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We present a checklist of spiders inhabiting the Pelagie archipelago and Pantelleria island, in the Strait of Sicily (Southern Italy). Data were compiled from both literature sources and unpublished materials stored in museum collections. In total, we report new data on 100 species, bringing the total number of species documented for the islands of the Strait of Sicily to 148. Among these, 8 are new for Europe and 9 new for Italy. The island of Lampedusa hosts the highest number of species (107), followed by Pantelleria (63) and Linosa (25). The most represented families are Gnaphosidae in Lampedusa and Linosa, while Salticidae is dominant in Pantelleria. Most of the species present on the islands of the Strait of Sicily have a Holarctic distribution. Several rare species are recorded, including Haplodrassus crassipes (Lucas, 1846), Palliduphantes labilis (Simon, 1913) and Xysticus promiscuus O. Pickard-Cambridge, 1876. In addition, the female of Poecilochroa loricata Kritscher, 1996 (Gnaphosidae) is here described and illustrated for the first time. As revealed by the study of the species-area relationship, the islands of the Strait of Sicily host a higher number of species compared to other small islands in Italy. Accordingly, species richness recorded in Lampedusa and Linosa is higher than expected, while further investigations are suggested to increase knowledge of the local spider diversity. [ABSTRACT FROM AUTHOR]

Summary: Relationships between crop genetic and functional diversity are key to addressing contemporary agricultural challenges. Yet, there are few approaches for quantifying the relationship between genetic diversity and crop functional trait expression. Here, we introduce 'functional space accumulation curves' to analyze how trait space increases with the number of crop genotypes within a species.We explore the potential for functional space accumulating curves to quantify genotype–trait space relationships in four common annual crop species: barley (Hordeum vulgare), rice (Oryza sativa), soybean (Glycine max), and durum wheat (Triticum durum). We also employ these curves to describe genotype–trait space relationships in the wild annual Arabidopsis thaliana, which has not been subjected to artificial selection.All five species exhibited asymptotic functional space accumulation curves, suggesting a limit to intraspecific functional crop diversity, likely due to: dominant phenotypes represented by several genotypes; or functional redundancy that might exist among genotypes. Our findings indicate that there is a diminishing return of functional diversity with increasing number of genotypes.Our analysis demonstrates the efficacy of functional space accumulation curves in quantifying trait space occupancy of crops, with implications for managing crop diversity in agroecosystems, and genetic diversity in crop breeding programs. [ABSTRACT FROM AUTHOR]

The island biogeography theory predicts that species richness in islands and island-like systems is the ultimate result of island isolation and area. Species with high dispersal capabilities are predicted to be less affected by these factors because of their capacity to move more efficiently between islands or habitats, and here we test this idea in bats, the only mammals capable of flight. We conducted mist net and acoustic surveys across 21 islands in the San Juan Archipelago (Washington State, United States) and adjacent northwest mainland to: (i) investigate the effects of island area, distance from mainland, and habitat on bat diversity; and (ii) evaluate whether differences in morphological (body mass, forearm length, wing loading) and ecological (dietary niche breadth, foraging guild) traits among species influence their prevalence across islands. We found that island size strongly influenced patterns of species richness, with larger islands having a greater number of bat species. However, neither island distance from mainland nor any measure of habitat availability was a significant predictor of species richness at the scale of this study. Additionally, we found that dietary niche breadth, as opposed to any morphological trait, best predicted the prevalence of species across the islands. Our results suggest that species with more specialized diets may be more vulnerable to habitat fragmentation, and provide insight into how geographic and ecological factors affect the diversity of insular bat communities, adding to growing knowledge about the role of species traits as mediators of their responses to large-scale landscape structure. [ABSTRACT FROM AUTHOR]

We present a checklist of spiders inhabiting the Pelagie archipelago and Pantelleria island, in the Strait of Sicily (Southern Italy). Data were compiled from both literature sources and unpublished materials stored in museum collections. In total, we report new data on 100 species, bringing the total number of species documented for the islands of the Strait of Sicily to 148. Among these, 8 are new for Europe and 9 new for Italy. The island of Lampedusa hosts the highest number of species (107), followed by Pantelleria (63) and Linosa (25). The most represented families are Gnaphosidae in Lampedusa and Linosa, while Salticidae is dominant in Pantelleria. Most of the species present on the islands of the Strait of Sicily have a Holarctic distribution. Several rare species are recorded, including Haplodrassus crassipes (Lucas, 1846), Palliduphantes labilis (Simon, 1913) and Xysticus promiscuus O. Pickard-Cambridge, 1876. In addition, the female of Poecilochroa loricata Kritscher, 1996 (Gnaphosidae) is here described and illustrated for the first time. As revealed by the study of the species-area relationship, the islands of the Strait of Sicily host a higher number of species compared to other small islands in Italy. Accordingly, species richness recorded in Lampedusa and Linosa is higher than expected, while further investigations are suggested to increase knowledge of the local spider diversity.

Thermo-mineral springs are specific ecosystems with extreme environmental conditions that constitute interesting models for studying metacommunity processes. Since these springs can be considered as islands within a terrestrial context, we first aimed to test some predictions of the theory of island biogeography and the distance-decay hypothesis on benthic diatom communities. Then, we aimed to quantify the influence of physical, chemical, climatic and spatial factors on species assemblages. We evaluated the species-area relationship for all springs and for several group of springs classified according to their environmental and hydrochemical composition. The influence of environmental variables on α-diversity was tested. We also investigated whether β-diversity was related to spring isolation or changes in environmental conditions. Finally, we determined the importance of environmental and spatial variables in shaping diatom communities using ordination and variation partitioning. We did not find any species-area relationship whatever the group of springs investigated, and no geographical distance-decay pattern was observed. We found a significant effect of physical and chemical parameters on α-diversity and composition. Thus, diatoms communities of thermo-mineral springs did not seem to be influenced by dispersal processes at the scale of our study but appeared to be patterned by physical and chemical factors. [ABSTRACT FROM AUTHOR]

Invasive alien plants (IAPs) pose a significant threat to island biodiversity and severely impact ecosystems. Understanding the species–area relationship and environmental determinants of growth forms for IAP species on subtropical islands is crucial for establishing an IAP's early warning mechanism, enhancing island ecological management, and protecting the ecosystems of Fujian and other subtropical islands. The study identified significant species–area relationships for IAPs and different life-form plants (trees, shrubs, and herbs), with slopes of 0.27, 0.16, 0.15, and 0.24, respectively. The small island effect does not apply to all species. Isolation has little effect on species richness, and the IAPs on Fujian islands do not conform to the isolation effect in island biogeography. Landscape factors are the main determinants of IAPs and different life-form species richness, with area, shape index, and perimeter–area ratio being the three primary landscape factors. These environmental factors are closely related to habitat heterogeneity. Besides landscape factors, different life forms respond differently to environmental factors. Climate drives the species richness distribution of shrubs and herbs, while trees are mainly influenced by human activities. Overall, landscape, human disturbance, and climate jointly drive the distribution of IAPs, with landscape factors being the most significant. [ABSTRACT FROM AUTHOR]

