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Since its coinage ca. 1850 AD by Philip Barker Webb, the biogeographical region of Macaronesia, consisting of the North Atlantic volcanic archipelagos of the Azores, Madeira with the tiny Selvagens, the Canaries and Cabo Verde, and for some authors different continental coastal strips, has been under dispute. Herein, after a brief introduction on the terminology and purpose of regionalism, we recover the origins of the Macaronesia name, concept and geographical adscription, as well as its biogeographical implications and how different authors have positioned themselves, using distinct terrestrial or marine floristic and/or faunistic taxa distributions and relationships for accepting or rejecting the existence of this biogeographical region. Four main issues related to Macaronesia are thoroughly discussed: (i) its independence from the Mediterranean phytogeographical region; (ii) discrepancies according to different taxa analysed; (iii) its geographical limits and the role of the continental enclave(s), and, (iv) the validity of the phytogeographical region level. We conclude that Macaronesia has its own identity and a sound phytogeographical foundation, and that this is mainly based on three different floristic components that are shared by the Macaronesian core (Madeira and the Canaries) and the outermost archipelagos (Azores and Cabo Verde). These floristic components are: (i) the Palaeotropical‐Tethyan Geoflora, formerly much more widely distributed in Europe and North Africa and currently restricted to the three northern archipelagos (the Azores, Madeira and the Canaries); (ii) the African Rand Flora, still extant in the coastal margins of Africa and Arabia, and present in the southern archipelagos (Madeira, the Canaries and Cabo Verde), and (iii) the Macaronesian neoendemic floristic component, represented in all the archipelagos, a result of allopatric diversification promoted by isolation of Mediterranean ancestors that manage to colonize Central Macaronesia and, from there, the outer archipelagos. Finally, a differentiating floristic component recently colonized the different archipelagos from the nearest continental coast, providing them with different biogeographic flavours. [ABSTRACT FROM AUTHOR]

Motivation: The intrinsic characteristics of islands make them a unique study system for the investigation of ecological and evolutionary dynamics. The Mediterranean Basin, an island‐rich biodiversity hotspot, still lacks a comprehensive spatial database for these geographic features. This study presents the first comprehensive spatial database of all Mediterranean islands larger than 0.01 km2, aiding ecological investigations and interdisciplinary research. Main types of variable contained: The MEDIS spatial database offers detailed information on 39 geographic, climatic, ecological and land‐use variables, including island area, perimeter, isolation metrics, climatic space, terrain data, land cover, palaeogeography, road networks and geological information, providing a multifaceted view of each island's characteristics. Spatial location and grain: The study encompasses 2217 islands in the Mediterranean Basin larger than 0.01 km2. The spatial grain of the datasets on which the selected variables are based varies from 10 m (ESA WorldCover) to 1 km (CHELSA‐BIOCLIM+). Time period and grain: The spatial database incorporates data from various sources, each with its own timeframe, such as the Global Shoreline Vector from 2014 Landsat imagery and the WorldCover dataset from 2021. Historical data like the Paleocoastlines GIS dataset offer insights into island configurations during the Last Glacial Maximum. Major taxa and level of measurement: While not focusing on specific taxa, the study lays the foundation for comprehensive research on Mediterranean islands, facilitating comparisons and investigations into the distribution of native, endemic or alien species. The level of measurement is extensive, encompassing a wide range of variables and providing polygonal features rather than centroids' coordinates. [ABSTRACT FROM AUTHOR]

