean were predicted. Despite overlapping climatic niches, differences in microhabitat preferences in terms of insolation were observed among studied taxa. Vulnerable regions with potential habitat decreases were identified under future scenarios, emphasizing the importance of environmental heterogeneity in securing local species persistence. This study supports the hypothesis that these lichen symbiotic systems are restricted to the Mediterranean Basin, highlighting their potential to reflect Mediterranean climate, environmental stability, and indicate the boundaries of the Mediterranean biome. Our investigation demonstrates that collection-based research can yield significant contributions to current biogeography.

Evidence for the importance of trophically transmitted parasites and predation at the lower latitudes of species ranges.

The lack of information concerning how parasitism maps onto host geographical distributions represents a striking gap in ecological knowledge. This knowledge gap limits our understanding of a wide range of phenomena, including the consequences of climate change-induced range shifts of both hosts and parasites. To help solve this problem, we created a predictive theoretical framework and quantified latitudinal variation in parasitism by animal and protozoan parasites throughout the entire contiguous geographical ranges of four estuarine fish species. To circumvent frequent limitations in data and to permit revealing of novel biogeographical patterns, we (i) quantified parasitism at the individual host level, (ii) quantified parasite species diversity and biomass load, and (iii) tracked functionally distinct parasitic consumer strategies. Parasite diversity always increased at lower latitudes, and this pattern was largely driven by parasites using trophic transmission. Furthermore, in three of four cases, the role of fish as predator- versus prey-host for trophically transmitted parasite (TTP) species increased at lower latitudes. Parasite diversity patterns followed predictions more consistently than did biomass load, indicating that increased predation at lower latitudes may decrease observed parasite biomass load. These findings suggest a particularly strong role for TTPs and predation in community structure and dynamics at lower latitudes.

Changes in Distribution Ranges of Abies Species Dominating in the Forests of Northeast Asia Since the Last Glacial Maximum

ABSTRACTAimClimate variations within the stadial–interstadial cycles drive shifts in the distribution of forest dominants. This study examines how climate dynamic alters the distribution ranges of two boreal and one cold‐temperate Abies species dominating in Northeast Asia.LocationNortheast Asia: China, Japan, Korea and Russia.TaxonAbies nephrolepis, A. sachalinensis (sect. Balsamea) and A. holophylla (sect. Pseudopicea).MethodsWe developed climate envelope species distribution models (SDMs) using warmth and coldness indices, the continentality index, and proxies of rain and snow precipitation indices. We interpolated SDMs on reconstructed climates for the Last Glacial Maximum (LGM) and the Holocene Climatic Optimum (HCO) and to predicted climates for 2070 under global warming scenarios RCP2.6 and RCP8.5.ResultsDuring the LGM, the climatic optimum for all species covered extensive areas on the shelves of the Japanese and Yellow Seas, facilitated by the global sea level drop. The interglacial climatic optimum supports the expansion of A. nephrolepis and A. sachalinensis compared to the LGM, whereas the range of A. holophylla climatic niche range experiences a reduction.Main ConclusionsOur findings highlight the significant impact of climatic oscillations on the spatial distribution and ecological dynamics of Abies species in Northeast Asia. The contrasting responses of boreal and temperate fir species to glacial and interglacial periods underscore the complex interplay between climate change and the distribution of forest dominants. Projections under future warming scenarios suggest that Abies species will face further range shifts, emphasising the need for adaptive forest management and conservation strategies, especially in the southern part of their distribution.

No Sign of Homogenisation in Reef Fish Communities Across an Ecological Transition Zone Exposed to Warming

ABSTRACTAimMarine organisms are responding to warming by altering their distribution ranges, causing biogeographic range shifts and in some cases, favouring the community homogenisation. Transition zones can act as natural laboratories to explore the consequences of homogenisation. However, these habitats are relatively poorly studied in coastal areas. In this study, we aimed to investigate biotic homogenisation and changes in reef fish community composition from both a taxonomic and trait‐based perspective.LocationSeven islands in the South‐western Atlantic transition zone.MethodsWe used a long‐term survey data set of reef fish species abundances and traits of communities to calculate beta‐diversity indices. By analysing the data, we derived temporal trends of beta‐diversity values by separately comparing the North and South regions of the transition zone and performed pairwise comparisons to explore their dynamics when considered together.ResultsContrary to previous expectations, we found no sign of homogenisation. The colder islands (Southern) experienced a decrease in taxonomic and trait richness metrics, whereas for the warmer islands (Northern), the taxonomic and trait richness fluctuated without any significant temporal trends.Main ConclusionsWhile taxonomic composition may change over time, the trait composition is generally more conserved, highlighting the trait redundancy in South‐western Atlantic communities and supporting the idea that these communities can maintain a range of ecological processes despite changes in taxonomic composition. Finally, the study revealed that despite non‐homogenisation, the species that contribute most to variation, especially in the South, have common trait combinations indicating an increase in the trait redundancy of fish communities over time. We underline that local‐scale conservation efforts may be particularly effective in preserving and protecting species and ecological functions in areas experiencing unique and fast changes in biodiversity.