Increases in species richness with habitat area (species–area relationship, or SAR) and increases in ecosystem function with species richness (biodiversity–ecosystem functioning, or BEF) are widely studied ecological patterns. Incorporating functional trait analysis into assemblage datasets may help clarify interpretations of SAR and BEF relationships in natural ecological systems. For example, life history theory can be used to make predictions about what species are most important in generating ecosystem function given a certain set of environmental conditions. We used quantitative assemblage data for freshwater mussels at nine sites in western Alabama, USA, to test for SAR and BEF relationships. At each site, we calculated species richness, mussel assemblage density, and two fundamental metrics of ecosystem function: biomass and secondary production. We also tested whether the proportional biomass and production contributions from species belonging to each of three life history strategies—opportunistic strategists adapted to unstable or frequently disturbed habitats, periodic strategists adapted to habitats subject to predictable large‐scale disturbances, and equilibrium strategists adapted to stable habitats—varied longitudinally with stream drainage area, a proxy for habitat area. Species richness increased with stream size (SAR), and both biomass and production increased with species richness (BEF) and mussel density. There were few longitudinal changes in the proportional contributions of the different life history strategy classifications that we used, but the invasive clam Corbicula fluminea contributed proportionally more biomass and production at sites that had smaller drainage areas. This study provides further evidence for a clear longitudinal SAR in stream‐dwelling taxa. It also suggests BEF relationships for biomass and secondary production in natural assemblages but underscores the importance of assemblage density in BEF studies that use observational field data. Variation in proportional biomass and production contributions by different life history strategies was likely limited by the size of the stream size gradient in our study, as contributions were uniformly high for species with life history traits better adapted to stable and productive habitats such as mid‐sized rivers with low or predictable hydrologic disturbance frequencies. This highlights the need to understand how organisms' functional traits govern their relationships to the environment at different scales. [ABSTRACT FROM AUTHOR]

Deforestation is a major type of land use change to accommodate growing population, especially in developing countries. The risk of diversity loss due to habitat loss can be estimated using the species-area relationship based on abundance of each species. However, deforestation often occurs before there is any understanding of the impact of deforestation on tree diversity. Here, we assessed the potential effect of forest habitat destruction on the loss of species richness in a mature subtropical broadleaf forest in central China. We surveyed and constructed the species-area relationship for 54 400 m2 plots, and simulated habitat loss scenarios by randomly and aggregately sampling plots. Rank-abundance of the 21 tree species was best fitted by the Zipf-Mandelbrot model, and our sample size was sufficient by the criterion of Hill numbers at orders q = 0, 1, and 2. We found that the number of species lost due to habitat loss was well predicted by the random placement species loss-area loss curve, and was lower than that due to aggregated habitat destruction by less than one species. The probability of losing one species reached 40% when losing 16 plots by aggregated sampling, 10 plots fewer than that by random sampling. Moreover, the probability of losing two species was 10–22 % higher by aggregately sampling than that by randomly sampling when losing 17 – 34 plots (0.68 – 1.36 ha). Considering that aggregated deforestation is common in reality, the results imply that the number of tree species lost due to deforestation could be higher than the theoretical estimation. Our study suggests the importance of assessing the impact of deforestation on tree diversity before selective logging in subtropical forests.

Species–area models now frequently include habitat heterogeneity. These models often fit real-world data better than those that exclude this factor. However, such models usually link the effects of habitat heterogeneity and study area. Critically, we show that difficulties in quantifying habitat heterogeneity within these models can lead to distortions of the apparent effect of area on species richness. Here, we derive a model that minimises these distortions by partitioning the influence of habitat heterogeneity from that of area, without compromising ease of application. This ‘jigsaw model’ achieves this by assuming that different habitats within an area can support similar numbers of species. We compare the behaviour of this model to that of existing models of similar complexity using both simulated island ecosystems and 40 published empirical datasets. The effects of habitat heterogeneity and area on species richness vary independently in our simulations, and these independent effects are recovered by the jigsaw model. This flexibility, however, is not present when the same data are analysed using other models of similar complexity. When applied to real-world data, the jigsaw model demonstrates that the relative importance of area and habitat heterogeneity varies depending on the study system. The jigsaw model provides the best fit to real-world data (according to AICc) of all tested models in logarithmic form, and the second best fit, after the choros model, in power-law form. Our results demonstrate the importance of partitioning the effects of habitat heterogeneity and area on species richness in biogeographic models. The jigsaw model is a simple but powerful tool for such partitioning. It has the potential to elucidate the underlying drivers of species richness patterns, and to be used as a tool in biological conservation projects, where data are often incomplete.

Biological invasions are among the threats to global biodiversity and social sustainability, especially on islands. Identifying the threshold of area at which non-native species begin to increase abruptly is crucial for early prevention strategies. The small-island effect (SIE) was proposed to quantify the nonlinear relationship between native species richness and area but has not yet been applied to non-native species and thus to predict the key breakpoints at which established non-native species start to increase rapidly. Based on an extensive global dataset, including 769 species of non-native birds, mammals, amphibians and reptiles established on 4277 islands across 54 archipelagos, we detected a high prevalence of SIEs across 66.7% of archipelagos. Approximately 50% of islands have reached the threshold area and thus may be undergoing a rapid increase in biological invasions. SIEs were more likely to occur in those archipelagos with more non-native species introduction events, more established historical non-native species, lower habitat diversity and larger archipelago area range. Our findings may have important implications not only for targeted surveillance of biological invasions on global islands but also for predicting the responses of both non-native and native species to ongoing habitat fragmentation under sustained land-use modification and climate change. [ABSTRACT FROM AUTHOR]

Simple Summary: This study investigates the species–area relationship of amphibians on the Zhoushan Archipelago using eDNA metabarcoding. By analyzing amphibian species diversity on the Zhoushan Archipelago, the eDNA metabarcoding detected eight amphibian species on the islands and nine species in the mainland areas. Findings reveal that the amphibian species diversity is positively related to the island area. In comparison with the traditional line transect method, eDNA metabarcoding detected more amphibian species. eDNA showcases enormous potential in detecting amphibian species. The species–area relationship is important for understanding species diversity patterns at spatial scales, but few studies have examined the relationship using environmental DNA (eDNA) techniques. We investigated amphibian diversity on 21 islands of the Zhoushan Archipelago and nearby mainland areas in China using the combination of eDNA metabarcoding and the traditional line transect method (TLTM) and identified the species–area relationship for amphibians on the islands. The mean detection probability of eDNA is 0.54, while the mean detection probability of TLTM is 0.24. The eDNA metabarcoding detected eight amphibian species on the islands and nine species in the mainland areas, compared with seven species on the islands and nine species in the mainland areas that were identified by TLTM. Amphibian richness on the islands increased with island area and habitat diversity. The species–area relationship for amphibians in the archipelago was formulated as the power function (S = 0.47A0.21) or exponential function (S = 2.59 + 2.41 (logA)). Our results suggested that eDNA metabarcoding is more sensitive for the detection of amphibian species. The combined use of eDNA metabarcoding and the traditional line transect method may optimize the survey results for amphibians. [ABSTRACT FROM AUTHOR]

