Southwestern Alps Research Articles

Elachistadimicatella sensu auctt.-a complex of neglected species diversity (Lepidoptera, Elachistidae) from European mountain systems.

Elachistadimicatella Rebel, 1903, has so far been considered a species in Europe with restricted distribution from Ukraine to western France. The species occurs on mountainous regions. However, the in-depth analysis of a taxonomically uncertain species of Elachista from the Cottian Alps (Italy), especially through DNA barcoding and subsequent morphological studies, led to the realization that individuals previously identified as E.dimicatella from the Cottian Alps and the Pyrenees were misidentified. According to our research, a total of three species can be differentiated: E.dimicatella from Carpathians and its former junior synonym E.niphadophanes Meyrick, 1937, sp. rev., from the Pyrenees, as well as the newly described E.cottiella sp. nov. from southwestern Alps, hitherto incorrectly identified as E.dimicatella. Diagnostic features of the three species are discussed and illustrated. Elachistadimicatella and E.niphadophanes are redescribed.

The Briançonnais margin units in the South-Western Alps (Italy-France)

The Briançonnais margin units in the South-Western Alps (Italy-France)

Past and current climate as a driver in shaping the distribution of the Longitarsus candidulus species group (Coleoptera: Chrysomelidae).

Longitarsus candidulus (Foudras) is a thermophilic flea beetle species widely distributed in the Mediterranean Basin and associated with Daphne gnidium L. and Thymelaea hirsuta (L.). Longitarsus laureolae Biondi and Longitarsus leonardii Doguet, phylogenetically closely related to L. candidulus, show together a peculiar and rare disjunct distribution along the central-southern Apennines and the Cantabrian-Pyrenean mountain system, respectively. Both are associated with Daphne laureola L. in mesophilic habitats. We used "ecological niche modeling" to infer the Pleistocene dynamics in the distribution of the three flea beetle species and their host plants. We interpreted their current distributions, paying particular attention to the presumed time of species divergence as inferred from recent studies. The differentiation of L. laureolae and L. leonardii from L. candidulus likely represents a response to the marked climatic changes during the Late Pliocene. Such a split was likely associated with a trophic niche shift of the laureolae/leonardii ancestor towards the typically mesophilic host plant D. laureola. The subsequent split between L. laureolae and L. leonardii, possibly due at first to the niche competition, was then boosted by an allopatric divergence during the Middle Pleistocene, likely caused by a large area of low environmental suitability for both species, mainly located between the northern Apennines and the south-western Alps.

DNA barcoding reveals a new cryptic species of Denisia Hübner, 1825 (Lepidoptera, Oecophoridae) from the south-western Alps

A new species of concealer moths (Oecophoridae), Denisia crypticasp. nov., is described from specimens collected in the south-western Alps (Italy, France). It differs from similar congeneric taxa of the Denisia stipella species-group by a combined pattern of colour and markings of the forewing upperside, the colour of the head, particularly the yellow second segment of the labial palpi, and by highly divergent DNA barcode (cytochrome c-oxidase subunit 1) sequences. Male and female genitalia are like several other species, with only subtle diagnostic characters. Adult and partially genitalia of D. crypticasp. nov. and the closest European species are shown for comparison. Finally, a complete checklist of European species of Denisia is added.

Unveiling the hypotheses of endemic richness: A study case in the Southwestern Alps

Areas where range-restricted species are concentrated are of importance for conservation. However, most of the studies aim at identifying areas rich in endemics for conservation planning, while few studies aim at understanding the causal factors of endemic richness. Here, our goal is to identify the determinants of endemic richness within a centre of endemism, the Southwestern European Alps, by testing four non-mutually exclusive hypotheses that have been proposed to explain patterns of endemic richness. In particular, we examined to what extent temporal and spatial climatic stability and environmental heterogeneity are related to endemic richness. Almost all hypotheses partially support the observed patterns of plant endemics richness within the SW Alps. In general, most of the relationships between environmental variables and endemic richness are statistically significant. However, the highest effect in explaining endemic richness is found for climate change velocity and standard deviation of slope, two factors affecting the possibility of species to disperse. This is in line with the idea that endemics are strongly limited by dispersal and not only by climate. Our results suggest that in regions where the effects of past climate changes were less dramatic endemic richness results from the interaction of species dispersal with regional and specific historical factors.

