Spatial Variation In Species Composition Research Articles

Decadal variation and temporal stability of the macrobenthic community in the Bohai Sea, China

Biodiversity in the Bohai Sea is threatened by climate change and human activities. An analysis based on decadal macrobenthic community data was conducted to assess the ecological health. These findings revealed the temporal and spatial variations in species composition and biodiversity, which were primarily influenced by depth, temperature and dissolved oxygen content. The community structure in 2014 exhibited a 70 % dissimilarity compared to other years, and biodiversity was lower in 2014. The dominant species showed a trend towards miniaturization. Abundance-biomass comparison curves indicated that community disturbance improved by implementing various policies. Overall, communities in the Bohai Sea remained stable, except in the Bohai Strait (BH), where synchronous fluctuations with an increasing trend were observed. Enhancing biodiversity and addressing the risks associated with losing single species are essential for maintaining community stability. The community also displayed synchronous tendencies in Laizhou Bay, emphasizing the need for continued long-term monitoring.

Spatiotemporal patterns of microclimatic buffering in relict alpine communities

AbstractQuestionsIn alpine landscapes, topography creates a mosaic of microclimatic niches that might prevent local extinctions, but the influence of this spatial heterogeneity on plant communities is largely unknown. Here we ask (1) how soil microclimatic variation is comparable at temporal and spatial scales, and (2) how such variation influences species composition and local extinctions in relict alpine communities.LocationPicos de Europa National Park, northern Spain.MethodsWe resurveyed permanent plots in four alpine sites following the recording of soil temperatures (temporal survey) for 10 years. We then sampled the spatial variation in species composition and microclimatic temperatures in 80 plots around the permanent plots (spatial survey). We evaluated the variation of six microclimatic indices between the temporal and the spatial surveys, and calculated the temporal trends observed in species cover. We finally predicted local extinction rates under microclimatic scenarios based on the observed microclimate–community relations.ResultsDespite high interannual variation, we found a 10‐year trend of temperature warming on (microridge) fellfields and (microvalley) snowbeds. Microclimatic variation was larger in space than in time, with little temperature variation in snowbeds and extreme low temperatures recorded in fellfields. Species composition was mainly influenced by growing degree days (GDD) and freezing degree days (FDD), which were both related to snow cover duration. Plant cover of 16 species (out of 36 frequent species) showed significant responses to microclimatic variation. Local extinctions were mainly predicted under relatively hotter and more freezing conditions.ConclusionsOur results support the idea that microclimatic spatial heterogeneity can reduce the negative influence of climate change on alpine plant communities. However, a continuous reduction of snow cover will result in a tipping point beyond which the buffer effect of this spatial heterogeneity will not be effective in protected microsites, leading to community homogenization. This process may have started in relict alpine communities where species from snowy microclimates are being outcompeted by species adapted to below‐zero winter temperatures.

Woody Plant Assemblages of Recently Declared Village Land Forest Reserve in The Eastern Afromontane Biodiversity Hotspot

Understanding of species composition of village land forest reserves and their driving factors informs adequate development of effective restoration strategies and sustainable forest management of miombo woodlands. This study assessed the effects of human disturbance as well as environmental variables on woody plant species composition using 24 square plots of 10 x 10 m in a recently declared village land forest reserve in the Eastern Afromontane biodiversity hotspot of Tanzania. Ordination analysis technique canonical correspondence analysis was used to identify important vegetation gradients and significant factors that explain the spatial variation in species composition of woody plants. Results showed that, 779 individual woody plants were recorded, of which 379 were seedlings (48.6%), 102 saplings (13.1%) and 298 adults (38.3%). The three most dominant plant species were Brachystegia spiciformis (42.2%), Diplorhynchus condylocarpon (9%) and B. boehmii (8.7%), while the least were Multidentia crassa and Diospyros squarrosa with each species having less than 1% overall abundance. Pterocarpus angolensis, a highly protected and near-threatened tree species, was also recorded but with only very few individuals. Canopy cover and soil pH were the two most important variables explaining the spatial variation in species composition of woody plants. These results emphasise that village forests are important for preserving native and threatened tree species, and improved management should discourage all practices that change natural conditions of canopy cover and soil pH to safeguard the remaining village forests, biodiversity and rural livelihoods.