Aim: Species–area relationships (SAR) are widely utilized for estimating the species richness and its spatial turnover across various scales. Despite the prevalent characterization of SAR using the power law in many microbial community studies, its efficacy remains unvalidated. This study aims to characterize the microbial SAR and its mechanisms in alpine grassland soils on the Qinghai‐Tibet Plateau (QTP). Location: Qinghai‐Tibet Plateau, China. Time Period: August 2014. Major Taxa Studied: Soil bacteria. Methods: Soil samples were collected from five alpine grassland sites on the QTP. Employing a nested sampling strategy at each site, soil samples were collected in plot sizes ranging from 0.5 × 0.5 m2 to 2048 × 2048 m2. Soil bacterial communities were analysed by sequencing 16S ribosomal RNA gene amplicons using an Illumina MiSeq. Results: The bacterial SAR exhibited a logarithmic power law (R2: 0.952–0.999), outperforming the power law (R2: 0.701–0.852). Consequently, the most widely adopted power law led to an overestimation of species richness by up to 15.07% in areas >256 × 256 m2, and the regional maximum theoretical richness based on Chao1 by up to 9.88%. Mechanistically, the passive sampling hypothesis was refuted through the rarefied species richness analysis, and the disproportionate effect hypothesis was rejected based on analyses of the effective numbers of species number conversions for the probability of interspecific encounters (SPIE). Notably, Pearson and multiple linear regression analyses indicated that the spatial turnover of bacterial richness was determined by the environmental heterogeneity (R2: 0.855–0.999), rather or better than environmental variables themselves, supporting the 'environment heterogeneity hypothesis'. Main Conclusions: Soil bacterial SAR in alpine grasslands exhibited a logarithmic power relationship. Spatial turnover was primarily governed by the environmental heterogeneity. In contrast, the traditional power law leads to an overestimation of soil bacterial diversity at the regional scale. [ABSTRACT FROM AUTHOR]

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Questions: Grasslands provide important provisioning services worldwide and their management has consequences for these services. Management intensification is a widespread land‐use change and has accelerated across North America to meet rising demands on productivity, yet its impact on the relationship between plant diversity and productivity is still unclear. Here, we investigated the relationship between plant diversity and grassland productivity across nine ecoclimatic domains of the continental United States. We also tested the effect of management intensification on diversity and productivity in four case studies. Methods: We acquired remotely sensed gross primary productivity data (GPP, 1986–2018) and plant diversity data measured at different spatial scales (1, 10, 100, 400 m2), as well as climate variables including the Palmer drought index from two ecological networks. We used general linear mixed models to relate GPP to plant diversity across sites. For the case study analysis, we used linear mixed models to relate plant diversity to management intensity, and tested if the management intensity influenced the relationship between GPP (mean and temporal variation) and drought. Results: Across all sites, we observed positive relationships among species richness, productivity, and the temporal stability of mean annual biomass production. These relationships were not affected by the scale at which species richness was observed. In three out of the four case studies, we observed that management effects on species richness were only significant at broader scales (i.e., ≥10 m2) with no clear effect found at the commonly used 1‐m2 quadrat scale. In one case study, species‐poor, intensively managed pastures presented the highest productivity but were more sensitive to dry conditions than less intensified pastures. However, in other case studies, we did not observe significant effects of management intensity on the magnitude or stability of productivity. Conclusions: Generalization across studies may be difficult and require the development of intensification indices general enough to be applied across diverse management strategies in grazilands. Understanding how management intensification affects grassland productivity will inform the development of sustainable intensification strategies. [ABSTRACT FROM AUTHOR]

Aim: The small‐island effect (SIE) describes an anomalous feature of the species–area relationship (SAR) on smaller compared to larger islands. However, previous studies on SIEs mainly focused on taxonomic diversity and overlooked phylogenetic and functional diversity. In this study, we explored SIEs in three dimensions of diversity. We expect to see the non‐linear thresholds in the effect of area on three dimensions of diversity as well as on community structures, because the dominant assembly processes vary across spatial scales. Location: The West Indies. Taxon: Herpetofauna. Methods: We derived data on the presence/absence of 199 amphibian species on 163 islands and 614 reptile species on 748 islands in the West Indies. We built a species‐level phylogenetic tree and a species‐level functional tree to estimate six taxonomic, phylogenetic and functional diversity indices. Four community metrics on behalf of the phylogenetic and functional community structure of each island were calculated using a null modelling framework and was quantified using the standardized effect size (SES). We explored the non‐linear thresholds in the effect of area for each of the diversity indices and SES values of community metrics by comparing six piecewise regression models with a linear regression model and a null model. Results: We found evidence of SIEs in four diversity indices representing all three dimensions of diversity. Besides, area thresholds were also found in the phylogenetic and functional community structure for both amphibians and reptiles. Random extinction, competitive exclusion and adaptive radiation are the dominant processes structuring reptile communities on small, intermediate and large islands respectively. Main Conclusions: To conduct a comprehensive biodiversity conservation plan concerning taxonomic, phylogenetic and functional diversity, we suggest it is necessary to explore the SIEs in various diversity indices representing all three dimensions of diversity and apply the lowest threshold value to make management strategies. [ABSTRACT FROM AUTHOR]

Small islands represent a common feature in the Mediterranean and host a significant fraction of its biodiversity. However, the distribution of plant species richness across spatial scales—from local communities (alpha) to whole islands (gamma)—is largely unknown, and so is the influence of environmental, geographical, and topographical factors. By building upon classic biogeographic theory, we used the species–area relationship and about 4500 vegetation plots in 54 Central Mediterranean small islands to identify hotspots of plant species richness and the underlying spatial determinants across scales. To do so, we fitted and averaged eight species–area models on gamma and alpha richness against island area and plot size, respectively. Based on positive deviations from the fitted curves, we identified 12 islands as cross‐scale hotspots. These islands encompassed around 70% of species and habitat richness, as well as almost 50% of the rarest species in the data set, while occupying less than 40% of the total island surface. By fitting generalized linear mixed models, we found that gamma richness was mainly explained by island area and was weakly related to mean annual temperature (positively) and annual precipitation (negatively). As for alpha richness, after accounting for the idiosyncratic effect of habitats and islands, plot size and gamma richness remained the only significant predictors, showing a positive relationship. This work contributes to the understanding of the patterns and drivers of plant diversity in Central Mediterranean small islands and outlines a useful methodology for the prioritization of conservation efforts. [ABSTRACT FROM AUTHOR]

Temporal biodiversity change involves colonization, extinction, and recurrence of species. These processes vary with spatial grain (i.e. the area at which biodiversity is assessed), but there is little theory to explain this. Here, we present theoretical scenarios showing that colonization, extinction, and recurrence of species can either increase or decrease in strength across grain size. We tested for these patterns in empirical data on Czech birds over 30 years, and several orders of magnitude of spatial grain. We found that colonization increased from local to national scales, while extinctions followed a hump‐shaped pattern, leading to a higher temporal increase of richness towards coarse grains. Probabilities of colonization and extinction decreased with grain size, with a steeper decrease for extinction. Our results hold independently across two time periods (1985–2002 and 2002–2017), and colonization is the dominant process behind temporal change of richness. This decomposition of biodiversity change allowed us to identify scale‐wise ecological mechanisms driving biodiversity change, and explain seemingly confusing directions of biodiversity change at different spatial scales. [ABSTRACT FROM AUTHOR]

Species richness is a fundamental property of biodiversity patterns and is properly expressed by the species–area relationship (SAR), namely the increase in the number of species with the area. Here, we studied and explored the species–area relationship with respect to vascular plant species in Italy and compared vascular plant richness among Italian administrative regions. Concerning the entire vascular flora (native and alien), the best-performing formula is the Arrhenius' Power function: S = c Az. The constants of this function are c = 241.2 and z = 0.281. The best-performing formula concerning just native (c = 245.2 and z = 0.263) and alien (c = 10.1 and z = 0.404) richness is the Power function as well. The floristically richest Italian regions considering the entire flora are Liguria, Friuli Venezia Giulia, and Trentino-Alto Adige, which are also the regions that are richest in alien flora unfortunately. Regions of particular naturalistic interest are Abruzzo, Valle d'Aosta, and Molise, because only these three regions exhibit native floristic richness that is higher than expected, and this is coupled with an alien floristic richness that is lower than expected. On the contrary, four regions (Lombardia, Veneto, Toscana, and Emilia-Romagna) show potentially severe conservation problems due to biological invasions since they experience native floristic richness that is lower than expected, with an alien floristic richness that is higher than expected. This study offers for the first time the 'c' and 'z' constants specifically calibrated at the national level for Italian vascular flora. The availability of such constants allows the calculation of the number of expected species for a given area to be investigated, providing a robust starting hypothesis for floristic studies. [ABSTRACT FROM AUTHOR]

