Species-area Relationship Research Articles

Global decline in capacity of coral reefs to provide ecosystem services

Global decline in capacity of coral reefs to provide ecosystem services

Considering habitat conversion and fragmentation in characterisation factors for land-use impacts on vertebrate species richness

Human land use is one of the primary threats to terrestrial species richness and is considered a priority for meeting global sustainability and biodiversity targets. Decision-support tools, such as life cycle assessment (LCA), are widely used for developing strategies to achieve such objectives. Currently available life cycle impact assessment (LCIA) methods apply the countryside species-area relationship (c-SAR) to quantify habitat conversion impacts on species richness. However, additional effects of habitat fragmentation are yet ignored in these assessments. We use the species-habitat relationship (SHR), an adaptation of the c-SAR that considers both habitat conversion and fragmentation effects, to develop a new set of land-use characterisation factors for 702 terrestrial ecoregions (in 238 countries), four land-use types (urban, cropland, pasture, and forestry), and four taxonomic groups (amphibians, birds, mammals, and reptiles; plus the aggregate of these vertebrate groups). The SHR generally predicts higher per-area impacts of land-use than the impacts estimated by the c-SAR (a median relative difference of +9%), indicating that land-use impacts may be systematically underestimated when ignoring fragmentation effects. Whereas per-area impacts of land-use on regional species richness are highest in temperate regions, reflecting the diminished extent of natural habitat, per-area impacts of land-use on global species richness are highest in the subtropics, reflecting the importance of tropical regions and islands to global vertebrate species diversity. The large variety in magnitude of land-use impacts across the world's regions emphasizes the importance of regionalised assessments. The set of characterisation factors proposed here can be readily used in environmental decision-making.

How sampling scheme and species-area scale contribute to select the best statistical functions for upscaling plant species richness

Species–area curve is widely used to describe biological diversity across spatial scales. However, there are major ecological and statistical limitations in its application and inference, such as sampling methods, species-area scales, and statistical functions that must be considered in diversity assessment. This study aimed to explain relations among sampling methods, species-area curve scales and statistical functions in the Perk forested catchment, Zagros forests, western Iran. We studied plant diversity during the peak of the growing season, from early April to late May, 2019. The stratified random sampling was applied to collect species richness data on the same sized plots (4m2). The mean of data from noncontiguous plots was used to construct Scheiner's type IIIB curve. A comprehensive set of species-area models including five convex and three sigmoid models were tested. Akaike information criterion (AIC) and Bayesian information criterion (BIC) were used to choose the best-fitted function model. Furthermore, the Log Error of Extrapolation (LEE) was used to assess the reliability of extrapolation. Both AIC and BIC results suggested that the Lomolino and Cumulative Weibull functions as the best-fit curves for extrapolating species richness beyond sampling area. However, the LEE showed the superiority of the Rational function. This discrepancy between LEE and both AIC and BIC introduced models originates from the LEE limitation of application to tenfold of the sampling area. This study showed that the sampling scheme and the study scale are the two important factors in the shape of statistical function (convex or sigmoid) which is using in constructing species-area curves. In contrast to the prevailing use of power function, the results showed that in a broader scale like the landscape scale, the Lomolino and Cumulative Weibull functions are superior in estimating species richness in Zagros forests, western Iran.

Meadow degradation increases spatial turnover rates of the fungal community through both niche selection and dispersal limitation