Background: Tree species represent 20% of the vascular plant species worldwide and they play a crucial role in the global functioning of the biosphere. The Mediterranean Basin is one of the 36 world biodiversity hotspots, and it is estimated that forests covered 82% of the landscape before the first human impacts, thousands of years ago. However, the spatial distribution of the Mediterranean biodiversity is still imperfectly known, and a focus on tree species constitutes a key issue for understanding forest functioning and develop conservation strategies.Methods: We provide the first comprehensive checklist of all native tree taxa (species and subspecies) present in the Mediterranean-European region (from Portugal to Cyprus). We identified some cases of woody species difficult to categorize as trees that we further called "cryptic trees". We collected the occurrences of tree taxa by "administrative regions", i.e. country or large island, and by biogeographical provinces. We studied the species-area relationship, and evaluated the conservation issues for threatened taxa following IUCN criteria.Results: We identified 245 tree taxa that included 210 species and 35 subspecies, belonging to 33 families and 64 genera. It included 46 endemic tree taxa (30 species and 16 subspecies), mainly distributed within a single biogeographical unit. The countries with the highest tree richness are Greece (146 taxa), Italy (133), Albania (122), Spain (155), Macedonia (116), and Croatia (110). The species-area relationship clearly discriminated the richest central-eastern (Balkans) and northern (Alpine and Cevenno-Pyrenean) biogeographical provinces, against the five western provinces in the Iberian Peninsula. We identified 44 unrecognized "cryptic trees", representing 21% of the total trees. Among the 245 taxa identified, 19 are considered to be threatened (15 CR + EN + VU) or near threatened (4 NT) by IUCN.Conclusions: The Mediterranean-European region includes an unsuspectedly high number of tree taxa, almost 200 tree taxa more than in the central European region. This tree diversity is not distributed evenly and culminates in the central-eastern part of the Mediterranean region, whereas some large Tyrrhenian islands shelter several narrow endemic tree taxa. Few taxa are recognized as threatened in the IUCN Red list, and the vulnerability of these species is probably underestimated. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including environmental history on Cavallo island of Corsica in France, inventory of its vascular flora, and analysis of Orchid population.

The aim of this study is to investigate human-climate-environment interactions in a small Mediterranean island. Comparison between palynological and palaeoentomological data fromthe Greco pond (Cavallo Island, southern Corsica) reveals that the islandwas first covered by a more-or-less open Erica arborea pasture-woodland from ca. 7000 to 6100 cal. yr B.P. Grazing animals from 7000 to 6200 cal. yr B.P., followed by a spreading of Ficus carica (marked by the bark beetle Hypoborus ficus) from ca. 6100 to 5750 cal. yr B.P., suggest that human activities could be implicated in the E. arborea forest opening. From ca. 5500 cal. yr B.P., a regional expansion of Q. ilex was recorded, but an open landscape with thermophilous and drought-tolerant plants locally took place from ca. 4700 cal. yr B.P. onward. Pastoral and agricultural biomarkers (pollen, NPP and insect) together with archaeological evidence indicate that human activities were involved in the installation of a lasting open vegetation. Simultaneously, the effects of the Holocene relative sea-level rise on the coastal wetland are recorded: (1) freshwater conditions prevailed in the Greco pond since 7000 cal. yr B.P. at least, (2) the first evidence of salt marsh development dates back to ca. 4500 cal. yr B.P., (3) a strong increase of salinity with marine intrusions were recorded at ca. 3700 cal. yr B.P. while a decline in aquatic insect diversity occurred and (4) a phase of sand dune formationwas recorded fromca. 2000 cal. yr B.P. onward. Our results suggest that if large-scale climatic trend such as the Holocene relative sea-level rise could affect coastal ecosystem, effects of human activities could play the leading role in vegetation and terrestrial beetle assemblage changes in a small island context. [ABSTRACT FROM AUTHOR]

Wetland ecosystems in water-limited environments locally boost biotic interactions, habitat diversity, and species concentrations, but little knowledge exists on their long-term functioning and susceptibility to regime shifts that might influence conservation and reclamation actions. Here we used a historical ecology approach on a rare Mediterranean peat-bog to reconstruct ecological successions for the last 4 millennia. The reconstruction is used to explore the role of geomorphic thresholds, climate changes, and anthropogenic perturbations as drivers of the ecosystem trajectory in the frame of the projected aridification of the climate. Our findings highlight how the superimposition of pastoral disturbances to river incision, has exacerbated ecosystem sensitivity to climate changes. Considering the long-term trajectory, the disappearance of the ecosystem might occur independently of changes in the precipitation regime. Insights given by Historical Ecology have implications for our understanding of ecosystem responses to perturbations, demonstrating that long-term dynamics must be considered before engaging in strict conservation action. [ABSTRACT FROM AUTHOR]