Combining past and contemporary species occurrences with ordinal species distribution modeling to investigate responses to climate change

Many organisms leave evidence of their former occurrence, such as scat, abandoned burrows, middens, ancient eDNA or fossils, which indicate areas from which a species has since disappeared. However, combining this evidence with contemporary occurrences within a single modeling framework remains challenging. Traditional binary species‐distribution modeling reduces occurrence to two temporally coarse states (present/absent), so thus cannot leverage the information inherent in temporal sequences of evidence of past occurrence. In contrast, ordinal modeling can use the natural time‐varying order of states (e.g. never occupied versus previously occupied versus currently occupied) to provide greater insights into range shifts. We demonstrate the power of ordinal modeling for identifying the major influences of biogeographic and climatic variables on current and past occupancy of the American pika Ochotona princeps, a climate‐sensitive mammal. Sampling over five years across the species' southernmost, warm‐edge range limit, we tested the effects of these variables at 570 habitat patches where occurrence was classified either as binary or ordinal. The two analyses produced different top models and predictors – ordinal modeling highlighted chronic cold as the most‐important predictor of occurrence, whereas binary modeling indicated primacy of average summer‐long temperatures. Colder wintertime temperatures were associated in ordinal models with higher likelihood of occurrence, which we hypothesize reflect longer retention of insulative and meltwater‐provisioning snowpacks. Our binary results mirrored those of other past pika investigations employing binary analysis, wherein warmer temperatures decrease likelihood of occurrence. Because both ordinal‐ and binary‐analysis top models included climatic and biogeographic factors, results constitute important considerations for climate‐adaptation planning. Cross‐time evidences of species occurrences remain underutilized for assessing responses to climate change. Compared to multi‐state occupancy modeling, which presumes all states occur in the same time period, ordinal models enable use of historical evidence of species' occurrence to identify factors driving species' distributions more finely across time.

Climate-driven distributional shifts in Chocó endemic birds of southwest Colombia

IntroductionClimate change poses a significant threat to bird communities, especially forest-dwelling and narrowly distributed species, which are expected to experience severe range contractions and higher extinction risks compared to widely distributed and open-area species. The Chocó region in southwestern Colombia, known for its rich bird endemism, is particularly vulnerable.MethodsWe analyzed potential distribution shifts for 27 endemic and near-endemic bird species in the Chocó region using eBird occurrence records and climate projections. We modeled species distributions under low and high greenhouse gas emission scenarios for 2050 and 2070, comparing these projected distributions to current forested and protected areas to evaluate future conservation needs.ResultsOur findings indicate that nearly all species are projected to lose climate-suitable areas under at least one future scenario, resulting in a regional decline in species richness. Changes in species richness are most pronounced near the Colombia-Ecuador border, suggesting a shift to higher elevations. Notably, the Scarlet-and-white Tanager (Chrysothlypis salmoni) is predicted to suffer the greatest losses in climate-suitable area, both within protected and forested regions.DiscussionThese results highlight the urgency of expanding the protected area network and conserving key forested regions to help species adapt to climate change. By providing projected distribution maps and potential range shifts, our study underscores the importance of modeling future distributions to support conservation strategies for at-risk species and the ecological services they provide in tropical montane regions.

Movement patterns of green turtles at a key foraging site: the Banc d’Arguin, Mauritania

AbstractInteractions with fisheries is a major threat to sea turtles. However, space-use at foraging locations remains overlooked in many populations, preventing effective protection. We assess the space-use of 14 juvenile and 24 adult green turtles (Chelonia mydas) satellite-tracked in 2018–2022 within a foraging site of global importance for this species, the Banc d’Arguin in Mauritania, West Africa. Turtles exhibited a patchy distribution and used overlapping habitats irrespective of sexes and life stages. Mean individual home range was larger (151.5 ± 160.5 km²) than values reported in most green turtle populations. Individuals concentrated in two main areas used year-round. Inshore/offshore movements seem to occur within the central part of the Banc d’Arguin, with turtles moving to deeper areas during colder months. More than half of the turtles performed within-season range shifts and switched between up to four distinct areas, with some individuals returning to previously visited sites. Turtles mostly exploited shallow areas (4.30 ± 3.42 m) and seemed to use disproportionally more of the areas inside the Parc National du Banc d’Arguin, than areas of similar bathymetry outside this marine protected area. This suggests that foraging green turtles have been benefiting from the management of the Park since it was established in 1976. However, turtles’ home range overlapped greatly with artisanal fisheries, which operate in the central shallow waters of the Park. The present study provides valuable ecological information that can be used to inform the planning of fisheries management zones, aiming to reduce the interactions between turtles and artisanal fisheries.