The alpine meadow ecosystem, as the main ecosystem of the Qinghai-Tibet Plateau, has been heavily degraded over the past several decades due to overgrazing and climate change. Although soil microorganisms play key roles in the stability and succession of grassland ecosystems, their response to grassland degradation has not been investigated at spatial scale. Here, we systematically analyzed the spatial turnover rates of soil prokaryotic and fungal communities in degraded and undegraded meadows through distance-decay relationship (DDR) and species area relationship (SAR), as well as the community assembly mechanisms behind them. Although the composition and structure of both fungal and prokaryotic communities showed significant changes between undegraded and degraded meadows, steeper spatial turnover rates were only observed in fungi (Degraded Alpine Meadow β = 0.0142, Undegraded Alpine Meadow β = 0.0077, P < 0.05). Mantel tests indicated that edaphic variables and vegetation factors showed significant correlations to the β diversity of fungal community only in degraded meadow, suggesting soil and vegetation heterogeneity both contributed to the variation of fungal community in that system. Correspondingly, a novel phylogenetic null model analysis demonstrated that environmental selection was enhanced in the fungal community assembly process during meadow degradation. Interestingly, dispersal limitation was also enhanced for the fungal community in the degraded meadow, and its relative contribution to other assembly process (i.e. selection and drift) showed a significant linear increase with spatial distance, suggesting that dispersal limitation played a greater role as distance increased. Our findings indicated the spatial scaling of the fungal community is altered during meadow degradation by both niche selection and dispersal limitation. This study provides a new perspective for the assessment of soil microbial responses to vegetation changes in alpine areas.

Species-Area Relationships in Urban Ponds Differ between Wild and Human-Fed Domesticated Birds

We sampled 70 urban ponds (0.001 to >1 ha) in Rome, Italy, to obtain richness and abundance data for wintering wild birds and domestic birds in relation to pond size. The aim was to test the hypothesis that the species-area relationship differs between wild and domestic birds, with the presence of the latter linked with anthropogenic factors, not pond area. We detected eight domesticated avian taxa and 19 wild species at 26 sites. Whereas there was a significant relationship between the number of wild bird species and pond area, the diversity of domestic taxa appeared not to be correlated with area (power function; Levenberg-Marquardt approach). Species-area relationships showed a lower variance in domestic taxa when compared with wild species. As smaller ponds in urban landscapes can host a higher number of domestic taxa than wild species, there may be implications both for increasing risk of disease transmission and for biodiversity perception among urban citizens.

Synthesis reveals that island species–area relationships emerge from processes beyond passive sampling

AbstractAimThe island species–area relationship (ISAR) quantifies how the number of species increases as the area of an island or island‐like habitat gets larger and is one of the most general patterns in ecology. However, studies that measure the ISAR often confound variation in sampling methodology and analyses, precluding appropriate syntheses of its underlying mechanisms. Most ISAR studies use only presence–absence data at the whole‐island scale, whereas we planned to use a framework that applies individual‐based rarefaction to synthesize whether and how the ISAR differs from the null expectation of the passive sampling hypothesis.LocationFive hundred and five islands from 34 different archipelagos across the world, including oceanic islands, lake islands and forest islands.Major taxa studiedLocal assemblages of plants, invertebrates, herpetofauna, birds and mammals.MethodsWe collated local‐scale species abundance data from multiple archipelagos (median of 12 islands per study) and used a rarefaction‐based approach to synthesize the relationship between island size and (1) sample effort‐controlled rarefied species richness, or (2) an effective number of species derived from the probability of interspecific encounter (an index of community evenness).ResultsWhen we applied rarefaction to control for sampling effort, the numbers of species and their relative abundances across all studies differed from the passive sampling hypothesis. Our measure of evenness also increased with island size, suggesting that the disproportionate effects we observed influenced both rarer and more common species. We found few associations between the slope of this effect and island type or taxon, but we did find that island archipelagos with greater elevational heterogeneity also deviated more from the null expectation than those with less heterogeneity.Main conclusionsUsing a synthetic approach across island archipelagos, we reject the null expectation that passive sampling causes the ISAR and instead suggest that ecological mechanisms leading to disproportionate (non‐random) effects on larger relative to smaller islands are predominant.

Island biogeography: an avenue for research in bryology

In the present review, we provide an updated account on the level of knowledge in island bryophyte biogeography. In the framework of the 50 most fundamental questions for present and future island biology research highlighted by Patiño et al. (2017), we summarize current knowledge in bryophyte island biogeography and outline main research avenues for the future in the field. We found that only about 50% of the key current questions in island biogeography have been addressed to some extent, at least once, in bryophytes. Even fundamental questions that have caught the attention of ecologists since more than one century, such as the species-area relationship, have only rarely been dealt with in bryophytes. The application of the Island Biogeography Theory therefore opens an avenue for research in bryology, and we discuss the most salient features, including species and community phylogenetics, biotic interactions, and invasion biology.