Foundation species canopies affect understory beta diversity differently depending on species mobility.

Beta diversity measures the spatial variation in species composition. Because it influences several community attributes, studies are increasingly investigating its drivers. Spatial environmental heterogeneity is a major determinant of beta diversity, but canopy-forming foundation species can locally modify environmental properties. We used intertidal communities dominated by the canopy-forming alga Mazzaella laminarioides as a model system to examine how a foundation species affects spatial environmental heterogeneity and the resulting beta diversity. Since canopies were found to reduce the spatial variation of temperature and desiccation during low tides, we hypothesized that canopies would decrease understory beta diversity, which we tested through a field experiment that contrasted canopy removal with presence treatments over 32 months. The beta diversity of sessile species was always lower under canopies, but canopies never affected the beta diversity of mobile species. The observed responses for sessile species may result from their abundance being more dependent on spatial abiotic variation than for mobile species, which can occur in stressful areas while temporarily foraging or in transit to other areas. These responses may likely apply to other systems exhibiting canopy-forming foundation species hosting sessile and mobile species assemblages.

Two dominant forms of multisite similarity decline - Their origins and interpretation.

The number of species shared by two or more sites is a fundamental measure of spatial variation in species composition. As more sites are included in the comparison of species composition, the average number of species shared across them declines, with a rate increasingly dependent on only the most widespread species. In over 80% of empirical communities, models of decline in shared species across multiple sites (multisite similarity decline) follow one of two distinct forms. An exponential form is assumed to reflect stochastic assembly and a power law form niche-based sorting, yet these explanations are largely untested, and little is known of how the two forms arise in nature. Using simulations, we first show that the distribution of the most widespread species largely differentiates the two forms, with the power law increasingly favored where such species occupy more than ~75% of sites. We reasoned the less cosmopolitan distribution of widespread species within exponential communities would manifest as differences in community biodiversity properties, specifically more aggregated within-species distributions, less even relative abundance distributions, and weaker between-species spatial associations. We tested and largely confirmed these relationships using 80 empirical datasets, suggesting that the form of multisite similarity decline offers a basis to predict how landscape-scale loss or gain of widespread species is reflected in different local-scale community structures. Such understanding could, for example, be used to predict changes in local-scale competitive interactions following shifts in widespread species' distributions. We propose multiple explanations for the origin of exponential decline, including high among-site abiotic variation, sampling of highly specialized (narrow niche width) taxa, and strong dispersal limitation. We recommend these are evaluated as alternative hypotheses to stochastic assembly.

Spatial variation in ant–tree bipartite networks is driven by a bottom‐up process

Spatial shifts in the organisation and pattern of ecological networks may be driven by species composition turnover, changes in species abundance and/or abiotic effects on species interactions. To test the above assumptions, we collected arboreal ants and recorded host tree species from five latitudinal sites in Xishuangbanna, China. We constructed bipartite networks and compared spatial variation in species composition, interactions and stability change. We also analysed the relationship between network structure metrics and network stability. Results showed that ant composition differed significantly among the five sites, primarily determined by weaver ants (Oecophylla smaragdina) and Crematogaster ant species. Dominant tree species included Ficus (32 individuals), Hevea (14 individuals), Castanopsis (11 individuals) and Pittosporopsis (8 individuals). Ant richness was positively correlated with tree richness, suggesting that host trees support ant diversity as a fundamental environment. The ant–tree bipartite networks showed low connectance, high specificity and low niche overlap. Links per species and network node were positively correlated with network stability, whereas connectance, nestedness, specificity and niche overlap were not. Ants and trees formed a nonspecific and sparse bipartite network, and the number of nodes and links per species promoted network stability. Because plant richness was positively related to ant richness, and because arboreal ants feed predominantly on extrafloral nectaries, seeds, insects and honeydew secreted from hemipteran insects, we believe the bottom-up process plays a central role in determining ant–tree interaction networks.

