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Biological soil crusts (biocrusts) are key contributors to desert ecosystem functions, therefore, biocrust restoration following mechanical disturbances is imperative. In the Negev Desert hyperarid regions, phosphate mining has been practiced for over 60 years, destroying soil habitats and fragmenting the landscape. In this study, we selected one mining site restored in 2007, and we used DNA stable isotope probing (DNA-SIP) to identify which bacteria grow in post-mining and adjacent natural biocrusts. Since biocrust communities activate only after wetting, we incubated the biocrusts with H218O for 96 h under ambient conditions. We then evaluated the physicochemical soil properties, chlorophyll a concentrations, activation, and functional potential of the biocrusts. The DNA-SIP assay revealed low bacterial activity in both plot types and no significant differences in the proliferated communities' composition when comparing post-mining and natural biocrusts. We further found no significant differences in the microbial functional potential, photosynthetic rates, or soil properties. Our results suggest that growth of hyperarid biocrust bacteria after wetting is minimal. We hypothesize that due to the harsh climatic conditions, during wetting, bacteria devote their meager resources to prepare for the coming drought, by focusing on damage repair and organic compound synthesis and storage rather than on growth. These low growth rates contribute to the sluggish recovery of desert biocrusts following major disturbances such as mining. Therefore, our findings highlight the need for implementing active restoration practices following mining.

Species diversity-productivity relationship is often, but not always, scale dependent. We hypothesize that the arrangement of environmental heterogeneity along a rainfall gradient, as a surrogate for productivity, determines whether scale dependence of beetle diversity at our sandy sites exists. We chose seven geographically distant landscapes (360 kms from south to north) within a mean annual rainfall range of 30–585 mm, each having six clusters of five uniformly distributed pitfall traps (within a range of 0.24 km2). Vegetation and physical variables were measured within each landscape and its clusters to characterize both spatial and temporal heterogeneity. We used species diversity of each cluster and the accumulative species diversity in a landscape as local and regional diversity, respectively. Between-clusters dissimilarity in diversity reflected the turnover of species within a landscape. We used environmental measures in each cluster and at the entire landscape to indicate local and regional heterogeneity, respectively, and changes between transects to characterize the within-landscape dissimilarity in heterogeneity. Beetle diversity and productivity showed a unimodal pattern at both spatial scales, with a peak at intermediate productivity of ca. 300 mm. Environmental heterogeneity increased with productivity both at the local and at the landscape scales, but within-landscape dissimilarity in heterogeneity did not change with productivity. Between-clusters dissimilarity in diversity was higher at intermediate productivity, explaining the unimodal pattern at the landscape scale. We suggest that the scale independence in our study results from the equal distribution of environmental heterogeneity within a landscape. We propose that the exploration of the diversity-productivity relationship across scales should consider the way heterogeneity is distributed along the productivity gradient.

Studying biodiversity in light of increased fragmentation in agroecosystems requires the understanding of scale-dependent and multi-scale determinants of various community measures. In a heterogeneous agro-landscape, we aimed to understand whether: (1) Reptile communities are affected by a certain variable that belongs to a particular scale, or, by a combination of variables at different scales, and (2) Reptile community measures are affected differentially by variables related to different scales. We sampled reptiles in three 12.6 km2 land units by using 100 × 50 m plots within 27 natural habitat patches. We collected spatial information of different scale-oriented physical and biotic variables and analyzed changes in community measures at four scales—landscape, land unit, patch and plot—by using the model selection approach based on the AICc. Multiple-scale, rather than single-scale models, best explained all three community measures, indicating that the reptile community structure is highly affected by ecological processes operating at different scales, from the local up to the entire landscape scale. However, abundance, species richness and diversity were affected dissimilarly by different combined determinants and at different scales. Reptile biodiversity at our heterogenous agro-landscape is highly influenced by determinants of multiple scales, where each scale has its contribution to the overall obtained pattern. Number of individuals and species richness respond differently to various processes, depending on the scale at which these processes operate. Agro-landscapes retain the complexity of ecological systems and can serve to maintain natural communities through land sharing practices.

Context Intensive use of agricultural land often modifies the landscape by dividing continuous natural habitat into smaller and more isolated patches. While it is widely recognized that landscape fragmentation is a main cause of species extinction, less is known about how this impacts the function of organisms that do persist in the modified environment. Understanding these effects is complicated by the fact that fragmentation can affect organisms directly but also indirectly, by altering the patch microclimatic conditions. Objectives We tested the hypothesis that fragmentation-induced microclimate change might be an important mechanism driving changes in animal locomotion in an agricultural landscape. Methods We used satellite image analysis, behavioral assays, and patch analyses, to disentangling the direct and indirect effects of fragmentation on the locomotor behavior of a darkling beetle, Zophosis punctata (Tenebrionidae), in the Southern Judea Lowlands in Israel. Results We found that fragmentation in an agricultural ecosystem may lead to changes in the thermal conditions of natural habitat patches. Importantly, such fragmentation-related increases in patch temperature played an important role in explaining variation in beetle locomotion across an agricultural landscape. Specifically, beetles from highly fragmented landscapes, which included warmer habitat patches, showed high locomotor intermittence –frequent pausing events during locomotion. Conclusions This study shows that the potential consequences of landscape fragmentation on the organism function are likely to be underestimated when fragmentation-related microclimate change is ignored. Intermittent locomotion, as opposite to steady locomotion, may provide various physiological and fitness benefits in fragmented landscapes, like mitigating performance limitations imposed by extreme thermal conditions.