Weather Radars Reveal Environmental Conditions for High Altitude Insect Movement Through the Aerosphere

High-flying insects that exploit tropospheric winds can disperse over far greater distances in a single generation than species restricted to below-canopy flight. However, the ecological consequences of such long-range dispersal remain poorly understood. For example, high-altitude dispersal may facilitate more rapid range shifts in these species and reduce their sensitivity to habitat fragmentation, in contrast to low-flying insects that rely more on terrestrial patch networks. Previous studies have primarily used surface-level variables with limited spatial coverage to explore dispersal timing and movement. In this study, we introduce a novel application of niche modelling to insect aeroecology by examining the relationship between a comprehensive set of atmospheric conditions and high-flying insect activity in the troposphere, as detected by weather surveillance radars (WSRs). We reveal correlations between large-scale dispersal events and atmospheric conditions, identifying key variables that influence dispersal behaviour. By incorporating high-altitude atmospheric conditions into niche models, we achieve significantly higher predictive accuracy compared with models based solely on surface-level conditions. Key predictive factors include the proportion of arable land, altitude, temperature, and relative humidity.

Shrinking horizons: Climate-induced range shifts and conservation status of hickory trees (Carya Nutt.)

Understanding the intricate interplay between the geographic distributions of species and the dynamics of environmental factors is crucial for effective biodiversity management. Crop wild relatives are important resources for the improvement of cultivated plants. However, our understanding of how these species might respond to future climatic changes and their implications for conservation remains incomplete. In this study, we focus on the ecologically and economically significant hickory trees to address this knowledge gap. We employed the Biomod2 ensemble model to predict the potential distributions of 12 North American Carya species and five East Asian based on 13,643 occurrence points and 26 environmental variables. We analyzed the distribution range dynamics of hickory trees across the past, present, and future emission scenarios (2090; SSP126 and SSP585), assessed their conservation status, and conducted a preliminary threat assessment. Our results indicate that most Carya species expanded their habitat range from the Last Glacial Maximum to the present, with substantial contraction projected under both future scenarios. A northward migration shift to high elevations was observed for most species from the LGM to the future. Sixteen species were categorized as “medium priority” for further conservation action, and only one (C. tonkinensis) as “high priority”. Preliminary threat assessment classified one species (C. luana) as critically endangered, eight endangered, four vulnerable, and five as least concern. This study underscores the potential effects of climate change on the distribution of Carya species, providing crucial insights for their conservation and highlighting the broader impacts of climate change on crop wild relatives.

Forecasting range shifts using abundance distributions along environmental gradients

Globally, many species’ distributions are shifting in response to contemporary climate change. However, the direction and rate of shifts remain difficult to predict, impeding managers’ abilities to optimize resource allocation. Here, we developed a new approach for forecasting species range‐limit shifts that requires only abundance data along environmental (for example, elevational) gradients. We posited that the distribution of species’ abundances could offer insights into the potential for future range‐limit shifts. We then tested this prediction using data from several transect studies that compared historical and contemporary distributions. Consistent with our prediction, we found that strong asymmetry in abundance distributions (that is, “leaning” distributions) indeed preceded species’ lower‐limit range shifts. Accordingly, surveying abundances along environmental gradients may represent a promising, cost‐effective method for forecasting local shifts. Ideally, this approach will be incorporated by practitioners into species‐specific management planning and will inform on‐the‐ground conservation efforts.

Evaluating and elevating the role of wildlife road crossings in climate adaptation

Beyond the well‐established benefits of wildlife road crossings and associated infrastructure—improving driver safety, reducing animal mortality, reconnecting habitats—there is another important but often underappreciated benefit: supporting wildlife and ecosystems in adapting to climate change. We explore this potential by (1) synthesizing the literature surrounding climate adaptation and wildlife crossings, (2) presenting a case study on how crossings support shifting animal migrations, and (3) describing key considerations for incorporating climate information into crossing prioritizations. Among other climate‐adaptive benefits, research suggests crossings can support species range shifts and protect access to resources even as drought and human development compromise that access. Our case study outlines an approach for prioritizing crossing locations most likely to support animal migration both today and into the future. By accounting for such dynamics, wildlife crossings can be a cost‐effective tool that protects wildlife as well as motorists and enhances the resilience of infrastructure and ecosystems in a changing world.