Neighbourhood-based evidence of tree diversity promotion by beech in an old-growth deciduousconiferous mixed forest (Eastern Carpathians)

Neighbourhood models are useful tools for understanding the role of positive and negative interactions in maintaining the tree species diversity in mixed forests. Under such a presumption, we aimed at testing several hypotheses concerning the mechanisms of autogenic species coexistence in an old-growth, beech-fir-spruce stand, which is part of the Slătioara forest reserve (Eastern Carpathians). Univariate/bivariate spatial point pattern analyses, the individual tree species-area relationship, the species mingling analysis and generalised linear mixed models of neighbour interference were applied on data concerning the position and allometry of all saplings and trees occurring within a 0.24 ha plot. The monospecific distribution of either beech or spruce saplings did not support the spatial segregation hypothesis. There was no evidence of conspecific negative distance dependence, as no spatial segregation was detected between the saplings and trees of any species. Within 4 m-neighbourhood, the beech saplings appeared as diversity accumulators, which might be indicative of indirect facilitation (e.g., herd protection hypothesis). At tree stage, none of the three species showed either accumulator or repeller patterns in their neighbourhood with respect to sapling species richness. Signals of positive and negative interspecific association were found in tree-sized beech (at scales of 10 to 20 m) and spruce (at scales of 4 to 17 m), respectively. The former, highly interspersed pattern is in accordance with the hypothesis of positive complementary effects, whereas the latter, poorly intermingled pattern is probably linked to the unexpected, positive neighbouring effect of spruce trees on the stem growth of their conspecific saplings. Such self-favouring process might be due to a facilitative below-ground mechanism. Conversely, the beech saplings were suppressed through interference from the neighbouring conspecific trees. The beech appears to be the key promoter of tree species coexistence in the study forest stand, in contrast to the low interspersion of spruce in the overstorey leading to lower local tree diversity.

Neighbourhood-based evidence of tree diversity promotion by beech in an old-growth deciduous-coniferous mixed forest (Eastern Carpathians)

Neighbourhood models are useful tools for understanding the role of positive and negative interactions in maintaining the tree species diversity in mixed forests. Under such a presumption, we aimed at testing several hypotheses concerning the mechanisms of autogenic species coexistence in an old-growth, beech-fir-spruce stand, which is part of the Slatioara forest reserve (eastern Carpathians). Univariate/bivariate spatial point pattern analyses, the individual tree species-area relationship, the species mingling analysis and generalised linear mixed models of neighbour interference were applied on data concerning the position and allometry of all saplings and trees occurring within a 0.24 ha plot. The monospecific distribution of either beech or spruce saplings did not support the spatial segregation hypothesis. There was no evidence of conspecific negative distance dependence, as no spatial segregation was detected between the saplings and trees of any species. Within 4 m-neighbourhood, the beech saplings appeared as diversity accumulators, which might be indicative of indirect facilitation (e.g., herd protection hypothesis). At tree stage, none of the three species showed either accumulator or repeller patterns in their neighbourhood with respect to sapling species richness. Signals of positive and negative interspecific association were found in tree-sized beech (at scales of 10 to 20 m) and spruce (at scales of 4 to 17 m), respectively. The former, highly interspersed pattern is in accordance with the hypothesis of positive complementary effects, whereas the latter, poorly intermingled pattern is probably linked to the unexpected, positive neighbouring effect of spruce trees on the stem growth of their conspecific saplings. Such self-favouring process might be due to a facilitative below-ground mechanism. Conversely, the beech saplings were suppressed through interference from the neighbouring conspecific trees. The beech appears to be the key promoter of tree species coexistence in the study forest stand, in contrast to the low interspersion of spruce in the overstorey leading to lower local tree diversity.