Mining contributes significantly to economic development, but it also entails extensive environmental damage, such as soil degradation and water and air pollution. Mining activity impacts the soil quality, often making it unable to support ecosystem function and structure. The current study aims to apply the soil quality index (SQI) as a methodology for quantifying soil restoration status in an open-pit phosphate mine in Israel’s hyper-arid environment. In this regard, we evaluated an ecological restoration practice that includes topsoil refilling compared to the adjacent undisturbed natural system, using transformed and standardized scorings of 11 physical, biological, and chemical soil properties that were further statistically integrated into overall SQI values. Our results revealed significant differences between the restoration practice areas and the nearby natural areas, with a higher soil quality value in the latter. It is proposed that the topsoil restoration method is mainly affected by soil biological indicators, such as soil organic matter, soil proteins, and polysaccharides related to micro-organic growth, and in a lesser extent, by physical properties (primarily infiltration rate, followed by AWC). The former properties encourage the biocrust establishment, which is essential for soil surface stabilization and affects the water infiltration rate and nutrient availability. The chemical indicators showed no significant differences between most of the sites for the overall soil quality. In conclusion, soil properties, primarily physio-biological ones, should be selected to quantify and evaluate restoration practices in hyper-arid ecosystems.

Biocrusts are key ecosystem engineers that are being destroyed due to anthropogenic disturbances such as trampling, agriculture and mining. In hyper-arid regions of the Negev Desert, phosphate has been mined for over six decades, altering the natural landscape over large spatial scales. In recent years, restoration-oriented practices were mandated in mining sites, however, the impact of such practices on the ecosystem, particularly the biocrust layer, has not been tested. Here, we evaluated post-mining biocrust bacterial communities and compared them to undisturbed (reference) biocrusts. We collected samples from four mining sites (each restored at a different year) and their corresponding reference sites. We hypothesized that post-mining bacterial communities would differ significantly from reference communities, given the slow regeneration of the biocrust. We also hypothesized that bacterial communities would vary among post-mining plots based on their restoration age. To test these hypotheses, we assessed the abundance and diversity of bacterial communities by sequencing the 16S rDNA and their photosynthetic potential by quantifying the abundance of cyanobacteria and chlorophyll a. The bacterial diversity was lower, and community composition differed significantly between post-mining and reference biocrusts. In addition, cyanobacteria abundances and chlorophyll a content were lower in post-mining biocrusts, indicating lower photosynthetic potential. However, no significant changes in bacterial communities were detected, regardless of the restoration age. We suggest that the practices implemented in the Negev mines may not support the recovery of the biocrust bacterial communities, particularly the cyanobacteria. Thus, active restoration measures are needed to accelerate the regeneration time of biocrusts at the hyper-arid Negev mines.

Agriculture poses a threat upon wildlife worldwide and particularly to reptiles. However, the effects of many crop types on reptile diversity remain unknown. In this field study, we examined the local effects of two understudied common crop types in Mediterranean regions, intensively cultivated vineyards and intensified-traditional olive plantations, on reptile diversity patterns. We compared measurements of diversity among an array of study plots representing each crop as well as plots in adjacent patches of natural habitat. We developed a new index, the Average Specialization Index, in order to compare the degree of habitat-specialization of the species in the different habitats. Among the habitat types examined, the natural patches were the most structurally heterogeneous and contained the greatest species richness and diversity. In contrast, the intensive vineyards were structurally homogeneous and were uninhabitable areas for reptiles. The more-traditionally cultivated olive plantations were intermediately heterogeneous and provided a unique habitat occupied by a community with a high proportion of reptile species considered to be habitat specialists. Despite showing high abundance and eveness, the reptile community within the olive plantations still contained a lower species richness and diversity compared to natural patches. In light of our results, we recommend implementing a more wildlife-friendly management strategy in landscapes converted to agricultural cultivation.

To understand patterns of alpha, beta and gamma diversities in fragmented landscapes we need to explore the three scale components in relation to potential drivers in a scale-dependent manner. Often, the drivers themselves can be partitioned to alpha, beta and gamma diversities. Thus, one can hypothesize that the scale-components of species diversity and drivers’ diversity match, i.e., that species alpha diversity is mainly explained by drivers’ alpha diversity, beta by beta and gamma by gamma. Here, we explore this ‘scale-matching’ hypothesis for spiders in two fragmented agricultural landscapes. In each landscape, we sampled spiders and their potential prey in 12 patches. Then, we sub-sampled pseudo-landscapes in which we calculated spider alpha, beta and gamma diversities using multiplicative diversity-partitioning. Next, we used variance partitioning analysis to explore the relative contribution of eleven explanatory variables from five thematic groups (sampling intensity, area, connectivity, habitat diversity and prey diversity), while further partitioning the habitat and prey diversities to their corresponding alpha, beta and gamma diversities. We found considerable evidence for scale-matching, with spiders’ alpha and beta diversities explained mostly by the corresponding alpha and beta diversities (respectively) of prey and/or habitat. We further found a strong effect of connectivity on spider beta diversity, but not on alpha and gamma diversities. For spiders gamma diversity, a cross-scale effect was observed. Our results suggest that multiple drivers from multiple scales interact in structuring patterns of spider alpha, beta and gamma diversities in agro-ecosystems, yet the strongest effects are of those drivers that match in scale.