3D geometrical modelling of the non-cylindrical Vélodrome Miocene fold in the southwestern Alps

Fold geometries and kinematics within foreland basins is a major issue for understanding the late evolution of thrust fronts. In the foreland of the southwestern Alps, the Vélodrome complex fold involves the whole Tertiary series which have recorded the evolution of the alpine front. From a geometrical and kinematic point of view, the Vélodrome is classically described as a recumbent Mio-Pliocene syncline with a strongly curved axis; interpreted either as a classic growth-fold, a post-deposit fold, or a result of coeval salt activity. The debate reveals a lack of consensus on the internal structure of the Vélodrome and the potential role of salt motion. By a detailed field analysis coupled with an implicit 3D geometrical modelling approach, we test the different hypotheses and provide a new 3D illustrated interpretation of the Vélodrome series. The Vélodrome consists in a complex non-cylindrical structure composed by several folds with different orientations together with inter- and intra-formations unconformities. Folding is partly syn-depositional and began earlier in the south, near Esclangon village, than in the north. In the north, deformation started with the marly and sandy molasse (m2, middle Burdigalian), attested by the transition from the conformable conglomeratic marine molasse (m1–2, Aquitanian and early Burdigalian) to the unconformable m2 to the Valensole formation. Deformation began earlier in the south, during the deposition of the m1–2, as shown by internal unconformities. We discuss the ingredients controlling the deformation in the Vélodrome, regional tectonics (mainly since middle Burdigalian) versus salt tectonics. This study further brings new constraints on the timing and pattern of deformation of the southwestern orogenic front of the Alps. It also highlights the power of the 3D geometrical modelling approach for testing different hypotheses and better understanding 3D complex structures.

Changes in taxonomic and functional composition of subalpine plant communities in response to climate change under contrasting conditions of bedrock and snow cover duration

AbstractQuestionsWe assessed interactions between climate change, bedrock types and snow cover duration on the trajectories of taxonomic and functional composition of subalpine plant communities. We predict (i) an increase in species richness on siliceous bedrock due to a reduced competition and a decrease in richness on calcareous bedrock due to increasing drought stress; (ii) decreasing snow cover duration should induce a higher shrub encroachment in hollows as compared to ridges; and (iii) increasing growing season temperature should induce taller sizes and more conservative growth traits, in particular in hollows.LocationSubalpine belt of the Grandes Rousses mountain range, southwestern Alps (France).Methods189 vegetation plots were sampled in 1997 and 2017–2018. The duration of snow cover was assessed during two years in 1995–1997 and five functional traits were measured on 108 species in 2021. We performed multivariate analyses, quantified community‐weighted means (CWM) of traits and used ANOVAs to detect responses to local‐scale factors and changes in snow cover, temperature and precipitation since 1997 according to a nearby meteorological station.ResultsOverall, taxonomic composition weakly changed and changes were more dependent on the position of communities along the snow cover duration gradient than on their bedrock type. The abundance of drought‐tolerant species increased at the border of hollows and there was, over all communities, a slight increase in the abundance of dwarf shrubs and tall herbaceous species, a strong decrease in short herbaceous species and, thus, an overall decrease in species richness. There were important overall changes in CWM of size traits, in particular leaf area which increased the most in hollows irrespective of bedrock types.ConclusionIn this subalpine site the effects of decreasing snow cover duration overwhelmed the effects of bedrocks, which may explain the overall increase in competitive species and decrease in species richness.

18th EDGG Field Workshop - Dry grasslands of South-Western Alps, Aosta, Susa and Durance valleys, Italy and France, 1–11 June 2024. Second Call.

18th EDGG Field Workshop - Dry grasslands of South-Western Alps, Aosta, Susa and Durance valleys, Italy and France, 1–11 June 2024. Second Call.