Ecosystem state assessment after more than 100 years since planting for dune consolidation

The assessment of the ecosystem state is fundamental to understand the success of ecological rehabilitation, especially in the long term. We aim to evaluate the rehabilitation success of a unique Mediterranean dune system site along the Tyrrhenian coast of Italy which underwent a dune consolidation intervention and species planting at the beginning of the twentieth century after the destruction of the natural ecosystem. We used three nearby non‐rehabilitated protected coastal sites with different degrees of disturbance as reference sites encompassing different potential rehabilitation outcomes of the target site. To assess the overall result of the intervention, we used several plant characteristics and measured taxonomic and functional beta‐diversity between all sites. We compared the proportions of typical and ruderal species of dune habitat types across sites. We further used the species–area relationship to examine if the number of observed species in our sites differed from the expected. Our analyses revealed that the rehabilitated site was taxonomically and functionally more similar to the least disturbed site. We suggest that plant characteristics arising from botanical inventories can be fruitfully used in rehabilitation assessment as they value the taxonomic and functional species diversity at the community scale. We conclude that plant characteristics compared across sites are useful tools in ecosystem state assessment if they reflect the ecological functions and conservation values of the natural ecosystems.

Nested versus Independent Sampling: Solving the Mystery of Contradictory Species-Area Relationships.

AbstractSpecies-area relationships (SARs) describe how the number of species increases with the size of the area surveyed. They usually take the form of a power law on regional spatial scales. A metareview of empirical data has shown that the exponent of the power law is larger on average when the areas are sampled in a nested manner, compared with sampling of isolated areas such as islands or nature reserves of different sizes. Because this finding contradicts ecological reasoning, we performed computer simulations of three qualitatively different models that generate species distributions in space and time driven by the mechanisms of speciation, dispersal, and extinction. We find that in all cases and over a wide parameter range the SARs obtained by nested sampling have a smaller slope on the regional scale than those obtained by independent sampling. However, the slopes change considerably with spatial scale and in a different manner for the two sampling methods. By evaluating the spatial scales on which the two types of empirical data were taken, we can explain the discrepancy between simulation results and empirical data.

Measuring ecological status and tree species diversity in Eastern Ghats, India

The present study assessed the ecological status and tree diversity of Visakhapatnam forest area, part of Eastern Ghats, India, using systematic and standard sampling techniques. Tree species composition, similarity, diversity, species richness, structure of trees and disturbance levels in deciduous forests based on census of all trees with diameter at breast height ≥ 15 cm were studied. A systematic sampling protocol was adopted and twelve belt transects (5 × 1000 m), a total of 6 ha plots were laid for the vegetation survey. In all the plots, a total of 2999 individuals (mean density 500 ha−1) covering 151 tree species pertaining to 106 genera and 46 families were measured. The data revealed that the forest has a moderate value for the tree species diversity index (H′) which is varied from 3.26 to 4.12. Species richness varied from 38 to 79 species ha−1 and stand density from 328 to 718 individuals ha−1 with an average basal area of 14.7 m2ha−1. Xylia xylocarpa, Lannea coromandelica, Anogeissus latifolia and Wrightia tinctoria were the predominant plant taxa in the study area. Highest species richness recorded from Euphorbiaceae with 12 species immediately followed by Moraceae, Rubiaceae and Verbenaceae (9 species each). The species-area curve did not reach an asymptote in all the plots. The present study can provide baseline information for the effective management and restoration of forest tree species with conservation significance emphasized in highly disturbed and human impacted forest stands.