Associated data is available at: https://doi.org/10.5061/dryad.595718c; International audience; Habitat destruction is the single greatest anthropogenic threat to biodiversity. Decades of research on this issue have led to the accumulation of hundreds of data sets comparing species assemblages in larger, intact, habitats to smaller, more fragmented, habitats. Despite this, little synthesis or consensus has been achieved, primarily because of non-standardized sampling methodology and analyses of notoriously scale-dependent response variables (i.e., species richness). To be able to compare and contrast the results of habitat fragmentation on species’ assemblages, it is necessary to have the underlying data on species abundances and sampling intensity, so that standardization can be achieved. To accomplish this, we systematically searched the literature for studies where abundances of species in assemblages (of any taxa) were sampled from many habitat patches that varied in size. From these, we extracted data from several studies, and contacted authors of studies where appropriate data were collected but not published, giving us 117 studies that compared species assemblages among habitat fragments that varied in area. Less than one-half (41) of studies came from tropical forests of Central and South America, but there were many studies from temperate forests and grasslands from all continents except Antarctica. Fifty-four of the studies were on invertebrates (mostly insects), but there were several studies on plants (15), birds (16), mammals (19), and reptiles and amphibians (13). We also collected qualitative information on the length of time since fragmentation. With data on total and relative abundances (and identities) of species, sampling effort, and affiliated meta-data about the study sites, these data can be used to more definitively test hypotheses about the role of habitat fragmentation in altering patterns of biodiversity. There are no copyright restrictions. Please cite this data paper and the associated Dryad data set if the data are used in publications.

Landscape heterogeneity is a general feature of natural environments, strongly affected by habitat fragmentation. It can affect a population's dynamics and probability of extinction. Fragmentation increases among-patch isolation and decreases patch size, resulting in a reduction in available resources in smaller patches. To persist, animals must be able to translate the variation imposed by fragmentation into adaptive energy allocation strategies that enable populations to avoid extinction. This means that physiological adaptations are expected to reflect changes in landscape configuration, especially in the size of the natural habitat patches and degree of isolation among them. We propose a novel, integrative conceptual framework in which spatial characteristics of the environment, imposed by fragmentation, lead to specific life-history traits that increase survival (at the individual level) and decrease the likelihood of extinction (as an emergent property at the population level). We predict that a resource allocation trade-off between the life-history traits of reproduction and dispersal along a fragmentation gradient will emerge. Populations occurring in patches of different sizes and isolations along gradients of fragmentation and productivity will exhibit differences in the strength of the dispersal-reproduction trade-off. Emerging from this framework are several explicit and testable hypotheses that predict that the dispersal-reproduction trade-off will be shaped by landscape heterogeneity imposed by fragmentation. Hence, this trade-off serves as the mechanistic link that translates environmental variation created by fragmentation into variation in species abundances and population dynamics by lowering local extinction probability and increasing overall population persistence.

Land sharing strategies in agricultural landscapes need to allow for organisms to move between natural areas and different crops within an agro-ecological landscape in order to reduce extinction probability and the negative effects of small isolated populations. In this study, we tested whether legume or wheat fields differed in their effects on reptiles’ movement patterns. We conducted our study in an agro-ecosystem consisting of small isolated natural habitat patches nested within agricultural fields. We trapped reptiles in sampling arrays before and after harvest in both wheat and legume fields, and in adjacent natural habitat patches. For both crops, prior to harvest, we found an increase in movements of Trachylepis vittata, the most common reptile in our study, from the natural habitat patches into fields, but negligible movement in the opposite direction. In both crops before harvest, the individuals that moved into the fields were adults of better body condition than those remaining in the natural habitat patch, suggesting that long-distance movements were only possible for individuals with high prospective fitness. After harvest, no movements were documented between wheat fields and natural habitat patches. However, in legume fields, a high symmetrical movement (i.e. in both directions) of individuals of similar body condition between fields and natural habitat patches took place. Importantly, newborn lizards were only found in the natural habitat patches and in post-harvest legume fields. Our results suggest that agricultural heterogeneity, through a mixture of crop types may mitigate some of the negative effects of particular crops on biodiversity. As crop rotation between wheat and legume fields is common worldwide, our findings highlight the importance of creating an agricultural mosaic to enhance biodiversity permeability within the agricultural matrix.

This is the first population genomic analysis that examines micro-evolutionary changes in co-occurring plant species, in fragmented habitats, along a precipitation gradient. We applied Genotype-by-Sequencing (GBS) on three different annual Asteraceae on the same sites that share similar life history strategies, but different pollination and dispersal strategies (Catananche lutea, Geropogon hybridus, Urospermum picroides). We tested if the genetic diversity for all species correlates with effective population sizes along the precipitation gradient and whether therefore genetic drift drives evolution at range edges. However, our results support this hypothesis for only one species (C. lutea) but refute it for the other two. Potential genomic signals of adaptation to the high precipitation gradient were found only in one species (U. picroides). We also tested if species with complex pollination and diversified dispersal strategies are less affected by small scale habitat fragmentation, but the opposite is true. Biological differences between the species studied (pollination and dispersal) explain population genetic differences along the precipitation gradient at range edges rather than environmental filters. Pairwise correlation analyses showed no or only weak similarities in the accumulation of mutations in the different species. Our results suggest that the processes driving evolution in different co-occurring species are different, so that most genomic similarities in our investigations may only represent temporary stages in evolution.

GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (relevés) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001; ... 1,000 m²) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetation-plot databases, such as the European Vegetation Archive (EVA) and the global database “sPlot”. Its main aim is to facilitate studies on the scale- and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board. Abbreviations: EDGG = Eurasian Dry Grassland Group; EVA = European Vegetation Archive; GrassPlot = Database of Scale-Dependent Phytodiversity Patterns in Palaearctic Grasslands; SAR = species-area relationship.

Aim Although species-occupancy distributions (SODs) and species-area relationships (SARs) arise from the two marginal sums of the same presence/absence matrices, the two biodiversity patterns are usually explored independently. Here, we aim to unify the two patterns for isolate-based data by constraining the SAR to conserve information from the SOD. Location Widespread. Methods Focusing on the power-model SAR, we first developed a constrained form that conserved the total number of occupancies from the SOD. Next, we developed an additive-constrained SAR that conserves the entire shape of the SOD within the power-model SAR function, using a single parameter (the slope of the endemics-area relationship). We then relate this additive-constrained SAR to multiple-sites similarity measures, based on a probabilistic view of Sorensen similarity. We extend the constrained and additive-constrained SAR framework to 23 published SAR functions. We compare the fit of the original and constrained forms of 12 SAR functions using 154 published data sets, covering various spatial scales, taxa and systems. Main conclusions In all 23 SAR functions, the constrained form had one parameter less than the original form. In all 154 data sets the model with the highest weight based on the corrected Akaike's information criteria (wAICc) had a constrained form. The constrained form received higher wAICc than the original form in 98.79% of valid pairwise cases, approaching the wAICc expected under identical log-likelihood. Our work suggests, both theoretically and empirically, that all SAR functions may have one unnecessary parameter, which can be excluded from the function without reduction in goodness-of-fit. The more parsimonious constrained forms are also easier to interpret as they reflect the probability of a randomly chosen occupancy to be found in an isolate. The additive-constrained SARs accounts for two complimentary turn-over components of occupancies: turnover between species and turnover between sites.

AimPatterns that relate species richness with fragment area (the species–area relationship, SAR) and with isolation (the species–isolation relationship, SIR) are well documented. However, those that relate species density – the number of species within a standardized area – with fragment area (D-SAR) or isolation (D-SIR) have not been sufficiently explored, despite the potential for such an analysis to disentangle the underlying mechanisms of SARs and SIRs. Previous spatial theory predicts that a significant D-SAR or D-SIR is unlikely to emerge in taxa with high dispersal limitation, such as plants. Furthermore, a recent model predicts that the detection and the significance of D-SARs or D-SIRs may decrease with grain size. We combined a literature review with grain size-dependent sampling in a fragmented landscape to evaluate the prevalence and grain size-dependent nature of D-SARs and D-SIRs in plants.LocationWorldwide (review) and a semi-arid agro-ecosystem in Israel (case study).MethodsWe combined an extensive literature review of 31 D-SAR studies of plants in fragmented landscapes with an empirical study in which we analysed grain size-dependent D-SARs and D-SIRs using a grain size-dependent hierarchical sampling of species density and species richness in a fragmented, semi-arid agro-ecosystem.ResultsWe found that significantly increasing D-SARs are rare in plant studies. Furthermore, we found that the detection of a significant D-SAR is often possible only after the data have been stratified by species, habitat or landscape characteristics. The results from our case study indicated that the significance and the slopes of both D-SARs and D-SIRs increase as grain size decreases.Main conclusionsThese results call for a careful consideration of scale while analysing and interpreting the responses of species richness and species density to fragmentation. Our results suggest that grain size-dependent analyses of D-SARs and D-SIRs may help to disentangle the mechanisms that generate SARs and SIRs and may enable early detection of the effects of fragmentation on plant biodiversity.

Intensive agricultural activity over large areas on earth, which is necessary to meet the increasing demand of a growing human population, may lead to biodiversity loss. This loss may be mitigated by keeping natural and semi-natural patches within agricultural fields to allow the maintenance of biological diversity (‘Wildlife Friendly Agriculture’). We conducted our study in an agroecosystem comprised of small isolated patches nested within agricultural fields. We trapped reptiles in 13 sampling sites, each of which included arrays of pitfall traps in a natural patch, in the adjacent wheat field and at the patch-field edge. We conducted six trapping sessions in the spring – four times before, once immediately after and once a week after the wheat harvest. Prior to the harvest, we found an intensive movement of Trachylepis vittata, the most common reptile in our study, from the semi-natural patches into the fields, but negligible movement in the opposite direction. This pre-harvest directional movement corresponded with higher abundance of prey (i.e., arthropods) in the wheat field compared to the natural patches in early spring. The individuals that moved into the fields were adults of better body condition than those remaining in the patch, suggesting that the motivation for movement was habitat preference by individuals with high prospective fitness rather than the exclusion of subordinates. The population of T. vittata in the wheat fields and movement across habitats dropped to zero during and after the harvest. Our results provide strong evidence that the agricultural fields serve as an ecological trap to organisms inhabiting nearby natural habitats. We suggest that plans for Wildlife-Friendly Agriculture for biodiversity conservation should consider also potential negative effects, such as the ecological trap effect.