Mediterranean- and tropical-climate regions harbour the richest regional-scale floras globally. Until recently, however, comparisons of their diversities have been hindered by a lack of comprehensive inventories of tropical floras. Using taxonomically verified floras, we analyse area-adjusted plant diversities of five Mediterranean- and 35 tropical-climate regions to determine which are the most species-rich regions on Earth. On average, the Neotropics and tropical Southeast Asia support the most diverse floras globally. However, the area-adjusted diversities of the richest floras in these tropical regions are matched by those of two Mediterranean-climate floras, namely the Cape (second richest) and Mediterranean Basin (sixth richest). Except for Madagascar and Burundi, the Afrotropical regions were substantially less diverse than other tropical floras and half of the Afrotropical floras were poorer than the least diverse Mediterranean-climate region, namely Central Chile. We evaluate the likely ecological and evolutionary drivers of these plant diversity patterns in terms of three hypotheses that are apposite for global scale comparisons, namely water-energy dynamics, biome stability, and ecological heterogeneity. Water-energy dynamics appear to have little influence in explaining these diversity patterns: nodes of high global plant diversity are associated with climates that support year-round plant production (tropical climates) and those where the growing season is constrained by a winter rainfall regime (Mediterranean-type climates). Moreover, while the Afrotropics have higher primary production than the Neotropics and Southeast Asian tropics, they have markedly lower plant diversity. Instead, these patterns appear to be consistent with the hypothesis that the synergy of historical biome stability (reducing extinction rates) and high ecological heterogeneity (promoting speciation rates) better explain global patterns of regional-scale plant diversity.

Invasive alien plants (IAPs) pose a significant threat to island biodiversity and severely impact ecosystems. Understanding the species–area relationship and environmental determinants of growth forms for IAP species on subtropical islands is crucial for establishing an IAP’s early warning mechanism, enhancing island ecological management, and protecting the ecosystems of Fujian and other subtropical islands. The study identified significant species–area relationships for IAPs and different life-form plants (trees, shrubs, and herbs), with slopes of 0.27, 0.16, 0.15, and 0.24, respectively. The small island effect does not apply to all species. Isolation has little effect on species richness, and the IAPs on Fujian islands do not conform to the isolation effect in island biogeography. Landscape factors are the main determinants of IAPs and different life-form species richness, with area, shape index, and perimeter–area ratio being the three primary landscape factors. These environmental factors are closely related to habitat heterogeneity. Besides landscape factors, different life forms respond differently to environmental factors. Climate drives the species richness distribution of shrubs and herbs, while trees are mainly influenced by human activities. Overall, landscape, human disturbance, and climate jointly drive the distribution of IAPs, with landscape factors being the most significant.

1. Nitrogen (N) enrichment often decreases plant species richness in local communities, thus altering plant species–area relationships (SAR). However, whether N enrichment affects the SAR across global grasslands has not yet been well explored. Additionally, whether and how seasonal N enrichment alters the SAR remains unknown.2. This study employed data from global grasslands (meta-analysis) in combination with a seasonal field N addition experiment during the first 6 consecutive years (2014–2020) in a temperate grassland in northern China.3. We found that N addition did not alter the SAR slopes across global grasslands and our experimental grassland, but significantly reduced the intercepts (plant species richness at the 1 m2 plot scale). There was no significant difference among seasonal N treatments. The SAR intercepts were negatively correlated with increasing experimental years in our temperate grassland, without significant differences among the three seasonal N addition treatments, indicating a cumulative effect on the reduction in plant species richness at 1 m2 with N-enriched conditions.4. These results suggest that N enrichment affects the SAR in grassland ecosystems by reducing the SAR intercepts. Therefore, biodiversity conservation activities should be applied urgently in localities facing increasing atmospheric N deposition.

Context: Extinction debt, the time-delayed species loss response to fragmentation associated with habitat clearance, is a conservation concern for management of biological diversity globally. Extinction debt is well defined but difficult to measure owing to the long-term data needed to measure species loss, particularly for communities of long-lived species. Aims: We aimed to estimate extinction debt for two adjacent threatened communities with contrasting soil fertility in south-western Australia: banksia and tuart woodlands. Further, we assessed what species functional traits are associated with extinction risk. Methods: Using contemporary (2016) and historical (1992) data on vegetation richness, and patch characteristics dating back to the time of European colonisation (1829), we examined 60 woodland patches using three methods to detect and quantify extinction debt. Key results: We found evidence of extinction debt in banksia woodland, but not in tuart woodland. We estimated the extinction debt for banksia woodlands as a future average loss of 28% or ~13 species per patch. Conclusions: Our study demonstrated a delay of species loss consistent with extinction debt in one of two vegetation communities. Despite sharing species and traits, these vegetation communities have responded differently to landscape change over the same timescale and within the same landscape. Implications: Understanding how vegetation communities, and functional trait types, respond to time-delayed impacts helps land managers to prioritise intervention efforts to pre-empt species decline and extinction through species conservation, and ecological restoration of remnant vegetation patches. Time-delayed species loss in response to fragmentation associated with habitat clearance, is a conservation concern for management of biological diversity in the world's fragmented landscapes. We found evidence of future species loss in some of the study communities. Banksia woodlands had 28% average loss (13 species per patch). Understanding how different community types respond to time-delayed impacts helps land managers to prioritise intervention efforts to pre-empt species decline and eventual extinction through conservation, management and restoration of remnant vegetation patches. BT22134_toc.jpg [ABSTRACT FROM AUTHOR]

Islands occupy a proportionately small area on Earth, however they play a crucial role in Ecology and Biogeography, as they constitute “natural laboratories”. The increased number of species, with increasing island area, is such a commonly observed pattern that it has been labelled as one of the few laws of ecology. The Aegean archipelago is of broad biogeographical interest, as it has a considerable number of islands in addition to a rich paleogeographical and geological history, while being divided among three continents (Europe, Asia, Africa). As a result, the composition of life in the Aegean is dominated by species of European, Asian, African origin as well as species endemic in the archipelago. In this framework, we approached the species–area relationship (SAR) of the Aegean islands for six different organismic groups (birds, herptiles, snails, isopods, tenebrionids and chilopods) and 20 different models. The aim was to determine which model(s) perform better for each taxon and also to compare the z and C parameters of the power model between animal groups, which are the only model parameters to date that have been linked with biological processes. We compared the relationship across different taxa for the entire archipelago and for the exact same islands, in two subgroups with similar paleogeographic history and environmental conditions in the central and eastern Aegean. For the taxonomic groups that were examined a strong correlation between the number of species and area was found, except for chilopods and herptiles. Although there is no universal best model for the SAR of the Aegean, the power model performed better for invertebrates, whereas concerning vertebrates there was more ambiguity in the shape of the relationship.