The species–area relationship in ant ecology

AbstractAimThe positive relationship between species richness and area—the species–area relationship (SAR)—is a key principle in ecology. Previous studies show large variation in the SAR across taxa collectively indicating the necessity of a taxon‐focused approach to accurately evaluate biodiversity scaling patterns. Ants are ideal for this given their global distribution and role in ecosystem functioning. Using data from insular ant communities, this study quantified and investigated various attributes of ant SARs and reviewed the SAR literature for ant faunas, world‐wide, to identify specific areas for improvement.LocationIslands around the world.TaxonAnts (Hymenoptera: Formicidae).MethodsWe aggregated data on species richness and island characteristics from previous studies on ant SARs to evaluate effects of climate, biogeographic realm, and latitude on slope values from these studies. A multimodel inference approach was used to determine the form of the different SARs, and whether there were any differences between mainland and insular SARs. We also assessed differences between mainland and insular SAR slopes and intercepts. To seek a general slope coefficient for ants, we used a mixed‐effect model. Finally, we tested for potential thresholds in the global insular SAR using piecewise regression models.ResultsThere was a negative relationship between SAR slopes and precipitation in both mainland and insular SARs, while SAR slopes and intercept values were higher in mainland compared to insular systems. Strong evidence of thresholds emerged in the global insular SAR. Finally, a general slope of 0.16 was observed for insular systems, which is lower than found in previous studies.Main ConclusionsA taxon‐focused approach proves to showcase unexpected patterns in the SAR. Ant diversity increases faster across area in mainland areas compared to true islands. The influences of climate and biogeographic realms on the ant SAR warrant deeper study. Our review highlights knowledge gaps in the ant SAR that also extend to other taxa, such as the effects of nonnative species on the SAR.

Shifting macroecological patterns and static theory failure in a stressed alpine plant community

AbstractAccumulating evidence suggests that ecological communities undergoing change in response to either anthropogenic or natural disturbances exhibit macroecological patterns that differ from those observed in similar types of communities in relatively undisturbed sites. In contrast to such cross‐site comparisons, however, there are few empirical studies of shifts over time in the shapes of macroecological patterns. Here, we provide a dramatic example of a plant community in which the species–area relationship and the species‐abundance distribution change markedly over a period of six years. These patterns increasingly deviate from the predictions of the maximum entropy theory of ecology (METE), which successfully predicts macroecological patterns in relatively static systems. The error in the species–area relationship prediction additionally correlates over time with increased stress measured as mortality minus recruitment, providing a link between demography and the failure of macroecological theory. Information on the dynamic state of an ecosystem inferred from snapshot measurements of macroecological community structure can potentially assist in identifying causes and consequences of disturbance and extending the domain of current theories and models to disturbed ecosystems.

Common spatial patterns of trees in various tropical forests: Small trees are associated with increased diversity at small spatial scales.

Tropical forests are notable for their high species diversity, even on small spatial scales, and right‐skewed species and size abundance distributions. The role of individual species as drivers of the spatial organization of diversity in these forests has been explained by several hypotheses and processes, for example, stochastic dilution, negative density dependence, or gap dynamics. These processes leave a signature in spatial distribution of small trees, particularly in the vicinity of large trees, likely having stronger effects on their neighbors. We are exploring species diversity patterns within the framework of various diversity‐generating hypotheses using individual species–area relationships. We used the data from three tropical forest plots (Wanang—Papua New Guinea, Barro Colorado Island—Panama, and Sinharaja—Sri Lanka) and included also the saplings (DBH ≥ 1 cm). Resulting cross‐size patterns of species richness and evenness reflect the dynamics of saplings affected by the distribution of large trees. When all individuals with DBH ≥1 cm are included, ~50% of all tree species from the 25‐ or 50‐ha plot can be found within 35 m radius of an individual tree. For all trees, 72%–78% of species were identified as species richness accumulators, having more species present in their surroundings than expected by null models. This pattern was driven by small trees as the analysis of DBH >10 cm trees showed much lower proportion of accumulators, 14%–65% of species identified as richness repellers and had low richness of surrounding small trees. Only 11%–26% of species had lower species evenness than was expected by null models. High proportions of species richness accumulators were probably due to gap dynamics and support Janzen–Connell hypothesis driven by competition or top‐down control by pathogens and herbivores. Observed species diversity patterns show the importance of including small tree size classes in analyses of the spatial organization of diversity.