Spatial environmental heterogeneity is considered a fundamental factor for the maintenance of plant species richness. However, it still remains unclear whether heterogeneity may also facilitate coexistence at fine grain sizes or whether other processes, like mass effects and source sink dynamics due to dispersal, control species composition and diversity at these scales. In this study, we used two complimentary analyses to identify the role of heterogeneity within 15m×15m plots for the coexistence of species-rich annual communities in a semi-arid environment along a steep precipitation gradient. Specifically, we: (a) analyzed the effect of environmental heterogeneity on species, functional and phylogenetic diversity within microsites (alpha diversity, 0.06m2 and 1m2), across microsites (beta diversity), and diversity at the entire plot (gamma diversity); (b) further we used two null models to detect non-random trait and phylogenetic patterns in order to infer assembly processes, i.e. whether co-occurring species tend to share similar traits (trait convergence) or dissimilar traits (trait divergence). In general, our results showed that heterogeneity had a positive effect on community diversity. Specifically, for alpha diversity, the effect was significant for functional diversity, and not significant for either species or phylogenetic diversities. For beta diversity, all three measures of community diversity (species, functional, and phylogenetic) increased significantly, as they also did for gamma diversity, where functional measures were again stronger than for species or phylogenetic measures. In addition, the null model approach consistently detected trait convergence, indicating that species with similar traits tended to co-occur and had high abundances in a given microsite. While null model analysis across the phylogeny partly supported these trait findings, showing phylogenetic underdispersion at the 1m2 grain size, surprisingly when species abundances in microsites were analyzed they were more evenly distributed across the phylogenetic tress than expected (phylogenetic overdispersion). In conclusion, our results provide compelling support that environmental heterogeneity at a relatively fine scale is an important factor for species co-existence as it positively affects diversity as well as influences species assembly. Our study underlines the need for trait-based approaches conducted at fine grain sizes in order to better understand species coexistence and community assembly. Spatial environmental heterogeneity is considered a fundamental factor for the maintenance of plant species richness. However, it still remains unclear whether heterogeneity may also facilitate coexistence at fine grain sizes or whether other processes, like mass effects and source sink dynamics due to dispersal, control species composition and diversity at these scales. In this study, we used two complimentary analyses to identify the role of heterogeneity within 15 m × 15 m plots for the coexistence of species-rich annual communities in a semi-arid environment along a steep precipitation gradient. Specifically, we: (a) analyzed the effect of environmental heterogeneity on species, functional and phylogenetic diversity within microsites (alpha diversity, 0.06 m2 and 1 m2), across microsites (beta diversity), and diversity at the entire plot (gamma diversity); (b) further we used two null models to detect non-random trait and phylogenetic patterns in order to infer assembly processes, i.e. whether co-occurring species tend to share similar traits (trait convergence) or dissimilar traits (trait divergence). In general, our results showed that heterogeneity had a positive effect on community diversity. Specifically, for alpha diversity, the effect was significant for functional diversity, and not significant for either species or phylogenetic diversities. For beta diversity, all three measures of community diversity (species, functional, and phylogenetic) increased significantly, as they also did for gamma diversity, where functional measures were again stronger than for species or phylogenetic measures. In addition, the null model approach consistently detected trait convergence, indicating that species with similar traits tended to co-occur and had high abundances in a given microsite. While null model analysis across the phylogeny partly supported these trait findings, showing phylogenetic underdispersion at the 1m2 grain size, surprisingly when species abundances in microsites were analyzed they were more evenly distributed across the phylogenetic tress than expected (phylogenetic overdispersion). In conclusion, our results provide compelling support that environmental heterogeneity at a relatively fine scale is an important factor for species co-existence as it positively affects diversity as well as influences species assembly. Our study underlines the need for trait-based approaches conducted at fine grain sizes in order to better understand species coexistence and community assembly.