An increasing number of studies have focused on identifying thresholds in the species–area relationship (SAR). The most common approach in such studies is to use piecewise regression models. While a few software packages are available for fitting piecewise models, these resources are general regression packages (i.e., they are not specifically designed for the analysis of SAR data) and tend to only provide functions for fitting a subset of the piecewise models proposed in the SAR literature. Given the large number of SAR studies now fitting piecewise models, there is a need for a software package that provides functions for fitting a range of piecewise models, including continuous, left-horizontal and discontinuous models in addition to supplementary functions for analysing model fits, in the context of SAR data. To this end, we provide a set of functions for fitting six piecewise regression models to SAR data, calculating confidence intervals around the breakpoint estimates (for certain models), comparing the models using various information criteria, and plotting the resultant model fits. Here, we present these functions and illustrate them using a selection of empirical datasets. These functions are implemented in the freely available and open-source R package ‘sars.’

Questions: Land use change, habitat fragmentation and biological invasion represent major drivers of global change that strongly interact to alter ecosystems. Following the breaking apart of forests into smaller fragments or the afforestation of former agricultural lands, biodiversity experiences drastic changes due to species loss and turnover over time. This leads to two important outcomes, namely extinction debt and invasion (colonization) credit, which both reflect the inertia of the system's response to environmental changes. Our study investigated the following questions: Is it possible to infer invasion credit from species–area relationship (SAR) residuals both for native and alien plants?Is there any trend linked with the degree of habitat fragmentation through time? Location: Somme, Oise and Aisne departments, northern France. Methods: We analyzed the pattern of SARs' residuals for native and alien vascular plant species separately across nine sets of forest fragments that differ by the landscape matrix they are embedded in (i.e., open field, bocage, forest), while considering plant richness, area and age of the 355 forest patches. Results: The relationship between alien and native SARs' residuals is positive across all landscapes, suggesting a lack of invasion credit. Instead, these results support the "rich get richer" hypothesis, that is a high environmental heterogeneity allows colonization by new species, be they native or alien. Interestingly, the relationship between alien and native residuals depends upon fragment age (i.e., time since patch creation) in the most intensively managed landscapes (i.e., open fields). In the latter, recent forest patches are more prone to alien invasion, as a likely consequence of increased alien propagule pressure (i.e., more sources and vectors for alien plants), increased forest invasibility (i.e., disturbance‐induced environmental heterogeneity), and decreased matrix permeability (i.e., natives are more dispersal‐limited than aliens). Conclusions: Our study provides new insights into alien species ecology, by showing that (i) it is not possible to infer "invasion credit" from the SAR's residuals; (ii) the invasion rate by alien species in forest fragments increases with their native species richness, and (iii) this relationship depends upon patch age in intensively managed landscapes. [ABSTRACT FROM AUTHOR]

Aim: The small‐island effect (SIE) and nestedness are two important patterns in the fields of island biogeography and community ecology. However, to date, no study has tried to integrate the SIE and nestedness pattern. Therefore, the aim of this study was to integrate these two biogeographical patterns by proposing a new integrative hypothesis. The integrative hypothesis posits that the degree of nestedness of the large island matrix will be larger than that of the small island matrix split by the threshold of the SIE. Location: Global. Taxon: Plants, invertebrates and vertebrates. Methods: We compiled 219 global datasets with both the presence‐absence matrices and the variables of area and species richness. We also collected six island characteristics influencing the SIE and nestedness patterns, that is island type, taxonomic group, area range, the number of islands, species range and matrix fill. We applied breakpoint regressions to detect SIEs and used the metric NODF (Nestedness metric based on Overlap and Decreasing Fill) to quantify nestedness. We then employed logistic regressions and an information‐theoretic approach to determine which combination of island characteristics was important in determining whether the integrative hypothesis was supported. Results: Among the 92 datasets in which SIEs were unambiguously detected, nestedness analyses showed that in 64 cases (69.6%) the values of NODFc (nestedness among sites) for the large island matrices were larger than those of the small island matrices. Matrix fill and area range were substantially important in determining whether the integrative hypothesis was supported. By contrast, island type, taxonomic group, the number of islands and species range received considerably less support. Main Conclusions: Our study was the first to integrate the SIE and nestedness pattern. Overall, we found prevalent support for our integrative hypothesis. The integration of the SIE and nestedness provides new and interesting insights into these two biogeographical patterns. [ABSTRACT FROM AUTHOR]

Islands are ideal research models to study ecological processes, as they vary in size, ecological conditions, and have clearly defined boundaries. Despite great advances in island research, comprehensive understanding of numerous aspects in island ecology is still lacking. Open questions include the effects of spatial scale on island biodiversity, community assembly processes, and the diversity of species forms and functions on islands. Here, I review recent studies investigating species assembly processes and resulting diversity patterns on small islands at local and global scales. I discuss how small-island communities are shaped by environmental, population-level, and species-level processes that differ in strength with island area. Functional trait-based approaches better explained these patterns than measures of species richness on small islands. Detailed ecological understanding of community assembly processes on islands is of paramount importance to conserve biodiversity in an increasingly fragmented natural world.

Research on island species–area relationships (ISAR) has expanded to incorporate functional (IFDAR) and phylogenetic (IPDAR) diversity. However, relative to the ISAR, we know little about IFDARs and IPDARs, and lack synthetic global analyses of variation in form of these three categories of island diversity–area relationship (IDAR). Here, we undertake the first comparative evaluation of IDARs at the global scale using 51 avian archipelagic data sets representing true and habitat islands. Using null models, we explore how richness‐corrected functional and phylogenetic diversity scale with island area. We also provide the largest global assessment of the impacts of species introductions and extinctions on the IDAR. Results show that increasing richness with area is the primary driver of the (non‐richness corrected) IPDAR and IFDAR for many data sets. However, for several archipelagos, richness‐corrected functional and phylogenetic diversity changes linearly with island area, suggesting that the dominant community assembly processes shift along the island area gradient. We also find that archipelagos with the steepest ISARs exhibit the biggest differences in slope between IDARs, indicating increased functional and phylogenetic redundancy on larger islands in these archipelagos. In several cases introduced species seem to have 're‐calibrated' the IDARs such that they resemble the historic period prior to recent extinctions. [ABSTRACT FROM AUTHOR]

Aim: Land use is a main driver of biodiversity loss worldwide. However, quantifying its effects on global plant diversity remains a challenge due to the limited availability of data on the distributions of vascular plant species and their responses to land use. Here, we estimated the global extinction threat of land use to vascular plant species based on a novel integration of an ecoregion‐level species‐area model and the relative endemism richness of the ecoregions. Location: Global. Methods: First, we assessed ecoregion‐level extinction threats using a countryside species–area relationship model based on responses of local plant richness to land use types and intensities and a high‐resolution global land use map. Next, we estimated global species extinction threat by multiplying the relative endemism richness of each ecoregion with the ecoregion‐level extinction threats. Results: Our results indicate that 11% of vascular plant species are threatened with global extinction. We found the largest extinction threats in the Neotropic and Palearctic realms, mainly due to cropland of minimal and high intensity, respectively. Main Conclusions: Our novel integration of the countryside species–area relationship and the relative endemism richness allows for the identification of hotspots of global extinction threat, as well as the contribution of specific land use types and intensities to this threat. Our findings inform where the development of measures to protect or restore plant diversity globally are most needed. [ABSTRACT FROM AUTHOR]