Beta Diversity of Antarctic and Sub-Antarctic Benthic Communities Reveals a Major Role of Stochastic Assembly Processes

Community assembly is the result of both, deterministic and stochastic processes. The former encompasses niche-based local-scale mechanisms such as environmental filtering and biotic interactions; the latter includes ecological drift, probabilistic colonisation, and random extinctions. Using standardised sampling protocols, we show that the spatial variation in species composition (beta diversity) of shallow subtidal macrobenthic communities of sub-Antarctic (Strait of Magellan and Yendegaia Fjord [Beagle Channel]) and Antarctic (Fildes Bay [King George Island, West Antarctic Peninsula]) localities reflects a high contribution of stochastic processes to community assembly. Null model analyses indicated that random sampling from species pools of different sizes drove the observed among-locality differences in incidence- and abundance-based beta diversity. We analysed a normalised stochasticity ratio (NST), which delimits between more deterministic (<50%) and more stochastic (>50%) assembly. NST was notably larger than 50%, with mean values of 69.5% (95% CI = 69.2–69.8%), 62.5% (62.1–62.9%), and 72.8% (72.5–73.2%) in Strait of Magellan, Yendegaia Fjord, and Fildes Bay, respectively. Accordingly, environmental factors, such as depth, seawater temperature, salinity, and underwater light penetration, accounted for a small fraction of the spatial variation in community composition across the three localities. In this region, therefore, stochastic processes could have stronger effects on community assembly than deterministic niche-based factors. As anthropogenic biotic homogenisation continues apace, our study can give useful insights into the major ecological processes in Southern Ocean’ coastal marine communities.

Tree species diversity mapping using UAS-based digital aerial photogrammetry point clouds and multispectral imageries in a subtropical forest invaded by moso bamboo (Phyllostachys edulis)

Moso bamboo (Phyllostachys edulis) tends to invade any surrounding forest areas due to its aggressive characteristics (fast growth and clonal reproduction), where it changes the species composition and canopy structure of the forests, and has negative effects on forest diversity and ecosystem functions. Unmanned aerial system (UAS)-based remote sensing has the capacity to provide high-resolution, continuous spatial data that can be used to detect forest invasion dynamics. In this study, UAS-based RGB and multispectral image data and digital aerial photogrammetric point cloud (PPC) were acquired and used to detect areas of bamboo invasion in a subtropical forest of Southern China. First, a point cloud segmentation (PCS) method was applied for individual tree detection (ITD) using photogrammetric point clouds (PPCs). A random forest (RF) classifier was used to perform tree species classification based on PPC metrics, vegetation indices, and texture metrics. Finally, based on the results of the ITD and tree species classification, alpha-diversity (i.e., the species richness (S), Shannon-Wiener (H’), Simpson (D), and Pielou’s evenness index(J)) and the spatial variation in species composition along the altitude gradient (beta-diversity) in the invaded forests were assessed. Results demonstrated that PCS worked well for tree detection in invaded forests (F1-score = 80.63%), and the overall accuracy of tree species classification was 75.69%, with a kappa accuracy of 73.76%. The forest diversity analysis showed that all alpha-diversity values were generally predicted well (R2 = 0.84–0.91, RMSE = 0.05–0.84). The diversity showed a decreasing tendency with increasing bamboo invasion, and the predominantly broad-leaved invaded forests had higher diversity than the predominantly coniferous invaded forests. The human intervention had a significant impact on bamboo invasion. The ANOVA of the dispersion of the dissimilarities along the elevation gradient showed significant differences in abundance-weighted similarity among the altitude classes (ANOVA of the Bray-Curtis dissimilarity, F4,40 = 6.453, P = 0.0004***; ANOVA of the Jaccard dissimilarity, F4,40 = 5.20, P = 0.0017**). This study indicated the potential benefits of using UAS- based remote sensing data to identify tree species and predict forest diversity in bamboo-invaded forests. Our results suggested that tree species diversity can be directly estimated using individual tree detection results based on PPC data instead of modelling the relationship between field-measured indices and remote sensing data-derived metrics, and revealed the influence of human intervention on bamboo invasion.