Background and Aims Among the numerous pantropical species of the yam genus, Dioscorea , only a small group occurs in the Mediterranean basin, including two narrow Pyrenean endemics (Borderea clade) and two Mediterranean-wide species (D. communis and D. orientalis , Tamus clade). However, several currently unrecognized species and infraspecific taxa have been described in the Tamus clade due to significant morphological variation associated with D. communis. Our overarching aim was to investigate taxon delimitation in the Tamus clade using an integrative approach combining phylogenomic, spatial and morphological data. Methods We analysed 76 herbarium samples using Hyb-Seq genomic capture to sequence 260 low-copy nuclear genes and plastomes, together with morphometric and environmental modelling approaches. Key Results Phylogenomic reconstructions confirmed that the two previously accepted species of the Tamus clade, D. communis and D. orientalis , are monophyletic and form sister clades. Three subclades showing distinctive geographic patterns were identified within D. communis. These subclades were also identifiable from morphometric and climatic data, and introgression patterns were inferred between subclades in the eastern part of the distribution of D. communis. Conclusions We propose a taxonomy that maintains D. orientalis , endemic to the eastern Mediterranean region, and splits D. communis sensu lato into three species: D. edulis , endemic to Macaronesia (Canary Islands and Madeira); D. cretica , endemic to the eastern Mediterranean region; and D. communis sensu stricto , widespread across western and central Europe. Introgression inferred between D. communis s.s. and D. cretica is likely to be explained by their relatively recent speciation at the end of the Miocene, disjunct isolation in eastern and western Mediterranean glacial refugia and a subsequent westward recolonization of D. communis s.s. Our study shows that the use of integrated genomic, spatial and morphological approaches allows a more robust definition of species boundaries and the identification of species that previous systematic studies failed to uncover. [ABSTRACT FROM AUTHOR]

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. • The drivers of endemic richness are poorly understood. • We tested hypotheses explaining endemic richness to identify causal factors. • The main factor is dispersal possibility. • Dispersal acts in the concurrence with several other drivers. [ABSTRACT FROM AUTHOR]

Aims: Aeolian islands form an active volcanic archipelago. By using updated vascular plant checklists for islands and islets, we tested four hypotheses: (i) Island species–area relationship (ISAR) of alien species has lower c‐ and higher z‐values than native species, (ii) islands with active volcanoes have lower species richness than expected for native and alien species, (iii) ISAR of native species shows lower c‐ and higher z‐values than ISARs of Mediterranean land bridge archipelagos and (iv) species richness of smaller islets is independent of area. Location: Aeolian Archipelago, Mediterranean Basin. Taxon: Vascular plants, identified and named according to the Flora of Italy (Pignatti et al., 2017–2019). Methods: Checklists of native and alien plant species were obtained for eight islands and 24 islets. ISARs were fitted by the Arrhenius power function (S=c·Az) and used to test the first two hypotheses. The third hypothesis was tested by comparing ISAR of Aeolian Archipelago to those from other central and eastern Mediterranean archipelagos. The fourth hypothesis was tested by fitting models defining the presence and limit of the small‐island effect. Results: The checklists included 894 species—749 native and 145 alien. ISARs fitted well for native and alien species and resulted in typical values of c and z parameters. The first and second hypotheses were supported by model fitting. The third hypothesis was not confirmed by the comparison of the ISAR of the Aeolian Archipelago with other archipelagos. The small‐island effect predicted by the fourth hypothesis was supported using S versus LogA for both native and alien species, while for native species it was supported also using the log transformation of the Arrhenius model. Main conclusions: We reported a first comprehensive analysis of plant species richness in the unique Aeolian Archipelago, verifying typical ISARs, no peculiarity with respect to land bridge archipelagos and a somewhat unclear signal for the small‐island effect. [ABSTRACT FROM AUTHOR]