Aim: The small‐island effect (SIE), as an exception to the species–area relationship, has received much attention in true island systems. However, the prevalence and related patterns of the SIE have not been well evaluated in habitat island systems. Here, we aimed to identify the existence of SIE for habitat islands in fragmented landscapes and determine the key factors influencing species richness on small habitat islands. Location: Inner Mongolia Autonomous Region, China. Taxon: Vascular plants. Methods: Based on 78 grassland fragments in fragmented landscapes of the agro‐pastoral ecotone of northern China, we used piecewise regression, path analysis and null models to investigate the SIE of the species–area relationship. We then used a multi‐model selection to evaluate the impacts of four influencing factors (instability, isolation, habitat heterogeneity and surrounding productivity) on species richness (including habitat specialists and generalists) on small habitat islands within the range of SIE. Results: We found an obvious threshold of 5.1 ha in the species–area relationship, below which habitat island area had no direct and indirect effects on species richness. Small habitat islands (<5.1 ha) host a lower percentage of habitat specialists and a higher percentage of generalists. On small habitat islands, species richness was positively affected by habitat heterogeneity while negatively affected by instability and isolation. Habitat heterogeneity had the strongest effect on species richness, positively affecting specialist richness while negatively affecting generalist richness. Main Conclusions: There is an SIE in fragmented landscapes of the agro‐pastoral ecotone of northern China, which should be considered in biodiversity conservation. Habitat heterogeneity had a key role in determining the pattern of species richness, especially for small islands. Habitat specialists and generalists had different SIE‐related patterns. Our study highlights the importance of considering different ecological groups of species to improve our understanding of the SIE in fragmented habitats. [ABSTRACT FROM AUTHOR]

Aim: (i) To determine whether area and connectivity of temporary ponds can predict plant species diversity, and the diversity and abundance of different plant life histories; (ii) To explore whether pond connectivity with the river prior to river regulation predicts better plant diversity patterns than current pond connectivity, suggestive of possible effects of connectivity loss. Location: Eastern Carpathian Mountains, Romania, Europe. Methods: We fitted linear and generalized linear models (LM and GLM) to examine whether pond area and current distance from the Olt River predict plant species richness, Shannon diversity and relative cover of different social behaviour types and overall plant species richness and Shannon diversity. Using historical maps, we measured pond distance from the river ca. 60 years before the Olt River was regulated, and we refitted the LM and GLM models using pond area and past distance from the river as independent variables. Results: Total plant species richness increased with pond area, and it decreased with the distance from the river, but total plant Shannon diversity index was affected, positively, only by pond area. The strength of responses to pond area and connectivity of species richness, Shannon diversity and relative cover varied across the different social behaviour types. Past and current distances between ponds and riverbeds had similar effects on plant diversity, with some evidence for stronger effect of the present connectivity on specialist species Shannon diversity and a weaker effect on disturbance tolerants, generalists and competitors. Main Conclusions: Pond area and connectivity with the landscape are important predictors of the diversity of plant life history strategies, and therefore, useful tools in pond conservation. Consistent species richness and Shannon diversity responses of wetland specialists to pond area and connectivity make this life history type well suited for monitoring pond condition. [ABSTRACT FROM AUTHOR]

Plant invasions are generally associated with lower biodiversity and ecosystem function, but the impacts of plant invasions on species richness are often scale-dependent. Like species richness, metrics of community structure and quality likely differ in their sensitivity to plant invasions with area. Therefore, depending on the spatial scale of sampling, some metrics are unlikely to capture the impacts of plant invasions. Lonicera maackii is a shrub native to Asia and invasive across the eastern United States. The impact of L. maackii invasion on species richness and two floristic quality assessment (FQA) metrics, floristic quality index (FQI) and mean coefficient of conservatism (mean C), was studied across multiple spatial extents to determine the spatial breadth of the sensitivity of these metrics to plant invasions. We selected 12 forest plots: 6 uninvaded plots (<1% L. maackii cover) and 6 invaded plots (>70% L. maackii cover), which we divided into subplots of 1 m2, 62.5 m2, 125 m2, 250 m2, and 500 m2. Within each plot, we calculated average plant richness, mean C, and FQI for each spatial extent. Invaded plots displayed lower total richness at smaller spatial scales, with richness within L. maackii–invaded plots recovering to levels found among uninvaded plots at an extent of 62.5 m2. Invasion lowered both mean C and FQI at spatial extents ≤125 m2. Consequently, invasion impacts on FQA metrics likely manifest themselves at small spatial extents, and comparing invasion impact among management units should be carried out at these scales for proper comparison. [ABSTRACT FROM AUTHOR]

Microbial communities play a major role in disease, biogeochemical cycling, agriculture, and bioremediation. However, identifying the ecological processes that govern microbial community assembly and disentangling the relative impacts of those processes has proven challenging. Here, we propose that this discord is due to microbial systems being studied at different spatial, temporal, and phylogenetic scales. We argue that different processes dominate at different scales, and that through a more explicit consideration of spatial, temporal, and phylogenetic grains and extents (the two components of scale) a more accurate, clear, and useful understanding of microbial community assembly can be developed. We demonstrate the value of applying ecological concepts of scale to microbiology, specifically examining their application to nestedness, legacy effects, and taxa-area relationships of microbial systems. These proposed considerations of scale will help resolve long-standing debates in microbial ecology regarding the processes determining the assembly of microbial communities, and provide organizing principles around which hypotheses and theories can be developed.

The relationship between an island’s size and the number of species on that island—the island species–area relationship (ISAR)—is one of the most well-known patterns in biogeography and forms the basis for understanding biodiversity loss in response to habitat loss and fragmentation. Nevertheless, there is contention about exactly how to estimate the ISAR and the influence of the three primary ecological mechanisms that drive it — random sampling, disproportionate effects, and heterogeneity. Key to this contention is that estimates of the ISAR are often confounded by sampling and estimates of measures (i.e., island-level species richness) that are not diagnostic of potential mechanisms. Here, we advocate a sampling-explicit approach for disentangling the possible ecological mechanisms underlying the ISAR using parameters derived from individual-based rarefaction curves estimated across spatial scales. If the parameters derived from rarefaction curves at each spatial scale show no relationship with island area, we cannot reject the hypothesis that ISARs result only from random sampling. However, if the derived metrics change with island area, we can reject random sampling as the only operating mechanism and infer that effects beyond sampling (i.e., disproportionate effects and/or heterogeneity) are also operating. Finally, if parameters indicative of within-island spatial variation in species composition (i.e., β-diversity) increase with island area, we can conclude that intra-island compositional heterogeneity plays a role in driving the ISAR. We illustrate this approach using representative case studies, including oceanic islands, natural island-like patches, and habitat fragments from formerly continuous habitat, illustrating several combinations of underlying mechanisms. This approach will offer insight into the role of sampling and other processes that underpin the ISAR, providing a more complete understanding of how, and some indication of why, patterns of biodiversity respond to gradients in island area.

