Natura 2000 priority habitat types of Greece face significant threats due to climate change. This study tests and demonstrates how distribution modelling predicts priority habitat types’ potential distribution, under various socio-economic scenario pathways extending to the year 2080, by employing MaxEnt species distribution modelling in order to capture habitat-wide climatic and anthropogenic dependencies. Across 10 priority habitat types in this study (10 out of the 18 found in Greece), model training outputs good-to-excellent predictive performance scores, which in turn reveal substantial heterogeneity in future range dynamics. By 2080, seven of the ten habitat types are projected to experience a suitable area contraction, with three (Wooded dunes with Pinus pinea and/or Pinus pinaster [2270], Species-rich Nardus grasslands, on siliceous substrates in mountain areas [6230], and (Sub-)Mediterranean pine forests with endemic blackpines [9530]) projected to lose >90% of suitable area, whereas the remaining types appear comparatively stable or show net expansion. Notably, 2270 is projected to lose all suitable area under all scenarios. Additionally, projected gains in suitability frequently occur far from current ranges and may fall partially outside present-day distributions, indicating potential spatial mismatch and management challenges. This study highlights the urgency for conservation management adapted to the needs of each habitat type in the frame of documented climate change impact, and provides a crucial tool for the implementation of biodiversity policies and strategies for mitigating the adverse effects of climate change on priority habitat types, from the local- to European- scale.

Description of spatial diversity patterns is a crucial part of biogeography and ecology. Diversity patterns vary with scale and the definition of the appropriate scale for their observation and analysis is not always straightforward depending on the research question and studied taxon. Species richness patterns are affected by the sampling design, as sampling area is a complex parameter defined by size, shape and spatial arrangement of the sample. We introduce the minimum area (minA) method, which estimates the smallest area containing a specific number of species. This approach uses species richness as the sampling’s independent variable, thus establishing a direct reference to the functional and ecological characteristics of the studied taxon. We examined how different abundance distributions, spatial aggregation, and starting point locations affect minA size with simulated communities and linear mixed-effects models. We applied the minA method to empirical data of African reptiles (Sauria, Serpentes, Amphisbaenia, Testudines) to explore its ability to identify diversity patterns and hotspots. The minA size decreases with species evenness and increases with spatial aggregation. The impact of the starting point's location on minA size is less important. In African reptiles, minA aligns with richness hotspots, but the minA patterns change with increasing number of species. This indicates that the underlying processes are taxon- and scale-specific. At small scales, environmental conditions and biotic interactions are more likely to drive local diversity. Αt larger scales, biogeographic history becomes the most influential factor. minA could be an alternative tool for studying α-diversity patterns and identifying species-rich regions.

The southwestern Balkans have an exceptional level of freshwater fish endemism, with the Ionian freshwater ecoregion recognized as a key biodiversity hotspot there. In this study, we examined how river Fish Assemblage Types (FATs), identified from 175 electrofished river sampling sites, shape the spatial patterns of β-diversity in this ecoregion. Initially, we used bipartite networks to identify areas of distinct fish assemblages. Subsequently, we used the Ružička index to estimate total β-diversity, decomposing it into the components of replacement and abundance differences. Local (LCBD) and species (SCBD) contributions to β-diversity were calculated. By applying generalized dissimilarity models and generalized additive models, we reveal which regional or local variables shape β-diversity and influence species important to the β–diversity patterns. Six distinct FATs were identified, each exhibiting high levels of β-diversity, but differing in the β-diversity component that contributed the most to the overall dissimilarity pattern. Geographic distance and temperature had the greatest influence on β-diversity, reflecting long-term geographical isolation or past connectivity among river basins, and a longitudinal river zonation pattern. The results provide insights into fish community and biophysical nuances that should be considered when building conservation strategies for this ecoregion. In the headwaters where rheophilic cold water species dominate, conservation actions should focus on protecting specific habitats and cool water conditions. In the middle and lowland areas, mixed methods should address both spatial replacement (endemic species) and abundance differences (widespread species). The findings of this study contribute to the identification of ecologically important water bodies and support conservation efforts by enhancing our understanding of spatial diversity patterns.