Molecular evidence and environmental niche evolution at the origin of the disjunct distribution in three mountain endemic Tephroseris (Asteraceae) of the Mediterranean basin

Studies on the origin and evolutionary history of closely related plants help to understand patterns of diversity of the mountain flora in addition to providing the basis for their identification. The genus Tephroseris includes three endemic taxa with small and disjoint distributions in the high mountains of the Iberian Peninsula and on the Maritime Alps. Tephroseris balbisiana is native to the Southwestern Alps, Tephroseris elodes to Sierra Nevada, and Tephroseris coincyi to Sierra de Gredos. These taxa have been treated under different combinations of species or subspecies due to limited morphological differentiation, but comprehensive studies have not been published so far. By combining information from phylogeny, molecular dating and genome size, we demonstrated the taxonomic distinctiveness between T. balbisiana and the two Iberian taxa. Although the lack of variability in plastid DNA hampered the precise estimation of the diversification events, some of the recovered patterns suggested a recent divergence of T. balbisiana, T. elodes and T. coincyi dating back to the Pleistocene (0.5–2.8 Mya). However, niche modeling supported a geographical overlap between the three taxa during the Last Glacial Maximum (LGM). Moreover, the fragmentation of their ancient larger distribution range, particularly in the lower elevations of the Iberian Peninsula, and migration to glacial refuges in the south-western Alps, provide the most plausible explanations for the current disjoint distribution within the Mediterranean mountains. Furthermore, based on the evidence we gathered, we inferred that the alpine T. balbisiana, as well as the Iberian taxa, should be considered as three distinct subspecies.

Tectonic coupling of oceanic and continental units in the Southwestern Alps (Western Liguria, Italy) revealed by structural mapping

ABSTRACT We described the structural architecture of a key area along the Western Ligurian Alps where a stack of oceanic and continental units showing Low- to very Low-grade metamorphic imprint is exposed. We combine a new dataset by integrating stratigraphic, structural and metamorphic data to produce an original 1:12.500 geological map. The high-resolution mapping along with multiscale structural analysis revealed a large-scale superposition of fold and thrust systems extending for more than 50 km2. These field data and available thermobarometric estimates provide constraints to decipher the tectonic evolution of the Southwestern Alps and highlight the shallow crustal coupling of continental and oceanic units during top-to-the-southwest thrusting, the latter was strongly evident in the investigated area.

Will natura 2000 european network of protected areas support conservation of Southwestern Alps endemic flora under future climate?

Networks of protected areas (PAs) are globally recognized as playing a key role for in situ conservation of species. Despite a high potential for biodiversity conservation, PAs may not mitigate the current biodiversity loss because they do not consider climate change impact. In fact, because PAs have static geographical boundaries, they may hardly keep pace with dynamics in species distribution caused by the climate change, which was not considered when they were designed. In this study, we used species distribution modelling of 85 plant taxa endemic or subendemic to Southwestern Alps to evaluate the effectiveness of PAs network in protecting endemics under future climate change scenarios. PAs cover roughly the 30% of the Southwestern Alps. PAs will harbour more expected distribution range of taxa in the future than today, probably because they occur in high altitude areas rich in endemics that have been climatically stable areas in the past and that will likely remain relatively climatically buffered in the future. Moreover, PAs are distributed to poorly cover expected range of endemics at low and middle elevation, which are threatened by urbanization and climate change. We recommend additional protection at low and middle elevation, considering the future climatic suitability of species.

Fluvial bedrock gorges as markers for Late-Quaternary tectonic and climatic forcing in the Southwestern Alps