Assemblage reorganization of South African dragonflies due to climate change

AbstractAimClimate change is expected to cause large shifts in species assemblages such as dragonflies and damselflies (Insecta: Odonata). Here, we assess the influence of environmental drivers of turnover on Odonata assemblages. Secondly, we map the predicted spatial variation in species composition, first as a gradient of assemblage similarity, and then as discrete bioregions delineating major areas of odonate endemism. Finally, we map the magnitude of expected change in species turnover in response to climate change under two emission scenarios.LocationSouth Africa.MethodsWe used a spatial database comprising of 164 species of odonates and 20 covariates, to explore changes in compositional turnover using generalized dissimilarity models. Bioregions were compiled through various clustering techniques.ResultsPresent‐day odonate bioregions correspond to climatic zones and are clearly separated by transitional zones with rapid spatial turnover. Present odonate bioregions are projected to undergo extensive reorganization by 2050 and 2070. Temporal turnover in species composition is expected to reach up to 80% in the large arid interior and 64% along the coast. Half of all South Africa's protected areas are likely to experience climate induced changes to dragonfly bioregions in the near future.Main conclusionsSpecies assemblages are rapidly changing. This work highlights future shifts in climate will result in complex and nonlinear responses in Odonata communities. With ongoing climate change, current odonate bioregions are predicted to expand while others will contract considerably in size within the next 30 years. The current demarcated protected areas may be inadequate to protect dragonflies as climates change. Odonata can be used to track forefronts of climate change, which will likely affect a larger array of taxa as well.

Temporal changes in spatial variation: partitioning the extinction and colonisation components of beta diversity.

The last two decades have witnessed unprecedented changes in beta diversity, the spatial variation in species composition, from local to global scales. However, analytical challenges have hampered empirical ecologists from quantifying the extinction and colonisation processes behind these changing beta diversity patterns. Here, we develop a novel numerical method to additively partition the temporal changes in beta diversity into components that reflect local extinctions and colonisations. By applying this method to empirical datasets, we revealed spatiotemporal community dynamics that were otherwise undetectable. In mature forests, we found that local extinctions resulted in tree communities becoming more spatially heterogeneous, while colonisations simultaneously caused them to homogenise. In coral communities, we detected non-random community disassembly and reassembly following an environmental perturbation, with a temporally varying balance between extinctions and colonisations. Partitioning the dynamic processes that underlie beta diversity can provide more mechanistic insights into the spatiotemporal organisation of biodiversity.

Unraveling the drivers of plant taxonomic and phylogenetic β-diversity in a human-modified tropical dry forest

Biodiversity maintenance in human-modified landscapes largely depends on spatial variations in species composition (β-diversity), but the impact of human disturbance on β-diversity remains poorly understood. We examined how taxonomic and phylogenetic β-diversity of woody plant communities in the Brazilian Caatinga dry forest respond to two emerging threats—chronic anthropogenic disturbance and water scarcity. We separately assessed diversity metrics that give a disproportionate weight to rare species, and metrics weighted by dominant species. We recorded a total of 5118 individuals from 104 species across 19 0.1-ha plots into a 21,430-ha human-modified landscape exposed to chronic disturbances and a high variation in climatic water deficit. At the landscape scale, β-diversity was higher when considering rare species than when focusing on dominant species, especially for the phylogenetic dimension of β-diversity. Water deficit was the primary driver of plant taxonomic and phylogenetic β-diversity, followed by the number of cattle and inter-site isolation; however, rare species seem to depend more strongly on these factors than the dominant ones. Therefore, preserving as much forest as possible, including areas exposed to different disturbance level and climate variables, is critical to prevent the loss of rare species and maintain the compositional differentiation of biotic assemblages. Such forest cover should be maintained in a large number of forest patches scattered through the landscape to preserve biologically and functionally distinct components of this ecosystem, avoid landscape-scale biotic homogenization, and thus favor its ecological resilience.