Climate and land use changes drive shifts in species distributions, causing variations in species richness. Yet the influence of shifts in species distributions on functional diversity at broad spatial scales remains uncertain. Here, we explored the potential effect of climate and land use changes on the functional diversity of European amphibian assemblages from the present to 2050, along with their effect on species richness. We performed species distribution modelling using a scenario of climate and land use change to estimate current and future potential distributions of 73 species. We estimated functional diversity using morphological and ecological functional traits. Our results highlight the intricate effects of climate and land use changes on taxonomic and functional diversity of amphibians. A climate-induced northward expansion of amphibians is anticipated, with temperature, precipitation, and forest cover prominently shaping future assemblages. Species expected to have shrinking ranges (n = 35) tend to mature sexually at a later age, produce fewer offspring per reproductive event, and live at higher maximum altitudes compared to species expected to expand (n = 38). Furthermore, trait composition changes are expected to exceed predictions based solely on species richness. These changes will vary geographically, with northern regions likely experiencing substantial increases in functional richness and functional redundancy, i.e., the coexistence of species with similar functional roles. Our findings underscore that functional diversity changes might serve as an early warning signal to assess human impacts on biodiversity.

Biological invasions are one of the main threats to biodiversity, but they also offer insights on different ecological processes, as highlighted by the hypotheses posited to explain the phenomenon. We explore the relative importance of different hypotheses using biotic (native diversity) and abiotic factors (climate and landscape configuration) as proxies driving the spatial pattern of alien plant biodiversity in Greece. The strongest predictor of alien species richness is native species richness. Landscape heterogeneity boosts this relationship, but native and alien species prefer different conditions. Landscape composition and configuration explain more of the variance of alien diversity than of native diversity, with native diversity increasing at more naturally vegetated areas and alien diversity at agricultural lands. Climate is associated more strongly with native diversity than with alien diversity, with native diversity increasing in colder regions and alien diversity in warmer regions. The transportation network was associated with higher alien species richness but not with native species richness, highlighting the importance of propagule/colonization pressure. These differences might indicate that aliens occupy part of the niche space that is not preferred by the natives and thus allow us to speculate on the role of limiting similarity as a driving force.

Aim We explored the range shifts of alien and native birds, the responses of alien and native beta-diversity to abiotic factors, and the effect of native diversity on alien beta-diversity in two time periods. Location Great Britain. Time period 1968-1972, 2007-2011. Taxa studied Breeding birds. Methods We estimated range shifts of alien and native species between the periods 1968-1972 and 2007-2011. Following, beta-diversity of alien and native communities was estimated by Jaccard pairwise index (beta(tot)) and partitioned into richness difference and replacement component for each period. We built abiotic generalized dissimilarity models including abiotic factors for alien and native beta(tot) and their components and a biotic model for aliens including native taxonomic and functional diversity as predictors. Results Most alien and half native species expanded into new regions during the 40-year period. The native species range shifts did not exhibit a clear pattern along the longitudinal or latitudinal gradient, while alien species tended to move north-westwards. The richness difference was the dominant component of alien beta-diversity, and the replacement component contributed mostly to native beta-diversity. Alien beta-diversity responded similarly but less strongly than native beta-diversity, to the abiotic gradients. Temperature-related variables, distance and precipitation were the most important abiotic drivers of native and alien beta-diversity. The biotic model of alien beta-diversity explained more deviance than the abiotic model. Main conclusions Alien species expanded into new regions over the 40 years, with alien beta-diversity driven mostly by species gains. The effect of environmental filtering on alien communities was weaker compared with native communities but was slightly reinforced in the second period compared with the first period, highlighting the role of environmental change in shaping diversity patterns. Native diversity played a key role in driving alien beta-diversity, through biotic interactions or/and by reflecting climatic suitability or niche availability for aliens.