Fluvial incision is one of the major erosive processes acting at Earth's surface and is highly sensitive to tectonic, isostatic and climatic variations. The aim of this study is to distinguish between the short-term climatic fluctuations versus the long-term tectonic forcing contribution to Late-Quaternary fluvial incision, to better understand its timing and driving mechanism(s). To achieve this goal, we measured in situ-produced 36Cl concentrations along several river-polished gorge walls in Jurassic limestones of the Southwestern Alps. We then compared our dating results to previously-dated river gorges from nearby catchments. This allows us to highlight three trends of distinct incision dynamics, and to discuss their relationships with climate and tectonics. Trend 1 shows the direct impact of a paraglacial crisis in the rivers connected to glaciated areas. Trend 2 suggests an incision wave propagating along the non-glaciated tributaries following enhanced incision in the main streams. Trend 3 displays steady and low incision rates in gorges disconnected from any fluvial response to glacier retreat. Trend 3 also seems to highlight the potential of resistant lithologies to isolate portions of the river network from post-glacial incision propagation. Our analysis shows that gorges connected to upstream glaciers exhibit a significant response of fluvial incision to climatic fluctuations, evidenced by high-amplitudes incision rate variations hindering the long-term tectonic signal. In contrast, incision rates inferred from disconnected gorges are in agreement with previously-estimated long-term denudation and rock-uplift rates in the area. Based on the latter, we can conclude that Late-Quaternary river incision in the Southwestern Alps is readjusting to both short-term climatic forcing and long-term tectonic forcing.

Pre-Orogenic Tectonostratigraphic Evolution of the European Distal Margin-Alpine Tethys Transition Zone in High-Pressure Units of the Southwestern Alps

Geological mapping, stratigraphic observations, and U/Pb dating allow reconstructing the pre-orogenic setting of the transition zone between the distal European passive margin and the Alpine Tethys in the southwestern Alps. Although convergent tectonics overprinted the syn-rift Jurassic tectonic features, our data document an articulated Jurassic physiography. From the distal European passive margin oceanward, we distinguished: the Dronero Unit (the southernmost Dora Maira massif), represents a continental margin composite basement wherein monometamorphic metasediments are interlayered with Late Permian (253.8 ± 2.7 Ma) metavolcanic rocks; the Sampeyre Unit, represents a structural high consisting of Lower Triassic Verrucano-facies siliciclastic metasediments unconformably sealed by Cretaceous calcschist bearing Globotruncana sp.; the Maira Unit, corresponds to a Middle Triassic platform succession detached from the Sampeyre Unit; the Grana Unit, corresponds to a Late Triassic–Late Jurassic platform to basin succession; the Queyras Schistes Lustrès Complex, represents the ocean basin succession. Tectonic slices of Cambrian (513.9 ± 2.7 Ma) metadiorite hosted in the Valmala Shear Zone, separating the Dronero Unit from the underlying (U)HP units of the Dora Maira massif, suggests a potential pre-Alpine activation of the shear zone.

The Geotouristic Project “the Geological Adventure” to the Rescue of an Iconic World Heritage Geosite, the Ammonites Slab of Digne-les-Bains (National Geological Nature Reserve of Haute-Provence and Unesco Global Geopark, France)

Protected under National Nature Reserve, managed by the Departmental Council of the Alpes de Haute-Provence, and labeled UNESCO Geopark, the Ammonites Slab of Digne-les-Bains (SE France) exhibits 1,550 ammonites over a large open-air surface. Despite the virtual absence of special enhancement for the visitors, this spectacular geosite of high scientific and heritage value has played an important role in the years 1990–2000 in the emergence of notions of geological heritage, geological nature reserve, geotourism, and Geopark. Due to its exposure to mountain weather conditions, the Slab suffers from significant conservation issues. Several studies have shown that its condition was much worse than expected. Without major restoration work, the Slab was in danger of collapse in the short term. Given the high cost of the needed rescue work, the geotourism project “The Geological Adventure” was developed under European Interreg ALCOTRA funding. More broadly, this project aims to develop a sustainable experiential geotourism around the geoheritage of the Southwestern Alps cross-border (France–Italy), partly in situ and thanks to digital tools (22 geosites concerned). An important place is given to scientific pedagogy. Concerning the Ammonites Slab, the project consisted of (1) stabilizing and ensuring the sustainability of the fossiliferous layer; (2) planning and developing the overall geosite (parking area, reception area, observation platform); (3) allowing accessibility for people with disabilities; and (4) offering progressive and immersive educational mediation to make scientific culture accessible to as many people as possible.