Acoustic monitors and direct observations provide similar but distinct perspectives on bird assemblages in a lowland forest of eastern Ecuador.

Bird communities in lowland Neotropical forests exhibit temporal and spatial variation in species composition and abundance at multiple scales. Detecting and explaining such variation requires adequate methods for sampling those bird communities but counting birds in highly diverse lowland forests of the Neotropics can be particularly challenging. Point counts are one of the most frequently used methods for counting birds in tropical forests but inter- and intra-observer variability in detecting and identifying sounds may cause problems. Acoustic monitors (passive acoustic monitors; autonomous recording units) provide an alternative and potentially effective method to sample bird communities by acting, in effect, as “point counts”, recording vocalizations at a given point for a set time. I used acoustic monitors to examine patterns of species richness, spatial distribution, and community composition of birds in a lowland forest in eastern Ecuador, one of the most diverse regions on earth. I deployed monitors at 25 locations, each separated by at least 200 m, on each of two 100-ha plots (Harpia, Puma) at Tiputini Biodiversity Station during January–February, 2013–2017. Monitors were set to record for 10 min followed by a 5-min break, from 0545 h to 0810 h (10 recording periods/morning). Recordings were later reviewed to identify species; no attempt was made to distinguish individuals or to estimate distance. Results were compared with contemporaneous direct observations along transects on the same plots. A total of 214 species were identified from recordings on both plots, combined, with slightly more on Harpia (208) than on Puma (188). Number per year ranged from 142 on Harpia in 2016 to 161 on Puma in 2015. Number per point was ~45 with an overall range of 29–68. Number of species detected in recordings was similar to but somewhat less than the number recorded during direct observations. Number of species recorded increased rapidly from the first period (0545–0555 h) to the third (0615–0625 h) but showed little subsequent change. Most species were recorded at relatively few points; the four most widely distributed species were the same on both plots (Patagioenas plumbea, Xiphorhynchus guttatus, Capito aurita, Ramphastos tucanus), all of which are relatively loud canopy or subcanopy species. Ordinations based on species composition illustrated differences between plots based on both recordings and direct observations; similarly, patterns of species composition differed between methods. Acoustic monitors can be an effective tool for sampling bird communities and may be particularly effective and efficient for sampling loud species with distinctive songs. Nonetheless, results from monitors may provide different perspectives on species composition when compared to direct observations. Which method is preferred likely will depend on the specific objectives of individual studies.

<p><strong>Diversity partitioning and community structure of epiphytic bryophytes along an elevational gradient in the north-eastern Madagascar</strong></p>

Understanding spatial variation in species composition of different communities is key to understanding the processes that generate and maintain biodiversity. The partitioning of diversity into hierarchical scale-related components is an interesting approach to quantitatively defining the overall net biodiversity from hierarchically scaled studies and is a useful method in studies of conservation biology and restoration. This paper deals with the additive partitioning of the overall diversity and the partitioning of beta-diversity of epiphytic bryophytes along an elevational gradient in Madagascar. The aim is to describe the variation in species composition between sites and to elucidate why different species occur in different communities in the Marojejy National Park (250–2050 m). We looked at the contribution of α and β diversity to total diversity were calculated from four hierarchical scales: microhabitat (50 cm2), quadrat (4 m2), plot (100 m2) and elevation (every 200 m). Furthermore, we documented how the two components of beta-diversity (turnover and nestedness) are influenced by variation in elevation. Our result suggests that more variation in species richness was found within the elevational scales, than within microplot scales, confirming that beta diversity at the largest sampling scale is the largest contributor to the total diversity. It indicates that bryophyte species among sample within each level are a subsample of the same species pool. This study shows evidence that the beta-diversity of epiphytic bryophyte assemblages is dominated by high spatial turnover due to recruitment of new species along the Marojejy transect, a clear pattern for mountains.

Partitioning the colonization and extinction components of beta diversity across disturbance gradients.