The challenge of predicting the distribution of alien species has long been a focus of invasion ecology. Herein, we assessed biotic and abiotic factors from the 1980s as potential predictors of alien bird species patterns 20 years later in the state of New York. To assess the ability of each factor to predict future alien species patterns, we analysed the influence of biotic (native taxonomic, functional and phylogenetic diversity, and human population density) and abiotic (climate and land use) factors from the 1980s on the observed alien species richness patterns in the 2000s and the temporal change in the composition of the alien communities between the 1980s and the 2000s using both single-predictor and multivariate models. Alien species richness from the 1980s was a reliable predictor of the alien species richness and temporal beta-diversity patterns in the 2000s. Among abiotic factors, maximum temperature and agricultural land-uses constituted sufficient predictors of future alien species richness and better predictors than the native biotic factors. The performance of single-predictor models was generally weaker in predicting temporal alien beta-diversity; however, past alien species richness and maximum temperature again outperformed the other factors. Predictions and management decisions should focus on warm and agricultural areas, as well as areas with an already high number of established alien species.

Protecting global biodiversity is one of the most urgent tasks for the coming decades. Area-based conservation is a pillar for preserving ecosystems and species. Strictly protected areas specifically preserve biodiversity and ecosystem processes. The “EU Biodiversity Strategy for 2030” targets strict protection for 10% of land area. Here we performed the first analysis of strictly protected areas (as IUCN type Ia, Ib, and II) across Europe, by investigating their area coverage at the level of biogeographical regions, countries and elevation gradients. We show that, with few exceptions, the amount of strictly protected area is very limited and the spatial distribution of such protected areas is biased towards higher elevation sites, as in the case of other protected areas. Then, we suggest that potential areas should be identified to expand strictly protected areas with low economic and social costs including, for instance, areas with high biodiversity value, low population, and low productive land use. Finally, we propose that a coordinated effort and a strategic plan to achieve continental-scale conservation are fundamental, and at least half of this land under strict conservation (i.e. 5%) should be under the protection categories Ia and Ib.

Understanding the mechanisms of community assembly is of great importance to biogeography and ecology. Simultaneous investigation of the functional and phylogenetic facets of diversity has been proposed as a useful approach that allows inferences about such mechanisms. This study applies such an approach to explore diversity and structure within and among the main plant community types of mountainous forests in northern and central Greece. Functional and phylogenetic diversity and structure were measured in 25 community types of broadleaved deciduous and mountainous coniferous forests. Functional richness and Faith’s phylogenetic diversity were used to assess diversity, while mean pairwise functional and phylogenetic distances were used to investigate structure. Relationships between both facets of diversity and structure, as well as community types, were tested using boosted regression trees separately for all vascular plant taxa and taxa occurring in the forest understorey. Phylogenetic diversity was positively correlated with functional diversity, but phylogenetic structure was not a good predictor of functional structure. The understorey dataset revealed non-random structure for more vegetation plots than the dataset with all taxa. Habitat effects, represented by community types, were found to be better predictors of functional structure than phylogenetic structure, highlighting the need to account for habitat variability in studies of community assembly. In our study system, the two diversity facets provide complementary information on the structure of community types since most of the vegetation plots studied were found statistically significantly structured for one diversity facet (functionally clustered or phylogenetically overdispersed) and random for the other. Our results indicate that functional and phylogenetic measures provide different insights into the mechanisms driving the assembly of the forest community types studied.

Biodiversity promotes the functioning of ecosystems, and functional redundancy safeguards this functioning against environmental changes. However, what drives functional redundancy remains unclear. We analyzed taxonomic diversity, functional diversity (richness and β-diversity) and functional redundancy patterns of British butterflies. We explored the effect of temperature and landscape-related variables on richness and redundancy using generalized additive models, and on β-diversity using generalized dissimilarity models. The species richness-functional richness relationship was saturating, indicating functional redundancy in species-rich communities. Assemblages did not deviate from random expectations regarding functional richness. Temperature exerted a significant effect on all diversity aspects and on redundancy, with the latter relationship being unimodal. Landscape-related variables played a role in driving observed patterns. Although taxonomic and functional β-diversity were highly congruent, the model of taxonomic β-diversity explained more deviance than the model of functional β-diversity did. Species-rich butterfly assemblages exhibited functional redundancy. Climate- and landscape-related variables emerged as significant drivers of diversity and redundancy. Τaxonomic β-diversity was more strongly associated with the environmental gradient, while functional β-diversity was driven more strongly by stochasticity. Temperature promoted species richness and β-diversity, but warmer areas exhibited lower levels of functional redundancy. This might be related to the land uses prevailing in warmer areas (e.g., agricultural intensification).