In-situ Temperature Stations Elucidate Species’ Phenological Responses to Climate in the Alps, but Meteorological and Snow Reanalysis Facilitates Broad Scale and Long-Term Studies

Linking climate variability and change to the phenological response of species is particularly challenging in the context of mountainous terrain. In these environments, elevation and topography lead to a diversity of bioclimatic conditions at fine scales affecting species distribution and phenology. In order to quantify in situ climate conditions for mountain plants, the CREA (Research Center for Alpine Ecosystems) installed 82 temperature stations throughout the southwestern Alps, at different elevations and aspects. Dataloggers at each station provide local measurements of temperature at four heights (5 cm below the soil surface, at the soil surface, 30 cm above the soil surface, and 2 m above ground). Given the significant amount of effort required for station installation and maintenance, we tested whether meteorological data based on the S2M reanalysis could be used instead of station data. Comparison of the two datasets showed that some climate indices, including snow melt-out date and a heat wave index, can vary significantly according to data origin. More general indices such as daily temperature averages were more consistent across datasets, while threshold-based temperature indices showed somewhat lower agreement. Over a 12 year period, the phenological responses of four mountain tree species (ash (Fraxinus excelsior), spruce (Picea abies), hazel (Corylus avellana), birch (Betula pendula)), coal tits (Periparus ater) and common frogs (Rana temporaria) to climate variability were better explained, from both a statistical and ecological standpoint, by indices derived from field stations. Reanalysis data out-performed station data, however, for predicting larch (Larix decidua) budburst date. Overall, our study indicates that the choice of dataset for phenological monitoring ultimately depends on target bioclimatic variables and species, and also on the spatial and temporal scale of the study.

The Maira-Sampeyre and Val Grana Allochthons (south Western Alps): review and new data on the tectonometamorphic evolution of the Briançonnais distal margin

Here we describe the structure, the high-pressure, low-temperature (HP-LT) metamorphism and tectonic evolution of the Briançonnais distal margin units from the south Western Alps. The studied area extends southwest of the Dora-Maira (U)HP basement units and east-southeast of the classical Briançonnais nappes. A new structural map accompanied by geological profiles shows the thrusting of the oceanic nappes (Monviso and Queyras units) onto the distal Briançonnais units (D1 and D2 late Eocene deformation phases) under blueschist-facies conditions. Subsequent deformation during the Early Oligocene (D3 deformation phase) took place under greenschist-facies conditions and was associated with back-folding and -thrusting in the units overlying the Dora-Maira massif and with exhumation related to normal reactivation of former thrusts within the latter massif. Two large cover units, detached from their former distal Briançonnais basement, are redefined as the Maira-Sampeyre and Val Grana Allochthons (shortly: Maira-Grana Allochthons = MGA) including, (i) the Val Maira-Sampeyre unit involving Lower and Middle Triassic formations, seemingly detached from the Dora-Maira units during the subduction process, and (ii) the Val Grana unit with Middle-Upper Triassic and Early-Middle Jurassic formations, which was probably detached from the Maira-Sampeyre unit and correlates with the “Prepiemonte units” known from the Ligurian Alps to the Swiss Prealps. Three major shear zones involving tectonic mélanges of oceanic and continental rocks at the base of the Val Grana, Maira-Sampeyre and Dronero units testify to an early phase of exhumation within the subduction channel in front of the Adria plate. We present a new metamorphic map based on published and new petrological data, including new thermometric data obtained by Raman spectroscopy of carbonaceous material (RSCM). The TRSCM values range from ~ 400 °C to > 500 °C, going from the most external Val Grana unit and overlying Queyras schists to the uppermost Dora-Maira unit. During the Late Triassic, the width of the Briançonnais s.l. domain can be restored at ~ 100 km, whereas it reached ~ 150 km after the Jurassic rifting. A significant, second rifting event affected the Briançonnais domain during the Late Cretaceous-Paleocene, forming the Longet-Alpet chaotic breccias, which deserve further investigations.

The Italian Alpine and Subalpine trouts: Taxonomy, Evolution, and Conservation.