Changes in species diversity often result from species losses and gains. The dynamic nature of beta diversity (spatial variation in species composition) that derives from such temporal species turnover, however, has received relatively little attention. Here, we disentangled extinction and colonization components of beta diversity by using the sets of species that went locally extinct and that newly colonized the study sites. We applied this concept of extinction and colonization beta diversity to ground vegetation communities that have been repeatedly surveyed in forests where fire and harvesting were experimentally applied. We first found that fire and harvesting caused no effect on beta diversity 2 yr after the treatments. From this result, we might conclude that they did not alter the ways in which species assemble across space. However, when we analyzed the extinction and colonization beta diversity between pre-treatment and 2 yr after the treatments, both measures were found to be significantly lower in burned sites compared to unburned sites (i.e., the groups of excluded and newly colonized species both showed low beta diversity in the burned sites). These results indicate that the fire excluded similar subsets of species across space, making communities become more heterogeneous, but at the same time induced spatially uniform colonization of new species, causing communities to homogenize. Consequently, the effects of these two processes canceled each other out. The relative importance of extinction and colonization components per se also changed temporally after the treatments. Fire and harvesting showed synergetic negative impacts on extinction beta diversity between pre-treatment and 10 yr after the treatments. Overall, analyses using extinction and colonization beta diversity allowed us to detect nonrandom disassembly and reassembly dynamics in ground vegetation communities. Our results suggest that common practices of analyzing beta diversity at one point in time can mask significant variation driven by disturbance. Acknowledging the extinction-colonization dynamics behind beta diversity is essential for understanding the spatiotemporal organization of biodiversity.

Forested riparian belts as reservoirs of plant species in fragmented landscapes of tropical mountain cloud forest

Background: Cloud forest in central Veracruz is highly fragmented. However, different arboreal elements are still present within the agricultural matrix, including small patches of secondary forest, isolated trees and forested riparian belts. These elements could be important for cloud forest species conservation.
 Questions: What is the structure and composition of forested riparian belts within current anthropic landscapes, and what is their potential contribution as reservoirs of mountain cloud forest native plant species?
 Studied species: Vegetation community of forested riparian belts of cloud forest.
 Study site and dates: Eastern Mexico (central Veracruz), January to November 2018
 Methods: Along 14 segments of riparian belts (?400 m long), distributed across different tributary streams, six 50 × 2 m transects were placed (three per riverside) per segment. Every plant rooted within a transect and ? 1.5 m in height was identified and measured (height and DBH).
 Results: A total of 2,062 plants from 161 species, 102 genera and 55 families were recorded in the 14 sites (8,400 m² sampled). Structural attributes and floristic composition varied widely amongst sites. Elevation and the amount of forest cover (i.e., area) within 500 m of each sampling site were the most important factors underlying the spatial variation in species composition.
 Conclusions: Riparian belts were remarkably heterogeneous harboring a notable richness of tree and shrub species many of them native of the original cloud forest. This diversity reveals that these arboreal elements are keystone structures for biodiversity conservation and also have a high potential as propagule sources for cloud forest restoration in anthropic landscapes.

Taxonomic and phylogenetic diversity patterns in the Northern Sporades islets complex (West Aegean, Greece)

The Aegean archipelago has long been the main research area of numerous biogeographers, plant ecologists and taxonomists due to its intricate palaeogeography and high environmental and topographical heterogeneity. Nevertheless, some parts of this archipelago are essentially unexplored and the processes driving spatial variation in species composition remain unaddressed. Aiming to fill these gaps, we investigated the flora and plant diversity patterns of the Northern Sporades island group, as well as its biogeographical relationships. The study area lies in the biogeographical region of the West Aegean islands and comprises 23 islands and islets. The total flora of the study area consists of 1202 infrageneric taxa, belonging to 517 genera and 120 families, reflecting its geographical and bioclimatic characteristics. The endemic element consists of 41 taxa (3.4% of the flora), eight of which are restricted to the West Aegean islands and two are single island endemics. Area emerged as the most important variable in shaping plant species richness, while niche-based processes played a lesser role in driving these patterns. Regarding the taxonomic and phylogenetic beta-diversity patterns, environmental filtering and not dispersal limitation seems to shape the plant assemblages of the Northern Sporades islets. Biogeographically, the Northern Sporades island group seems to be closer connected to the Kiklades rather than to Evvia or the adjacent mainland, due to their longer isolation and separate palaeogeographical history during the Quaternary.