Intraspecific trait variability plays an important role in species adaptation to climate change. However, it still remains unclear how plants in semi-arid environments respond to increasing aridity. We investigated the intraspecific trait variability of two common Mediterranean annuals (Geropogon hybridus and Crupina crupinastrum) with similar habitat preferences. They were studied along a steep precipitation gradient in Israel similar to the maximum predicted precipitation changes in the eastern Mediterranean basin (i.e. −30% until 2100). We expected a shift from competitive ability to stress tolerance with decreasing precipitation and tested this expectation by measuring key functional traits (canopy and seed release height, specific leaf area, N- and P-leaf content, seed mass). Further, we evaluated generative bet-hedging strategies by different seed traits. Both species showed different responses along the precipitation gradient. C. crupinastrum exhibited only decreased plant height towards aridity, while G. hybridus showed strong trends of generative adaptation to aridity. Different seed trait indices suggest increased bet-hedging of G. hybridus in arid environments. However, no clear trends along the precipitation gradient were observed in leaf traits (specific leaf area and leaf N-/P-content) in both species. Moreover, variance decomposition revealed that most of the observed trait variation (≫50 is found within populations. The findings of our study suggest that responses to increased aridity are highly species-specific and local environmental factors may have a stronger effect on intraspecific trait variation than shifts in annual precipitation. We therefore argue that trait-based analyses should focus on precipitation gradients that are comparable to predicted precipitation changes and compare precipitation effects to effects of local environmental factors. Intraspecific trait variability plays an important role in species adaptation to climate change. However, it still remains unclear how plants in semi-arid environments respond to increasing aridity. We investigated the intraspecific trait variability of two common Mediterranean annuals (Geropogon hybridus and Crupina crupinastrum) with similar habitat preferences. They were studied along a steep precipitation gradient in Israel similar to the maximum predicted precipitation changes in the eastern Mediterranean basin (i.e. −30% until 2100). We expected a shift from competitive ability to stress tolerance with decreasing precipitation and tested this expectation by measuring key functional traits (canopy and seed release height, specific leaf area, N- and P-leaf content, seed mass). Further, we evaluated generative bet-hedging strategies by different seed traits. Both species showed different responses along the precipitation gradient. C. crupinastrum exhibited only decreased plant height towards aridity, while G. hybridus showed strong trends of generative adaptation to aridity. Different seed trait indices suggest increased bet-hedging of G. hybridus in arid environments. However, no clear trends along the precipitation gradient were observed in leaf traits (specific leaf area and leaf N-/P-content) in both species. Moreover, variance decomposition revealed that most of the observed trait variation (≫50%) is found within populations. The findings of our study suggest that responses to increased aridity are highly species-specific and local environmental factors may have a stronger effect on intraspecific trait variation than shifts in annual precipitation. We therefore argue that trait-based analyses should focus on precipitation gradients that are comparable to predicted precipitation changes and compare precipitation effects to effects of local environmental factors.

Dominance relationships among species play a major role in the structure of animal communities. Yet, dominant species with different trade-offs in resource exploitation and monopolization could affect community structure in variable ways. In ants, dominant species could be classified into either behavioral dominants that exhibit territorial aggression or numerical dominants that exhibit high biomass or frequency of occurrence. While each class of dominance has generally been found to negatively affect the foraging activity of species in ant communities, the concurrent effect of both classes of species has never been tested. Here, we examined the effects of two behaviorally dominant species, Crematogaster inermis and Monomorium salomonis, and a numerically dominant species, Messor arenarius, on the foraging behavior of seed-eating species in a desert ant assemblage. In a 1-year study, the foraging activity of the ant species was assessed using seed baits, which were sampled during night and day. While the numerically dominant species exhibited high foraging efficiency and negatively affected the ability of other seed-eating species to obtain seeds, significantly more seeds remained at baits that were occupied the previous night by each of the two behaviorally dominant species, possibly due to aggressive exclusion of M. arenarius foragers from the baits. This exclusion also facilitated greater foraging activity of the seed-eating species. Our results demonstrate how these two types of dominance could differently affect the foraging activity of ant species in the community.

Habitat loss reduces species diversity, but the effect of habitat fragmentation on number of species is less clear because fragmentation generally accompanies loss of habitat. We compared four methods that aim to decouple the effects of fragmentation from the effects of habitat loss. Two methods are based on species-area relations, one on Fisher's alpha index of diversity, and one on plots of cumulative number of species detected against cumulative area sampled. We used these methods to analyze the species diversity of spiders in 2, 3.2 × 4 km agricultural landscapes in Southern Judea Lowlands, Israel. Spider diversity increased as fragmentation increased with all four methods, probably not because of the additive within-patch processes, such as edge effect and heterogeneity. The positive relation between fragmentation and species diversity might reflect that most species can disperse through the fields during the wheat-growing season. We suggest that if a given area was designated for the conservation of spiders in Southern Judea Lowlands, Israel, a set of several small patches may maximize species diversity over time. Resumen: La perdida de habitat reduce la diversidad de especies, pero el efecto de la fragmentacion del habitat sobre muchas especies es menos claro porque la fragmentacion generalmente es acompanada por la perdida de habitat. Comparamos cuatro metodos que tratan de separar los efectos de la fragmentacion sobre los efectos de la perdida de habitat. Dos metodos se basan en las relaciones especies-area, uno en el indice de diversidad alfa de Fisher, y uno en graficos del numero acumulativo de especies detectadas versus el area muestreada acumulada. Utilizamos estos metodos para analizar la diversidad de aranas en 2 paisajes agricolas de 3.2 × 4 km en las Tierras Bajas de Judea del Sur, Israel. La diversidad de aranas incremento a medida que incremento la fragmentacion con los cuatro metodos, probablemente no debido a los procesos aditivos intra-parche, como el efecto de borde y la heterogeneidad. La relacion positiva entre la fragmentacion y la diversidad de especies puede ser reflejo de que la mayoria de las especies se pueden dispersar en los campos durante la epoca de siembra de trigo. Sugerimos que si un area determinada fuera designada para la conservacion de aranas en las Tierras Bajas de Judea del Sur, Israel, un conjunto de parches muy pequenos puede maximizar la diversidad de especies en el tiempo.