Geographical limits of species' distributions are assumed to be coincident with ecological margins, although this assumption might not always be true. Indeed, harsh environments such as Alpine and Mediterranean ecosystems may favour high phenotypic variability among populations, especially those in peripheral sites. Floral traits are often found to be less variable and less affected by environmental heterogeneity than vegetative traits because variation in the former may have negative effects on fitness. For this reason, it is important to quantify variation in floral traits and plant fecundity in study range limits. The objective of the study is to examine phenotypic variation and differences in reproduction in endemic Lilium pomponium in the Maritime and Ligurian Alps in relation to environmental variation across its distribution range. In this species, marginal climatic populations occur both in the peripheral and central geographical locations of the distribution range; hence, geographical and ecological gradients are not concordant. Floral trait variation is related to local environmental conditions with an array of interactions among resource availability, potential pollen limitation and population size that are differentially related to floral traits. Contrary to the general expectation, all central and peripheral populations had similar, moderate seed production with each group limited by different factors acting on different stages of the life-history strategy. Our results are in line with the idea that general expectations are confirmed only when its assumptions are met and that the differences in pollination environment along an environmental gradient may not be the main determinant of the distribution limit. [ABSTRACT FROM AUTHOR]

• Dracaena draco is able to germinate from 12 °C to 33 °C. • Dracaena draco requires moist and dark conditions to germinate. • Native Dracaena draco occurrences are in areas with temperatures below optimum. The Canary Islands dragon tree (Dracaena draco (L.) L. subsp. draco) is an endangered Tertiary relict species endemic to the Canary and Madeira archipelagos. Based on an ex-situ experiment under controlled conditions, we investigated its germination response to both constant and alternating temperatures, moisture levels (water potential), exposure to light, and desiccation. We found that suitable temperatures for germination (> 5 % of germinated seeds) range from 12.1 °C to 32.8 °C (thermal germination niche limits) and optimal temperatures (> 95 % of germinated seeds) range from 16.6 °C to 28.3 °C. Light exposure and water potential below 0 MPa drastically decreased germination performance while seed desiccation pre-treatments and alternating temperatures had slightly negative effects. Comparing the spatial projection of the thermal germination niche with actual occurrences of D. draco subsp. draco revealed that native populations are mainly distributed in areas where temperatures are colder than the optimum for germination. For native populations, germination rate is predicted to reach 78 % on average based on temperature requirements. Our results suggest that niche conservatism and adaptation are involved in shaping the germination requirements of the dragon tree. [ABSTRACT FROM AUTHOR]

Three decades ago, worldwide biodiversity hotspots were founded on the distributions of continental plants and vertebrates. Here, we question the timeliness of refining the geography of hotspots by basing their definition on more taxa, thanks to the molecular data available for hyper-diverse organisms such as insects, fungi and marine biota. To do so, we assess the temporal dynamic of molecular data acquisition and the geography of knowledge about lineages currently included or not into hotspot definition. Using the Mediterranean Basin hotspot as a case study, we examine the taxonomic and geographical facets of 175,828 DNA sequences distributed over 21,552 species, and 13,001 indexed biodiversity publications. We reveal a deeply fractured repartition of biodiversity research efforts within the hotspot regarding both barcoding efforts and publication activity, the northern side of the Mediterranean concentrating 84.16 % of the publications and 75.99 % of the public DNA sequences. In addition, 57.55 % of the sequences belong to lineages which were excluded from hotspots definition, with highly congruent geographical patterns among marine and continental lineages. Based on this analysis, we suggest 1) using the uneven geography of knowledge to rebalance sampling efforts towards poorly known regions within the Mediterranean hotspot, 2) handling the molecular corpus of orphan lineages to feed forthcoming multi-taxa biodiversity assessment initiatives, in order to 3) refine the geography of conservation stakes within the hotspot by identifying sub-hotspots of global diversity and 4) fusing a broad range of marine and continental taxa in global biodiversity mapping. • Biodiversity hotspots are used to define conservation priorities at global scale. • Hotspots were designed on the distribution patterns of continental macro-organisms. • DNA barcoding offers perspectives to embrace a wider diversity in hotspot definition. • The imbalanced geography of biodiversity knowledge at global scale is challenging. • The Mediterranean basin makes an ideal candidate to explore this perspective. [ABSTRACT FROM AUTHOR]