The Biodiversity – Ecosystem Functioning (B–EF) relationship remains a topic of ongoing debate with most studies focusing on primary productivity, and documenting that this relationship takes many forms. It remains unclear if biodiversity drives productivity or productivity shapes biodiversity or the relationship is bidirectional. B-EF studies explore almost exclusively the relationship between species richness and ecosystem functioning, while the role of biotic interactions, a key component of ecosystem functioning, has been neglected. Here, using data of 80 local plant–pollinator networks on 20 Aegean islands, and of gross primary productivity (GPP) from the MODIS satellite, we explored the bidirectional relationship between interaction network structure (nestedness and specialization), species richness (plants and pollinators) and mean and inter-annual variability of GPP. We found that nestedness and specialisation of plant–pollinator networks is driven by mean GPP. However, specialisation alone was a significant predictor of mean GPP, implying that networks tend to be more specialised in low-productivity areas. Pollinator species richness exerted a strong effect on mean GPP with the remaining factors playing a minor role, while the effect of mean GPP on pollinator species richness was weaker. Furthermore, the nestedness of plant–pollinator networks drives inter-annual variability of GPP with more nested networks displaying less variability, which is in accordance with the predictions of the insurance hypothesis. Plant and pollinator species richness were also associated with inter-annual variability of GPP.

We studied the differentiation among plant communities of deciduous broadleaved and mountain coniferous forests in terms of functional diversity and identity at a regional scale (northern and central Greece). We asked if patterns of functional differentiation among communities are consistent between the overstorey and understorey layers and if they can be influenced by deep past environmental conditions. Functional Richness (FRic) and Functional Dispersion (FDis), as well as their standardized effect sizes, were employed to assess the multivariate functional diversity of the community types. In contrast, single-trait Community Weighted Means (CWMs) were used as surrogates of functional identity. The aforementioned indices were calculated for three datasets, namely all the vascular plant taxa found in individual vegetation plots (total community), all phanerophyte (tree and shrub) taxa (overstorey) and all non-phanerophyte vascular plant taxa (understorey). We found that community types and especially four broad forest types (beech, ravine, pine and oak forests) are well differentiated in terms of functional composition (identity), as indicated by Non-Metric Multidimensional Scaling (NMDS). After conducting an NMDS for the three datasets, functional identity based on the total floristic composition was found to be the best discriminator of the studied communities. However, contrasting patterns were found for some specific traits or their categories between overstorey and understorey layers. The patterns of functional diversity of the community types (based on multivariate indices), revealed by calculating the standardized effect sizes of FRic and FDis based on the richness null model, did not differ substantially from random expectations for most of the studied community types when the dataset of all the vascular plant taxa was analyzed. However, the patterns revealed for the overstorey layer differed from those for the understorey layer. For the latter layer, the clustered structure was revealed in many community types based on the ses.FDis metric. Indications of deep past influence on the functional composition were found for certain community types (i.e. ravine forests) based on single-trait metrics, but no indication of such influence was found based on multivariate indices. Our findings highlight the complementarity and the additive explanatory value of the simultaneous use of single- and multi-trait approaches and their application to different layers in forests.

The ongoing biodiversity crisis reinforces the urgent need to unravel diversity patterns and the underlying processes shaping them. Although taxonomic diversity has been extensively studied and is considered the common currency, simultaneously conserving other facets of diversity (e.g., functional diversity) is critical to ensure ecosystem functioning and the provision of ecosystem services. Here, we explored the effect of key climatic factors (temperature, precipitation, temperature seasonality, and precipitation seasonality) and factors reflecting human pressures (agricultural land, urban land, land-cover diversity, and human population density) on the functional diversity (functional richness and Rao's quadratic entropy) and species richness of amphibians (68 species), reptiles (107 species), and mammals (176 species) in Europe. We explored the relationship between different predictors and diversity metrics using generalized additive mixed model analysis, to capture non-linear relationships and to account for spatial autocorrelation. We found that at this broad continental spatial scale, climatic variables exerted a significant effect on the functional diversity and species richness of all taxa. On the other hand, variables reflecting human pressures contributed significantly in the models even though their explanatory power was lower compared to climatic variables. In most cases, functional richness and Rao's quadratic entropy responded similarly to climate and human pressures. In conclusion, climate is the most influential factor in shaping both the functional diversity and species richness patterns of amphibians, reptiles, and mammals in Europe. However, incorporating factors reflecting human pressures complementary to climate could be conducive to us understanding the drivers of functional diversity and richness patterns.