Aims: (1) Understanding how the relationship between species richness and its determinants depends on the interaction between scales at which the response and explanatory variables are measured. (2) Quantifying the relative contributions of local, intermediate and large-scale determinants of species richness in a fragmented agro-ecosystem. (3) Testing the hypothesis that the relative contribution of these determinants varies with the grain size at which species richness is measured. Location: A fragmented agro-ecosystem in the Southern Judea Lowland, Israel, within a desert–Mediterranean transition zone. Methods: Plant species richness was estimated using hierarchical nested sampling in 81 plots, positioned in 38 natural vegetation patches within an agricultural matrix (mainly wheat fields) among three land units along a sharp precipitation gradient. Explanatory variables included position along that gradient, patch area, patch isolation, habitat heterogeneity and overall plant density. We used general linear models and hierarchical partitioning of variance to test and quantify the effect of each explanatory variable on species richness at four grain sizes (0.0625, 1, 25 and 225 m2). Results: Species richness was mainly affected by position along a precipitation gradient and overall plant density, and to a lesser extent by habitat heterogeneity. It was also significantly affected by patch area and patch isolation, but only for small grain sizes. The contribution of each explanatory variable to explained variance in species richness varied with grain size, i.e. scale-dependent. The influence of geographic position and habitat heterogeneity on species richness increased with grain size, while the influence of plant density decreased with grain size. Main conclusions: Species richness is determined by the combined effect of several scale-dependent determinants. Ability to detect an effect and effect size of each determinant varies with the scale (grain size) at which it is measured. The combination of a multi-factorial approach and multi-scale sampling reveals that conclusions drawn from studies that ignore these dimensions are restricted and potentially misleading.

To test the effects of connectivity on fish diversity in isolated reef patches we deployed pairs of artificial reefs (AR) at constant distances (12 and 25 m) from a large continuous reef and added series of small ARs to half of them. These small reefs served as stepping-stones to increase fish movement between the large ARs and the continuous reef. Species gain and loss curves were compared to obtain deeper understanding of the underlying mechanisms in relation to the theory of island biogeography. We found that AR without stepping-stones maintained up to 57-fold more individuals than ARs with stepping-stones during mass recruitment events that were dominated by the family Apogonidae. However, in-between these mass recruitment events the overall impact of the stepping-stones on richness and abundance was small. By contrast, increasing distance from the continuous reef from 12 to 25 m increased fish richness, although this was confounded with time since AR deployment. Increase in richness with distance was predominantly caused by elevated species gain. Our results suggest that fish assemblages respond in distinct ways to two types of isolation: (1) Increased richness with distance from a continuous reef, and (2) increased fluctuation in abundance with decreased connectivity. The latter may be the outcome of accumulation and then abrupt emigrations of fishes from isolated reefs. This study confirms that the spatial setting of reef patches in relation to larger or continuous reefs alters fish assemblages, which may be important for planning AR deployments that maximizes diversity.

We studied the distribution of arthropods in the Arava desert on both sides of the Israeli-Jordanian border, to assess the impact of different anthropogenic pressures on the local fauna. We examined how different landscape units, proximity to agricultural fields, and human societies, might affect the diversity of ground dwelling beetles, and spiders, using ordination and diversity estimation methods. Our results suggest that although both countries contain similar habitats, each has its own unique characteristics, probably due to different cultural practices. The immediate repercussion is that loss of a habitat on one side of the border cannot be compensated with preservation of the same habitat across the border, due to fauna dissimilarity. For example, beetle species can be assembled according to landscape units, but within each landscape unit they show dissimilarities that are based on the geopolitical location. Spiders fail to assemble according to landscape units but cluster as a unique group within Israel. Both landscape unit type and the border, were found to be important for the overall species diversity of this ecosystem and therefore “redundancy” should be carefully applied, especially across geopolitical borders.

Fish abundance is often better predicted by microhabitat variables on continuous reefs than on isolated patch reefs. Although this was suggested to stem from reduced post-recruitment relocation, this has not been shown experimentally. We found the relationship between the presence of a coral-dwelling fish, Dascyllus marginatus, and the size of its coral host to differ between corals on continuous reefs and the sparsely distributed corals on sandy bottoms. Empty transplanted corals were colonized exclusively by new recruits when on the sandy bottom, and both by new recruits and post-recruitment dispersal of adults when on the continuous reef. New recruits settled predominantly into small corals, although analyses of recruitment patterns were confounded by low recruitment in the studied years. Both tank experiments and field survey data suggest that the presence of recruits in small corals is at least partially driven by predation by the dottyback, Pseudochromis olivaceus, which lives predominantly in large corals within both habitats. Consequently, we suggest that the relationship between fish presence and coral size differs between the habitats due to coral size dependent predation on recruits and variability in the importance of direct recruitment to replenish fish populations.

Many agricultural greenhouse crops suffer reduced yields due to insufficient pollination. This problem can be alleviated by introducing efficient pollinating insects into the greenhouse. The bee Xylocopa puhescens Spinola 1838, a candidate for domestication as an agricultural pollinator, is unique in its facultative social organization. Females either nest solitarily, or together with a second female (a non-reproducing guard). Social nesting occurs when food and nest sites are limited, and carries fitness benefits and costs to the bees as.compared to solitary nesting. The implications of X pubescens' social organization for crop pollination were investigated. Honeydew melons were grown as a model crop in a small greenhouse. The non-crop plants Portulaca oleracea L, Solanum rantonnetii C. Lavandula angustifolia Mill and Ocimum basilicum L supplemented the bees' diet. Social and solitary X pubescens nesters were introduced into the greenhouse in alternation. The bees' daily activity pattern, the frequency and duration of visits to each flower species, and the run-lengths of consecutive visits to each flower species were recorded. The melons' fruit set, and the fruits' mass and seed number, were determined. Social nesters visited P oleracea more frequently than solitary bees when this species was in bloom. After P oleracea finished blooming, socially nesting bees visited melon more often than solitary nesters Social bees spent a longer time at the melon patch and tended to be more flower constant than solitary nesters, but spent less time per flower than solitary individuals. Solitary and social bees did not differ in their daily activity patterns and flower visitation rates. Pollination by both types of nesters resulted in similar fruit sets, fruit mass and fruit seed numbers. The dissimilarities in foraging behaviour may reflect differences in the dietary demands of solitary vs social nesters. The similarity in fruit sets and flower constancy suggests that both nest types provide pollination services of similar quality.