Tracing the range shifts of African tree ferns: Insights from the last glacial maximum and beyond

African tropical forests are experiencing rapid decline as a result of several factors, including increasing population pressure, recurrent wildfires, selective logging practices, land use changes, intensified agricultural activities, and other social and economic issues. Using MaxEnt, paleoclimatic data, and future climate scenarios, the present study seeks to explore the presence of tree ferns in tropical and Saharan Africa during the Last Glacial Maximum, African Holocene Humid Period (AHHP; ca. 14,500–5000 years ago) and to project the effects of climate change on the distribution of tree ferns in Africa under two future climatic scenarios, Representation Concentration Pathways (RCP) 4.5 and 8.5. Our study reveals that despite a significant increase in precipitation during the AHHP, precipitation distribution was variable and insufficient to support the five tree fern species examined in this study. While some tree fern species have experienced range shifts over time, we found that most of them have maintained their presence within refuge areas that probably endured the late Pleistocene extinction event. These refugia provided a haven for some tree ferns, allowing them to persist and survive amidst challenging and varying environmental conditions. This highlights tree ferns' remarkable adaptability in changing climate as well as the critical importance of these refugial areas in safeguarding their populations during climatic upheaval. Our study further demonstrates that different species respond to climate change differently, with some experiencing minimal range contractions of 2.0 %, up to more than 57.0 % range expansion in other species. Preserving refugia not only safeguards tree fern populations but also contributes to conserving overall forest biodiversity and ecosystem functioning. This knowledge is crucial for implementing targeted conservation actions that promote sustainable forest management and can mitigate the threats posed by climate change and anthropogenic activities in African closed wet forests.

VeTAPRH: A Taxonomic Assignment Protocol for Vertebrates Applied to eDNA Metabarcoding Data, Including Molecular, Taxonomic and Ecological Criteria

Exploring biodiversity requires meticulous species identification within specific environments. Environmental DNA (eDNA) refers to DNA extracted from environmental samples (Taberlet et al. 2018). Using metabarcoding with eDNA enables detailed taxonomic inventories (Valentini et al. 2009, Haderlé et al. 2024). After sample collection, DNA is extracted, the targeted barcode is amplified, and obtained amplicons are sequenced, producing millions of sequences. Bioinformatics processing is then a particularly important step in the analysis used to clean, structure sequences and complete taxonomic assignments. However, computerized protocols face limitations, including taxonomic misidentifications due to intraspecific variation, such as in the Delphininae (Alfonsi et al. 2013), or incomplete reference databases (e.g. Hleap et al. 2021, Meglécz 2023). Relying on custom databases may help but can miss unexpected taxa range shifts (Gold et al. 2021, Jung et al. 2016). Including ecological data (Coissac et al. 2012, Deiner et al. 2017, Blackman et al. 2023) or integrating multiple databases (Bourret et al. 2023) enhances accuracy, and expert validation remains essential (Clarke et al. 2017, Porter and Hajibabaei 2018). Our study aims to develop a taxonomic assignment protocol for vertebrate Molecular Operational Taxonomic Units (MOTUs)/Amplicon Sequence Variants (ASVs), called VeTAPRH (Vertebrates Taxonomic Assignment Protocol), to verify automated assignments from metabarcoding pipelines. This protocol generates successive species lists, first built on the basis of molecularly similar taxa, then successively refined on the basis of taxonomic data and plausibility of local distribution, compiled from specialized databases. By cross-referencing these criteria, we establish a list of hypothetical taxa for each MOTU, including those absent from reference databases. Initially presented as a flowchart, this protocol will lay the groundwork for a digital tool to support taxonomists.

Inter-center comparison of proton range verification prototypes with an anthropomorphic head phantom**F. Hueso-González and J. Berthold share first authorship. J. Verburg and C. Richter share last authorship. P. Wohlfahrt was essential for the work conception, treatment planning design and equalization, and for the transatlantic transport of the phantom.

Objective. To compare in reproducible and equalized conditions the performance of two independent proton range verification systems based on prompt gamma-ray detectors from two different proton therapy centers.Approach. An anthropomorphic head phantom with calibrated stopping power, serving as ground truth, was irradiated with comparable treatment plans, spot positions and energies in both facilities. Clinical beam current, tumor contour and dose were used. The absolute range measurement was compared to the expected value according to the ground truth. The statistical precision was assessed by repeating each measurement ten times. Sensitivity to relative range shifts was evaluated by introducing 2 mm and 5 mm plastic slabs on half of the field.Main results. The resulting absolute range accuracy was within 2.4 mm in all cases. Relative range shifts were detected with deviations lower than 14%.Significance. The performance of both systems was deemed worthy of clinical application for the detection of range deviations. This study represents the first comparison of independent prompt gamma-ray-based proton range verification systems under equalized conditions with realistic treatment fields and beam currents.