The role of protected and unprotected forest remnants for mammal conservation in a megadiverse Neotropical hotspot

The Brazilian Atlantic Forest of Southern Bahia is a megadiverse region given its remarkable number of species and endemism. Despite being a priority region for biodiversity conservation, the role of protected and unprotected forest remnants for long-term species conservation is unknown. Here, we unveil the main patterns of occurrence and distribution of medium- and large-sized mammals in remnants of the Atlantic Forest of Southern Bahia, to generate subsidies for applied conservation strategies. We recorded mammals using camera-traps, active search, and/or line-transect surveys and complemented our species list with literature data. We thus obtained information on richness attributes, relative abundance, and biomass of mammal species per forest remnant, compared assemblages in protected and unprotected areas, and finally investigated both species-area and biomass-area relationships. From 72 forest remnants assessed, we recorded 45 mammal species, including 19 threatened locally. Protected areas were richer in species, especially concerning threatened ones, and concentrated most of the mammal biomass, which presented consistently low values for most areas. The positive and significant species-area and biomass-area relationships further corroborate these patterns since protected areas are larger in size. Despite the historic anthropogenic pressures, we conclude that Southern Bahia still harbors an expressive mammal diversity, with protected areas being critical to maintain most of the species' richness and biomass across the entire region. Nevertheless, small unprotected remnants (<100 ha) safeguard mammal species, including threatened ones, stressing their importance to maintain mammal assemblages in one of the most important hotpoints of the entire biome.

Spatiotemporal patterns and ecological consequences of a fragmented landscape created by damming.

BackgroundDamming disrupts rivers and destroys neighboring terrestrial ecosystems through inundation, resulting in profound and long-lasting impacts on biodiversity and ecosystem processes far beyond the river system itself. Archipelagos formed by damming are often considered ideal systems for studying habitat fragmentation.MethodsHere we quantified the island attributes and landscape dynamics of the Thousand Island Lake (TIL) in China, which is one of the several long-term biodiversity/fragmentation research sites around the world. We also synthesized the major findings of relevant studies conducted in the region to further ecological understanding of damming and landscape fragmentation.ResultsOur results show that the vegetations on islands and the neighboring mainland were both recovering between 1985 and 2005 due to reforestation and natural succession, but the regeneration was partly interrupted after 2005 because of increasing human influences. While major changes in landscape composition occurred primarily in the lakefront areas and near-lakeshore islands, landscape patterns became structurally more complex and fragmented on both islands and mainland. About 80 studies from the TIL region show that the genetic, taxonomic, functional, and phylogenetic diversity on these islands were mainly influenced by island area at the patch scale, but fragmentation per se also affected species composition and related ecological processes at patch and landscape scales. In general, islands had lower species diversity but a steeper species-area relationship than the surrounding mainland. Fragmentation and edge effects substantially hindered ecological succession towards more densely vegetated forests on the islands. Environmental heterogeneity and filtering had a major impact on island biotic communities. We hypothesize that there are multiple mechanisms operating at different spatial scales that link landscape fragmentation and ecological dynamics in the TIL region, which beg for future studies. By focusing on an extensive spatiotemporal analysis of the island-mainland system and a synthesis of existing studies in the region, this study provides an important foundation and several promising directions for future studies.

Saprotrophic fungal diversity predicts ectomycorrhizal fungal diversity along the timberline in the framework of island biogeography theory