Microrefugia, defined as small areas maintaining populations of species outside their range margins during environmental extremes, are increasingly recognized for their role in conserving species in the face of climate change. Understanding their microclimatic dynamics becomes crucial with global warming leading to severe temperature and precipitation changes. This study investigates the phenomenon of short-term climatic decoupling within microrefugia and its implications for plant persistence in the Mediterranean region of southeastern France. We focus on microrefugia's ability to climatically disconnect from macroclimatic trends, examining temperature and Vapor Pressure Deficit (VPD) dynamics in microrefugia, adjacent control plots, and weather stations. Our study encompasses both "normal" conditions and heatwave episodes to explore the role of microrefugia as thermal and moisture insulators during extreme events. Landscape attributes such as relative elevation, solar radiation, distance to streams, and vegetation height are investigated for their contribution to short-term decoupling. Our results demonstrate that microrefugia exhibit notable decoupling from macroclimatic trends. This effect is maintained during heatwaves, underscoring microrefugia's vital role in responding to climatic extremes. Importantly, microrefugia maintain lower VPD levels than their surroundings outside and during heatwaves, potentially mitigating water stress for plants. This study advances our understanding of microclimate dynamics within microrefugia and underscores their ecological importance for plant persistence in a changing climate. As heatwaves become more frequent and severe, our findings provide insights into the role of microrefugia in buffering but also decoupling against extreme climatic events and, more generally, against climate warming. This knowledge emphasizes the need to detect and protect existing microrefugia, as they can be integrated into conservation strategies and climate change adaptation plans., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In the context of global warming, a clear understanding of microrefugia-microsites enabling the survival of species populations outside their main range limits-is crucial. Several studies have identified forcing factors that are thought to favor the existence of microrefugia. However, there is a lack of evidence to conclude whether, and to what extent, the climate encountered within existing microrefugia differs from the surrounding climate. To investigate this, we adopt a "bottom-up" approach, linking marginal disconnected populations to microclimate. We used the southernmost disconnected and abyssal populations of the circumboreal herbaceous plant Oxalis acetosella in Southern France to study whether populations in sites matching the definition of "microrefugia" occur in particularly favorable climatic conditions compared to neighboring control plots located at distances of between 50 to 100 m. Temperatures were recorded in putative microrefugia and in neighboring plots for approximately 2 years to quantify their thermal offsets. Vascular plant inventories were carried out to test whether plant communities also reflect microclimatic offsets. We found that current microclimatic dynamics are genuinely at stake in microrefugia. Microrefugia climates are systematically colder compared to those found in neighboring control plots. This pattern was more noticeable during the summer months. Abyssal populations showed stronger offsets compared to neighboring plots than the putative microrefugia occurring at higher altitudes. Plant communities demonstrate this strong spatial climatic variability, even at such a microscale approach, as species compositions systematically differed between the two plots, with species more adapted to colder and moister conditions in microrefugia compared to the surrounding area., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Trees play a key role in the structure and function of many ecosystems worldwide. In the Mediterranean Basin, forests cover approximately 22% of the total land area hosting a large number of endemics (46 species). Despite its particularities and vulnerability, the biodiversity of Mediterranean trees is not well known at the taxonomic, spatial, functional, and genetic levels required for conservation applications. The WOODIV database fills this gap by providing reliable occurrences, four functional traits (plant height, seed mass, wood density, and specific leaf area), and sequences from three DNA-regions (rbcL, matK, and trnH-psbA), together with modelled occurrences and a phylogeny for all 210 Euro-Mediterranean tree species. We compiled, homogenized, and verified occurrence data from sparse datasets and collated them on an INSPIRE-compliant 10 × 10 km grid. We also gathered functional trait and genetic data, filling existing gaps where possible. The WOODIV database can benefit macroecological studies in the fields of conservation, biogeography, and community ecology.