Simple SummaryIn a great part of the world, trout fishing has long inspired human spiritual ideals of immersion into nature and recreation, far removed from the fast-encroaching urbanization. Concurrently, these values and emotions fueled a white-hot business, establishing a florid market of outdoor recreation. Since the 20th century, the trout-culture industry strived to provide anglers with fishing entertainment by stocking massive amounts of non-native trouts in dozens of countries, irrespective of the lakes’ and rivers’ carrying capacity. This had dire consequences on the structural and functional diversity of these ecosystems. “Trout wars” sparked throughout the world between the promoters of stocking activities and the promoters of “wild trout management” and ethics. The “Italian trout war” has been fought on the harsh battleground of trout taxonomy, ecology, distribution, and native vs. non-native interfertile species. Northern Italy, home to the Italian Alpine and subalpine trouts and economic center of the national trout-culture and stocking industry, was particularly affected by this clash. We review here the state of art of this ongoing debate, outlining our scientific view of the taxonomy, evolution, distribution, and sustainable management of the native Italian trouts of northern Italy.During the last 150 years, the trout-culture industry focused on enhancing trout populations by stocking, in response to the growing anglers’ demand and the habitat degradation associated to the rapid urbanization and hydropower development. The industrialized north of Italy, home to the Italian Alpine and subalpine trout populations, is the source of most of the revenues of the national trout-culture industry. Its rapid growth, and the massive introduction of non-native interfertile trouts eroded the genetic diversity of native lineages, leading to harsh confrontations between scientists, institutions, and sportfishing associations. We review here the state of the art of the taxonomy and distribution of the northern Italian native trouts, presenting both scientific results and historical documentation. We think the only native trouts in this region are Salmo marmoratus, widespread in this region, plus small and fragmented populations of S. ghigii, present only in the South-western Alps. We strongly recommend the interruption of stocking of domesticated interfertile non-native trouts in this area, and recommend the adoption of Evolutionary Significant Units for salmonid fishery management. We further propose future research directions for a sustainable approach to the conservation and ecosystem management of the fishery resources and inland waters of northern Italy.

The Moho reflectivity of the subduction beneath the Southwestern Alps from ambient seismic noise autocorrelations

SUMMARY The Western Alps shows a complex crustal organization due to the subduction of the European Plate beneath the Adriatic Plate and exhumation of the mantle wedge. The lithospheric structure of the Western Alps, that may hold significance for understanding orogenic processes and evolution, has been the subject of many geophysical studies, but the Moho profile remains unclear and this has led to controversies about the depth and extent of the European Plate beneath the Adriatic Plate. With the goal of retrieving detailed information on crustal constitution, we use autocorrelation of seismic ambient noise as a tool to map the body wave reflectivity structure at the subduction zone under the southwestern Alps. We use data recorded by the China–Italy–France Alps (CIFALPS) seismic transect, that includes 45 stations located approximately 5–10 km apart along a profile crossing the Alpine continental subduction in the Western Alps. We analyse the data set in four different frequency bands between 0.09 and 2 Hz. We automatically pick the arrival time of the Moho reflection in the second derivative of the envelope of the autocorrelation stack using prior Moho information. The 0.5–1 Hz frequency band mostly gives the best result due to the clear changes in reflectivity along the waveforms of the autocorrelation stacks after the picked arrival times of the Moho reflections. We find spatial coherence between 18 and 23 km depth in the western portion of the profile, indicating relatively homogeneous crustal rocks, and highly reflective structure under the central mountain range, due to the existence of a highly faulted zone. The very thin crust and the underlying mantle wedge known as the Ivrea body show instead high transparency to seismic waves and absence of reflections. The subduction profile of the European Plate shows a steep trend as compared to previous studies. We discuss autocorrelation stacks and Moho depths obtained from the arrival times of the picked reflectivity change in comparison with previous studies to validate the different reflection structures. Stacked ambient noise autocorrelations reliably image varied crustal properties and reflectivity structures in the highly heterogeneous region of the southwestern Alps.