Island biogeography theory (IBT) is one of the most fruitful paradigms in macroecology, positing positive species-area and negative species-isolation relationships for the distribution of organisms. Biotic interactions are also crucial for diversity maintenance on islands. In the context of a timberline tree species (Betula ermanii) as “virtual island”, we surveyed ectomycorrhizal (EcM) fungal diversity along a 430-m vertical gradient on the top of Changbai Mountain, China, sampling fine roots and neighboring soils of B. ermanii. Besides elevation, soil properties and plant functional traits, endophytic and saprotrophic fungal diversity were assessed as candidate predictors to construct integrative models. EcM fungal diversity decreased with increasing elevation, and exhibited positive diversity to diameter at breast height and negative diversity to distance from forest edge relationships in both roots and soils. Integrative models further showed that saprotrophic fungal diversity was the strongest predictor of EcM fungal diversity, directly enhancing EcM fungal diversity in roots and soils. Our study supports IBT as a basic framework to explain EcM fungal diversity. The diversity-begets-diversity hypothesis within the fungal kingdom is more predictive for EcM fungal diversity within the IBT framework, which reveals a tight association between saprotrophic and EcM fungal lineages in the timberline ecosystem.

Distinguishing effects of area per se and isolation from the sample‐area effect for true islands and habitat fragments

The island species area relationship (ISAR) is an important tool for measuring variation in species diversity in variety of insular systems, from true‐island archipelagoes to fragmented terrestrial landscapes. However, it suffers from several limitations. For example, due to the sample‐area effect, positive relationships between species and area cannot be directly interpreted as evidence for deterministic effects of area per se. Additionally, richness‐based analyses may obscure species‐level responses to area and isolation that may better inform conservation practice. Here, we use random placement models to control for variation in abundance, occupancy and richness associated with the sample‐area effect, allowing deterministic effects of area and isolation, and how they vary with species' functional traits, to be resolved using linear mixed effects models. We demonstrate the utility of this approach using a butterfly assemblage persisting on a naturally fragmented landscape of lake islands. The ISAR did not significantly deviate from random placement in relation to island area, isolation or habitat diversity, supporting stochastic assembly consistent with the sample‐area effect. Such inferences support the habitat amount hypothesis, which prioritizes preserving the maximum amount of habitat irrespective of its degree of fragmentation. However, species‐level analyses demonstrated that species' abundances were significantly lower on both smaller and more isolated islands than what is predicted by the sample‐area effect. Moreover, effects of area per se were significantly greater for smaller, less mobile and rare species. Species' occurrences also significantly deviated from predictions of the sample‐area effect in relation to island isolation. Thus, our approach illustrates that richness‐based analyses not only result in incorrect inferences on mechanisms underlying ISARs, but also obscure important effects of area per se and isolation on individual species that vary with functional traits. We therefore suggest that these effects should not be solely inferred from richness‐based analyses, but rather evaluated on a species‐by‐species basis.

From Island Biogeography to Conservation: A Multi-Taxon and Multi-Taxonomic Rank Approach in the Tuscan Archipelago

Investigating the drivers that support species richness (S) in insular contexts can give insights for the conservation of insular biodiversity. Our aim was to decouple the effect of drivers (island area, distance from mainland and habitat diversity) accounted in three hypotheses or a combination of them in explaining S in seven islands of the Tuscan Archipelago: Area (species–area relationship, SAR), area and distance from mainland (equilibrium hypothesis, EQH) and habitat (habitat diversity hypothesis, HDH). We used published and original datasets to assess S (except aliens) for 42 taxa (14 animal and 28 plant taxa) in each island, and we used S as the dependent variable and the drivers as covariates in regression models. In 31 taxa, the data supported one of the tested hypotheses or a combination of them, and the most commonly supported hypotheses were SAR (12 taxa) and EQH (10 taxa). The effect of the area was also evident in SAR + HDH (five taxa) and EQH + HDH (one taxon), making it the prevailing driver in explaining S. Since distances are relatively short, and three out of four islands are land-bridge islands, the effect of distance was significant for 12 taxa. The effects of habitat diversity were evident for just nine taxa. The multi-taxon approach allowed us to understand the differential effect of drivers among taxa in influencing S in a single archipelago. Moreover, the multi-taxonomic rank approach highlighted how the information contained within higher taxonomic ranks (e.g., Division) can be substantially different from that derived from lower ranks (e.g., Family). These insights are of particular importance from a conservation perspective of the archipelago’s biodiversity, and this approach can be transferred to mainland fragmented systems.