Beta diversity patterns of Bromeliaceae growing on rocky cliffs within the Atlantic Forest in southern Brazil

Abstract: In recent years there has been increasing attention in patterns of β-diversity and mechanisms related to variations in species composition. In this study, we evaluated beta diversity patterns of bromeliads growing on cliffs immersed in Atlantic Forest. We hypothesized that the species composition varies according to the spatial scale, inferring that there is a replacement of species influenced mainly by environmental factors. The study was carried out on sandstone cliffs included in contiguous but distinct vegetation formations: Evergreen and Seasonal forests. Twenty-four vertical rocky outcrops were sampled. The spatial variation in species composition was evaluated by two β-diversity components, turnover and nestedness. Multivariate analysis and variation partitioning were performed to distinguish niche and stochastic processes. We recorded 26 bromeliad species and a significantly higher contribution of turnover explaining beta diversity. Environmental factors affect β-diversity patterns of Bromeliaceae. However, individually, the environmental predictors do not explain the data variation. Environmental variations spatially structured, and spatial variables determinate the dissimilarity in the composition of bromeliads on cliffs. Thus, our results revealed that both environmental and spatial effects can act together to define the floristic composition of rock-dwelling bromeliad communities.

Wilderness areas halve the extinction risk of terrestrial biodiversity.

Reducing the rate of global biodiversity loss is a major challenge facing humanity1, as the consequences of biological annihilation would be irreversible for humankind2-4. Although the ongoing degradation of ecosystems5,6 and the extinction of species that comprise them7,8 are now well-documented, little is known about the role that remaining wilderness areas have in mitigating the global biodiversity crisis. Here we model the persistence probabilityof biodiversity, combininghabitat condition with spatial variation in species composition, to show that retaining these remaining wilderness areas is essential for the international conservation agenda. Wilderness areas act as a buffer against species loss, as the extinction risk for species within wilderness communities is-on average-less than half that of species in non-wilderness communities. Although all wilderness areas have an intrinsic conservation value9,10, we identify the areas on every continent that make the highest relative contribution to the persistence of biodiversity. Alarmingly, these areas-in which habitat loss would have a more-marked effect on biodiversity-are poorly protected. Given globally high rates of wilderness loss10, these areas urgently require targeted protection to ensure the long-term persistence of biodiversity, alongside efforts to protect and restore more-degraded environments.

Epiphytic diatoms as bioindicators of trophic status of Lake Modrac(Bosnia and Herzegovina)

Biodiversity of diatoms and applicability of diatom indices in biomonitoring based on littoral epiphytic samples of Lake Modrac were investigated. Diatoms were taken mostly from Phragmites australis stems in 2017, during which physical and chemical parameters of the water were measured. A total of 85 diatom taxa were identified. Gomphonema (13 spp.), Navicula (11 spp.), and Nitzschia (8 spp.) were the most abundant genera. Obtained values of trophic indices (TID, TvD, and TDIL) pointed to meso- to eutrophic status for most localities, while values of the IBD, EPI, ?D, and IPS indices indicated good ecological status, except for localities at the mouth of 2 main tributaries which had moderate or poor ecological status. Based on the hierarchical group average clustering and nonmetric multidimensional scaling, 4 groups were identified, mainly related to the sampling period, with higher spatial variation in species composition during summer. Since environmental legislation in Bosnia and Herzegovina still does not provide detailed instructions on using diatoms in biological assessment, results of this study can be useful for the development of biomonitoring tools for lakes in Bosnia and Herzegovina.

A framework for disentangling ecological mechanisms underlying the island species–area relationship

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.