ABSTRACT The composition and diversity of avian microbiota are shaped by many factors, including host ecologies and environmental variables. In this study, we examine microbial diversity across 214 bird species sampled in Malawi at five major body sites: blood, buccal cavity, gizzard, intestinal tract, and cloaca. Microbial community dissimilarity differed significantly across body sites. Ecological theory predicts that as area increases, so does diversity. We tested the hypothesis that avian microbiota diversity is correlated with body size, used as a proxy for area, using comparative phylogenetic methods. Using Pagel’s lambda, we found that few microbial diversity metrics had significant phylogenetic signals. Phylogenetic generalized least squares identified a significant but weak negative correlation between host size and microbial diversity of the blood and a similarly significant but weakly positive correlation between the cloacal microbiota and host size among birds within the order Passeriformes. Phylosymbiosis, or a congruent branching pattern between host phylogeny and their associated microbiota similarity, was tested and found to be weak or not significant in four of the body sites with sufficient sample size (blood, buccal, cloaca, and intestines). Taken together, these results suggest that the avian microbiome is highly variable, with microbiota diversity demonstrating few clear associations with bird size. Finally, the blood microbiota have a unique relationship with host size. IMPORTANCE All animals coexist and interact with microorganisms, including bacteria, archaea, microscopic eukaryotes, and viruses. These microorganisms can have an enormous influence on the biology and health of macro-organisms. However, the general rules that govern these host-associated microbial communities are poorly described, especially in wild animals. In this paper, we investigate the microbial communities of over 200 species of birds from Malawi and characterize five body site bacterial microbiota in depth. Because the evolutionary relationships of the host underlie the relationship between any host-associated microbiota relationships, we use phylogenetic comparative methods to account for this relationship. We find that the size of a host (the bird) and the diversity and composition of the microbiota are largely uncorrelated. We also find that the general pattern of similarity between host phylogeny and microbiota similarity is weak. Together, we see that bird microbiota are not strongly tied to host size or evolutionary history.

A challenge: Variation is ubiquitous in nature across all spatial and temporal scales and underlies prominent ecological and evolutionary theories. Although understanding the causes and consequences of trait variation is a central goal of trait‐based ecology, the scaling of trait variance across space and time (variance scaling) is unresolved. A solution We argue that characterizing trait variance across spatio‐temporal scales using a combination of prominent power laws can elucidate the role of environmental variability in trait variation and potential mechanisms driving trait patterns. In particular, the species–time–area relationship and Taylor's power law help to establish a generalizable framework for developing and testing variance scaling theory. Finally, we outline priority research questions and tractable systems for answering them. Successional forests, long‐term forest monitoring networks and censuses of short‐lived taxa are ideal for coupling high‐resolution environmental data with measurements of trait variance across scales to test the models proposed here. Main conclusions: Characterizing the behaviour of variance across spatio‐temporal scales is feasible and a prerequisite for developing a predictive theory of trait‐based ecology. [ABSTRACT FROM AUTHOR]

In the northern Adriatic Sea, rocky outcrops called "trezze" or "tegnúe" are known as biodiversity hotspots. A total of 45 rocky outcrops were studied by using non-destructive photographic sampling during SCUBA diving. Ten invertebrate phyla with 196 taxa were recorded, 86% of which were determined at species level. Among them, 65% of the taxa were sessile, primarily represented by the phyla Porifera and Chordata. The aims of the study were: to characterize the species richness and composition of epifaunal invertebrates living on rocky outcrops; to test the efficiency of using the outcrop area as a predictor of epifauna richness, using the Arrhenius Species-Area Relationship (SAR) model; and to compare the expected richness resulting from the SAR model with the richness observed from the analysis of random photo-squares. Our results show that the SAR model describes the relationship between epibenthic species richness and outcrop size well and may have important practical applications for biodiversity estimations and nature conservation implications. It provides a useful tool, also in terms of economy and speed, to estimate the species richness of the benthic epifauna of the numerous outcrops that remain unsurveyed, based on their size. [ABSTRACT FROM AUTHOR]

Elevational gradients in species richness and species-area relationships are among the most interesting patterns in ecology and biogeography. Both patterns can be characteristic of the same system; however, current knowledge of how these patterns co-exist and how we can disentangle their contributions to biodiversity structure is insufficient. In this article, we tested the effect of elevation and area on the formation of plant species diversity patterns in the forest-free Javakheti Highlands (Georgia). Samples (170 plots) were collected within elevations of 1400-3100 m, and the diversity distribution was examined in relation to altitude, available band area, and sampling. In total, 564 species from 67 families were recorded. Plant species richness was highest at mid-elevations (1900-2200 m), irrespective of area and sampling effort. This was in line with other studies from the Caucasus indicating the generality of plant elevational diversity patterns in the region. Area was not an important predictor of species richness; however, this may be considered a result of insufficient sampling. Our study shows that more research is needed to understand the effect of area on patterns of elevational biodiversity distribution. [ABSTRACT FROM AUTHOR]

Any newly created area includes human-created habitats such as the mineral material of post-coal mining spoil heaps undergoing natural colonization and ecosystem development during the succession processes of vegetation colonization. The study of the factors that influence the succession dynamics, and the mechanisms behind this, have a long history (including the species-area relationship or Arrhenius equation). Nevertheless, the list of scientific questions is increasing. One of the significant issues in the study of these processes is the relationship between factors influencing the Biodiversity-Ecosystem Functioning (BEF) relationships. The main prerequisite is the relationships between the plant species' assemblage mechanisms including diversity and the variety of assembly rules concerning the environmental abiotic habitat processes and these properties are not straightforward. At the large scale, parameters such as age and area of the colonized sites are considered to be important. These relationships are more complicated in newly established post-mineral excavation habitats where novel ecosystems are developing. Regardless of the degree of disturbances, vegetation re-establishes in such environments, as a result of spontaneous succession, by the colonization and establishment of the best-adapted organisms. In the habitats of post-coal mining spoil heaps with pure oligotrophic mineral conditions, the non-analogous, newly formed composition of flora, fauna, and saprophytes has been stated in many previous field studies. This study aimed to explore the biodiversity versus area size relationships, in particular, it investigated the species composition and diversity found in the development of the spontaneous vegetation formed during primary succession on mineral substrate habitats of postcoal mining spoil heaps of different area sizes. We tested the hypothesis: species diversity of the vegetation patches on coal mine spoil heaps becomes more diverse on larger sites over time. These results indicate that the area size of the spoil heap significantly affects the diversity of the vegetation. Regardless of which of the characteristics of the vegetation type (dominant species) is compared, the vegetation on the heaps differs depending on its area size. [ABSTRACT FROM AUTHOR]

Species richness is a fundamental property of biodiversity patterns and is properly expressed by the species–area relationship (SAR), namely the increase in the number of species with the area. Here, we studied and explored the species–area relationship with respect to vascular plant species in Italy and compared vascular plant richness among Italian administrative regions. Concerning the entire vascular flora (native and alien), the best-performing formula is the Arrhenius’ Power function: S = c Az. The constants of this function are c = 241.2 and z = 0.281. The best-performing formula concerning just native (c = 245.2 and z = 0.263) and alien (c = 10.1 and z = 0.404) richness is the Power function as well. The floristically richest Italian regions considering the entire flora are Liguria, Friuli Venezia Giulia, and Trentino-Alto Adige, which are also the regions that are richest in alien flora unfortunately. Regions of particular naturalistic interest are Abruzzo, Valle d’Aosta, and Molise, because only these three regions exhibit native floristic richness that is higher than expected, and this is coupled with an alien floristic richness that is lower than expected. On the contrary, four regions (Lombardia, Veneto, Toscana, and Emilia-Romagna) show potentially severe conservation problems due to biological invasions since they experience native floristic richness that is lower than expected, with an alien floristic richness that is higher than expected. This study offers for the first time the ‘c’ and ‘z’ constants specifically calibrated at the national level for Italian vascular flora. The availability of such constants allows the calculation of the number of expected species for a given area to be investigated, providing a robust starting hypothesis for floristic studies.