The EU Water Framework Directive foresees the ecological assessment of surface waters against identified pressures. Nutrient loading is the main pressure impairing the ecological quality of lake ecosystems, and aquatic macrophytes are considered good indicators of ecological response. In this study, we statistically assessed different aspects of aquatic plant (macrophyte) diversity in response to different trophic levels in Mediterranean lakes. We used 5690 relevés of aquatic vegetation, distributed over 305 transects, sampled in 18 freshwater lake ecosystems during 2013–2016. Our results show a significant decrease in taxonomic alpha diversity in lakes with a total phosphorus content above 100 μg/L. Syntaxonomic diversity followed the species richness pattern as well. Functional richness decreased along the trophic gradient, while functional dispersion was higher in lakes with high trophic levels. Taxonomic and functional beta partitioning presented changes in assembly processes leading to greater community homogeneity in lakes with higher trophic levels. In summary, we found no redundancy between taxonomic and functional diversity indices. These results provide novel insights into aquatic plant assembly processes of impacted freshwater lakes needed to forward conservation and restoration practices.

Biodiversity hotspots (BH) cover a small fraction of the Earth's surface, yet host numerous endemics. Human-induced biodiversity loss has been increasing worldwide, despite attempts to halt the extinction crisis. There is thus an urgent need to efficiently allocate the available conservation funds in an optimised conservation prioritization scheme. Identifying BH and endemism centres (EC) is therefore a valuable tool in conservation prioritization and planning. Even though Greece is one of the most plant species-rich European countries, few studies have dealt with the identification of BH or EC and none has ever incorporated phylogenetic information or extended to the national scale. Consequently, we are unaware of the extent that Special Areas of Conservation (SAC) of the Natura 2000 network efficiently protect Greek plant diversity. Here, we located for the first time at a national scale and in a phylogenetic framework, the areas serving as BH and EC, and assessed the effectiveness of the Greek SAC in safeguarding them. BH and EC are mainly located near mountainous areas, and in areas supposedly floristically impoverished, such as the central Aegean islands. A critical re-assessment of the Greek SAC might be needed to minimize the extinction risk of the Greek endemics, by focusing the conservation efforts also on the BH and EC that fall outside the established Greek SAC.

Phylogenetic diversity aims to quantify the evolutionary relatedness among the species comprising a community, using the phylogenetic tree as the metric of the evolutionary relationships. Could these measures unveil the evolutionary history of an area? For example, in a speciation hotspot (biodiversity cradle), we intuitively expect that the species in the community will be more phylogenetically clustered than randomly expected. Here, using a theoretical simulation model, we estimate the ability of phylogenetic metrics of current diversity to detect speciation history. We found that, in the absence of dispersal, if the incipient species do not coexist in the region of speciation (as expected under allopatric speciation), there was no clear phylogenetic clustering and phylogenetic diversity failed to detect speciation history. But if the incipient species coexisted (sympatric speciation), metrics such as standardized effect size of Faith’s Phylogenetic Diversity (PD) and of Mean Nearest Taxon Distance (MNTD) were able to identify areas of high speciation, while Mean Pairwise Distance (MPD) was a poor indicator. PD systematically outperformed MNTD. Dispersal was a game-changer. It allowed species to expand their range, colonize areas, and led to the coexistence of the incipient species originating from a common ancestor. If speciation gradient was spatially contiguous, dispersal strengthened the associations between phylogenetic clustering and speciation history. In the case of spatially random speciation, dispersal blurred the signal with phylogenetic clustering occurring in areas of low or no speciation. Our results imply that phylogenetic clustering is an indicator of speciation history only under certain conditions.