Lithospheric transdimensional ambient-noise tomography of W-Europe: implications for crustal-scale geometry of the W-Alps

SUMMARYA full understanding of the dynamics of mountain ranges such as the Alps requires the integration of available geological and geophysical knowledge into a lithospheric-scale 3-D geological model. As a first stage in the construction of this geo-model, we derive a new 3-D shear wave velocity model of the Alpine region, with a spatial resolution of a few tens of kilometres, making it possible to compare with geological maps. We use four years of continuous vertical-component seismic noise records to compute noise correlations between more than 950 permanent broad-band stations complemented by ∼600 temporary stations from the AlpArray sea-land seismic network and the Cifalps and EASI linear arrays. A specific pre-processing is applied to records of ocean–bottom seismometers in the Liguro-Provençal basin to clean them from instrumental and oceanic noises. We first perform a 2-D transdimensional inversion of the traveltimes of Rayleigh waves to compute group-velocity maps from 4 to $150\, \mathrm{ s}$. The data noise level treated as an unknown parameter is determined with a Hierarchical Bayes method. A Fast Marching Eikonal solver is used to update ray path geometries during the inversion. We use next the group-velocity maps and their uncertainties to derive a 3-D probabilistic Vs model. The probability distributions of Vs at depth and the probability of presence of an interface are estimated at each location by exploring a set of 130 million synthetic four-layer 1-D Vs models. The obtained probabilistic model is refined using a linearized inversion. Throughout the inversion for Vs, we include the water column where necessary. Our Vs model highlights strong along-strike changes of the lithospheric structure, particularly in the subduction complex between the European and Adriatic plates. In the South-Western Alps, our model confirms the existence of a low-velocity structure at $50-80\, \mathrm{ km}$ depth in the continuation of the European continental crust beneath the subduction wedge. This deep low-velocity anomaly progressively disappears towards the North-Western and Central Alps. The European crust includes lower crustal low-velocity zones and a Moho jump of $\sim \, 8-12$ km beneath the western boundary of the External Crystalline Massifs of the North-Western Alps. The striking fit between our Vs model and the receiver function migrated depth section along the Cifalps profile documents the reliability of the Vs model. In light of this reliability and with the aim to building a 3-D geological model, we re-examine the geological structures highlighted along the Cifalps profile.

First evidence of post‐glacial contraction of Alpine endemics: Insights from Berardia subacaulis in the European Alps

AbstractAimLate Quaternary glaciations left an enduring imprint on the distribution of species and their genetic structure. The responses of plants endemic to the Alps can be summarized in three major demographic hypotheses: (i) post‐glacial expansion hypothesis; (ii) post‐glacial contraction hypothesis; and (iii) long‐term stability hypothesis. Here we test these hypotheses and reconstruct the time and extent of demographic responses of an endemic plant to the Late Quaternary climate dynamics.LocationEuropean Alps.TaxonBerardia subacaulis Vill. (Asteraceae).MethodsWe used species distribution models to estimate the paleodistribution of B. subacaulis (Asteraceae) throughout the last 28 Ky and generated genome‐wide sequences to estimate current patterns of spatial structure of genetic diversity. We tested five demographic models by integrating the results of the two independent approaches in an Approximate Bayesian Computation framework.ResultsThe species has weak genetic differentiation among populations, with two main genetic groups. Species distribution models showed a reduction in potentially suitable areas for B. subacaulis during the post‐glacial climate warming and demographic models identified a recent split (2.46 Kya) between the two genetic groups and they slightly supported the post glacial contraction hypothesis.Main conclusionsTaken together, our results support the post‐glacial contraction of an endemic plant, differing from the main pattern observed for endemics species in the European Alps during the Late Quaternary. The different pattern observed in B. subacaulis might be due to several factors, including the less severe effects of glaciations and the environmental heterogeneity of the South Western Alps, combined with some features of the species (i.e. poor dispersal ability, slow growth and microhabitat preferences). Future research in areas where the ice cover was less extensive will contribute to a more complete understanding of the role of climatic changes in shaping the endemics of the European Alps.