Aim: The species–area relationship (SAR) is one of the most distinctive biogeographic patterns, but global comparisons of the SARs between island and mainland are lacking for microbial taxa. Here, we explore whether the form of the SAR and the drivers of species richness, including area, environmental heterogeneity, climate and physico‐chemistry, differ between islands and similarly sized areas on mainland, referred to as continental area equivalents (CAEs). Location: Global. Taxon: Stream benthic diatoms. Methods: We generated CAEs on six continental datasets and examined the SARs of CAEs and islands (ISAR). Then, we compared CAEs and islands in terms of total richness and richness of different ecological guilds. We tested the factors contributing to richness in islands and CAEs with regressions. We used structural equation models to determine the effects of area versus environmental heterogeneity, climate and local conditions on species richness. Results: We found a non‐significant ISAR, but a significant positive SAR in CAEs. Richness in islands was related to productivity. Richness in CAEs was mainly dependent on area and climate, but not directly on environmental heterogeneity. Species richness within guilds exhibited inconsistent relationships with island isolation and area. Main conclusions: Ecological and evolutionary processes shaping diatom island biogeography do not depend on area at the worldwide scale probably due to the presence of distinct species pool across islands. Conversely, area was an important driver of diatom richness in continents, and this effect could be attributed to dispersal. Continents had greater richness than islands, but this was a consequence of differences in environmental conditions such as specific island climatic conditions. We stress the need for more island data on benthic diatoms, particularly from archipelagos, to better understand the biogeography of this most speciose group of algae. [ABSTRACT FROM AUTHOR]

It has been a century since the species-area relationship (SAR) was first proposed as a power law to explain how species richness scales with area. There have been many attempts to explain the origin of this predominant form. Apart from the power law, numerous empirical studies also report a semi-log form of the SAR, but very few have addressed its incidence. In this work, we test whether these relationships could emerge from the assembly of large random communities on island-like systems. The clustering of same-species individuals is central to our results, which we incorporate by modifying the self-interaction term in the generalized Lotka-Volterra equations. Our analysis demonstrates that the two most widely reported relationship forms can emerge due to differences in immigration rates and skewness towards weak interactions. We particularly highlight the incidence of the semi-log SAR for low immigration rates from a source pool, which is consistent with several previous empirical studies. The two SAR forms might show good fits to data over a large span of areas but a power-law overestimates species richness on smaller islands in remote archipelagoes. [ABSTRACT FROM AUTHOR]

The explanations behind observations of global patterning in species diversity pre‐date the field of ecology itself. The generation of new species–area theories, in particular, far outpaces their falsification, resulting in a centuries‐old accumulation in species diversity theories. We use historical assessment and new data analysis to argue that one of the earliest recognized and most consistent patterns in species diversity is not strictly an ecological phenomenon and, when ecological mechanism is invoked, the range of potential mechanisms is too numerous for tractable hypothesis falsification. We provide a historical parallel in that the normal distribution once was treated as a pattern assuming a biological mechanism rather than a statistical distribution that can be generated by biological and non‐biological forces. Similarly, power law distributions are ubiquitous in aggregated data, such as the species–area relationship. That nearly identical broad‐scale aggregation patterns are observed for both ecological and non‐ecological data as a function of area suggest that these broad‐scale patterns reflect a statistical distribution that, in itself, cannot be used to discern between or among ecological and non‐ecological mechanisms. We argue that by seeking processes in such a ubiquitous pattern, ecologists may read ecological mechanism into statistical patterns, and we suggest that falsifying broad‐scale diversity distribution hypotheses should be a greater priority than generating or parameterizing new ones. [ABSTRACT FROM AUTHOR]

Although groups of small habitat patches often support more species than large patches of equal total area, their biodiversity value remains controversial. An important line of evidence in this debate compares species accumulation curves, where patches are ordered from small–large and large–small (aka 'SLOSS analysis'). However, this method counts species equally and is unable to distinguish patch size dependence in species' occupancies. Moreover, because of the species–area relationship, richness differences typically only contribute to accumulation in small–large order, maximizing the probability of adding species in this direction. Using a null model to control for this, I tested 202 published datasets from archipelagos, habitat islands and fragments for patch size dependence in species accumulation and compared conclusions regarding relative species accumulation with SLOSS analysis. Relative to null model expectations, species accumulation was on average 2.7% higher in large–small than small–large order. The effect was strongest in archipelagos (5%), intermediate for fragments (1.5%) and smallest for habitat islands (1.1%). There was no difference in effect size among taxonomic groups, but each shared this same trend. Results suggest most meta-communities include species that either prefer, or depend upon, larger habitat patches. Relative to SLOSS analysis, null models found lower frequency of greater small-patch importance for species representation (e.g., for fragments: 69 vs 16% respectively) and increased frequency for large patches (fragments: 3 vs 25%). I suggest SLOSS analysis provides unreliable inference on species accumulation and the outcome largely depends on island species–area relationships, not the relative diversity value of small vs large patches. [ABSTRACT FROM AUTHOR]

One of the most investigated patterns in species diversity is the so-called latitudinal gradient, that is, a decrease in species richness from the equator to the poles. However, few studies investigated this pattern in insects at a global scale because of insufficient taxonomic and biogeographical information. Using estimates of earwig species richness at country level, their latitudinal diversity gradient was modelled globally and for the two hemispheres separately after correcting for differences in country areas. Separate analyses were also conducted for mainland and island countries. All analyses clearly indicated the existence of latitudinal gradients. The most plausible explanation for the observed pattern is the so-called tropical conservatism hypothesis, which postulates (1) a tropical origin of many extant clades, (2) a longer time for cladogenesis in tropical environments thanks to their environmental stability, and (3) a limited ability of historically tropical lineages to adapt to temperate climates. Earwigs probably evolved on Gondwana and secondarily colonized the Northern Hemisphere. This colonization was hampered by both geographical and climatic factors. The Himalayan orogenesis obstructed earwig dispersal into the Palearctic region. Additionally, earwig preferences for warm/hot and humid climates hampered the colonization of temperate regions. Pleistocene glaciation further contributed to reducing diversity at northern latitudes. [ABSTRACT FROM AUTHOR]

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The influence of island dynamics and characteristics on taxonomic diversity, particularly species richness, are well studied. Yet, our knowledge on the influence of island dynamics and characteristics on other facets of diversity, namely functional and phylogenetic diversity, is limited, constraining our understanding of assembly processes on islands (e.g. biogeographic history, dispersal and environmental filtering and species interactions). Using barrier islands, a highly dynamic and so far, understudied island type, we investigate how multiple facets of vascular plant diversity (functional, phylogenetic and taxonomic diversity) are shaped by island geomorphology, modern and historic area, and habitat heterogeneity. In line with our expectation, historical dynamics in island geomorphology affected phylogenetic and taxonomic diversity via habitat heterogeneity. However, island area was the best predictor across all facets of diversity. Specifically, larger islands had higher functional and phylogenetic diversity than expected by chance while most of the smaller islands had lower diversity. The influence of area on functional diversity acted via habitat heterogeneity, with habitat heterogeneity influencing negatively functional diversity. Our results suggest that larger islands accumulate functionally and phylogenetically unique species. Further, results for functional diversity pointed towards potential area–heterogeneity trade‐offs, with these trade‐offs likely resulting from increased interspecific competition favoring a specific set of trait values (of stronger competitors), particularly on smaller islands. Together, these results demonstrate that going beyond taxonomic diversity contributes to identifying underlying processes shaping diversity–area relationships. [ABSTRACT FROM AUTHOR]