Assessing spatial and temporal patterns of biodiversity change is essential to understand how communities vary over time and confront to environmental changes for the resilience of ecosystem functioning. We use data from two bird atlases of Britain collected during the breeding periods 1988-1991 and 2008-2011 to measure temporal beta-diversity of taxonomic, functional and phylogenetic dimensions and examine the relationship and the level of congruence of the three dimensions of temporal beta-diversity and their respective partitioned components (turnover-nestedness). Temporal beta-diversity, turnover and nestedness patterns were highly congruent for the taxonomic and phylogenetic dimension, although these dimensions were weakly associated with the functional dimension. We found higher levels of temporal changes for the taxonomic (mean Jaccard beta-diversity 0.27) and phylogenetic (mean Jaccard beta-diversity 0.21) dimensions than for the functional dimension (mean Jaccard beta-diversity 0.09), implying that despite the changes in species composition the functional composition of the communities remained less affected. For taxonomic and phylogenetic dimensions, turnover contributed more than nestedness to shaping beta-diversity, while for functional beta-diversity the two components contributed similarly. Communities at higher altitudes were also more functionally similar in 20 years but with more changes in taxonomic and phylogenetic diversity possibly due to environmental filtering. We hypothesize that the low congruence might be due to species with extreme trait values persisting throughout time and retaining the volume of functional space and thus contributing to the low temporal change of functional diversity despite the high levels of change in species composition, perhaps an indication of functional "stability."

Native-alien species relationship is one of the potential mechanisms to explain alien species' success. Most approaches have so far focused on species richness, but species-centric approaches alone are of limited explanatory ability. We utilized the breeding bird atlases of Great Britain at three time points, to examine the temporal patterns of alien bird species assemblages' richness and composition and analyze the spatio-temporal relationship between them and native species functional and phylogenetic diversity. Alien birds were successful in increasing their average local richness and range from the 1970s to the 2010s, without high values of the replacement component of β-diversity in most assemblages and with increasing richness in the majority of atlas cells. Communities with higher native diversity were positively associated with higher alien species richness and overall, our results showed that native biodiversity metrics can act as reliable predictors of alien species richness patterns. Native phylogenetic diversity emerged as an important predictor of alien species richness, whereas functional diversity was not as successful. Phylogenetic diversity may have captured native species' functional differences more effectively and/or the added layer of phylogenetic information increased phylogenetic diversity's ability to predict alien species richness patterns and may be indicative of evolutionary processes reflecting the mechanisms shaping native-alien species' relationship. If we were to predict where these alien birds may spread within the next 20 years, our results point to phylogenetically rich communities. This is likely a reflection of habitat heterogeneity and/or resource availability in these communities. In any case, a multifaceted approach is preferable, as different measures highlight different mechanisms driving communities' invasibility.

Europe’s Natura 2000 network (N2K), based on the EU Birds and Habitat Directives, has rapidly expanded protected areas targeting species and habitat types. In Greece, 52.4% of native freshwater fish are considered as species of EU community interest within the Habitats Directive (HD). However, 31.3% of all threatened fish species at a global level and 32.0% at a national level, are not included in the Habitat Directives Annex lists. Fishes in Greece’s rivers are understudied, precise knowledge of their distributions is poor for most species. We utilize a large set of site-based electrofishing samples to explore the coverage of these species by the country’s Natura 2000 sites. Field surveys recorded 102 species inhabiting rivers within 645 sampling sites. Although the majority of the HD listed, threatened and endemic freshwater fish species exist within the current N2K network, important gaps are evident and four HD species were not found within any Natura 2000 sites. In analyzing fish densities from field sampling, only two upland-stream species, Salmo farioides and Barbus strumicae, show significantly higher abundance inside N2K sites. Applying a Combined Index utilizing IUCN vulnerability status, species rarity and richness, we identified 161 hotspot sites for riverine fishes; 50.9 % of all hotspots are located outside of N2K network, especially in lowland areas. Unprotected areas with a high concentration of hotspots are mapped; the river basins with the highest number of such unprotected hotspots belong to the Strymonas, Pinios, Evrotas and Aoos rivers. With concern for the EU’s revised biodiversity conservation strategy, our screening level assessment provides insights for unmet conservation needs and the method is readily transferable to other states and protected area jurisdictions.