Understanding species-diversity patterns in heterogeneous landscapes invites comprehensive research on how scale-dependent processes interact across scales. We used two common beetle families (Tenebrionidae, detrivores; Carabidae, predators) to conduct such a study in the heterogeneous semi-arid landscape of the Southern Judean Lowland (SJL) of Israel, currently undergoing intensive fragmentation. Beetles were censused in 25 different-sized patches (500–40,000 m2). We used Fisher’s α and non-parametric extrapolators to estimate species diversity from 11,125 individuals belonging to 56 species. Patch characteristics (plant species diversity and cover, soil cover and degree of stoniness) were measured by field transects. Spatial variables (patch size, shape, physiognomy and connectivity) and landscape characteristics were analyzed by GIS and remote-sensing applications. Both patch-scale and landscape-scale variables affected beetle species diversity. Path-analysis models showed that landscape-scale variables had the strongest effect on carabid diversity in all patches. The tenebrionids responded differently: both patch-scale and landscape-scale variables affected species diversity in small patches, while mainly patch-scale variables affected species diversity in large patches. Most of the paths affected species diversity both directly and indirectly, combining the effects of both patch-scale and landscape-scale variables. These results match the biology of the two beetle families: Tenebrionidae, the less mobile and more site-attached family, responded to the environment in a fine-grained manner, while the highly dispersed Carabidae responded to the environment in a coarse-grained manner. We suggest that understanding abiotic and biotic variable interactions across scales has important consequences for our knowledge of community structure and species diversity patterns at large spatial scales.

The increase in species richness with area is known as the species–area relationship (SPAR). Although several mutually non-exclusive processes may produce the SPAR, the null, often ignored, hypothesis states that a SPAR can be generated by random placement alone. The log–log-transformed SPAR of coral reef fishes on small patch-reefs revealed a steep slope of 0.55. However, this slope was dependent on the cumulative area of the reef examined and was therefore affected by random placement. After statistically removing the contribution of random placement from the SPAR, the slope was estimated to be 0.21. This is consistent with estimates from other, mostly terrestrial, systems. Furthermore, a randomization procedure, where the probability of fishes to reach a patch was proportional to reef area, showed that the field measured SPAR did not differ from random placement. In addition, fish assemblages on species poor reefs did not form subsets of species rich reefs (i.e., no nestedness) beyond that expected from random placement. Steep log–log-transformed SPARs can be formed by random placement alone, indicating that caution should be used when assigning an ecological meaning to SPARs generated from small spatial scales.

The peace treaty between Israel and Jordan found the Arava desert ecosystem, shared by the two countries, in a state of developmental dichotomy. On the Israeli side, vast lands have been settled and transformed into agricultural fields, while the Jordanian side has remained relatively intact and inhabited by only a few traditional and pastoral societies. This study examined the effect of different landscape units and proximity to agriculture on reptile diversity and rodent community structure on both sides of the border. It appears that in addition to the effect of proximity to agricultural fields and landscape habitat, the border between the two countries may play a role in determining diversity on the respective sides. While reptile abundance was generally higher on the Israeli side of the border, diversity was found to be significantly higher on the Jordanian side. Rodent community structure also revealed significant differences between the two sides of the border, mainly due to the more favorable conditions for psammophilic gerbils in Jordan. When comparing Western society with pastoral traditional society, it appears that development activities of the former have altered diversity and community structure of the taxa studied in the Arava. We suggest that in addition to the effects of habitats and human disturbances, such as modern agricultural practices, cultural differences between societies should be considered when conservation plans are developed for cross-border ecosystems.

Summary 1. We tested the hypothesis that Gerbillus henleyi (de Winton 1903), the smallest species (10 g) of a pssamophilic guild in Israel, is scarce on relatively productive dunes of the Israeli desert, due to negative interactions from the common G. allenby i (Thomas 1918) and G. pyramidum (Geoffroy 1825). 2. The alternative hypothesis was that scarcity on sand resulted from the size of its naked hind feet, that do not allow efficient locomotion on sand. 3. Despite their naked soles the weight-bearing surface of G. henleyi feet carry less mass/area than those of any other species. 4. We measured interaction coefficients with the two common species using fieldmanipulation experiments in two enclosures. 5. Habitat usage of G. henleyi changed from significantly preferring the stabilized sand, when alone, to significantly using the semistabilized dune, when G. allenbyi was also present. 6. We also estimated the interaction coefficients and calculated the G. henleyi ’s isoclines competing with the two common gerbil species using a technique we developed elsewhere. 7. The stability analysis of the isoclines of G. henleyi competing with either G. allenbyi or with G. pyramidum suggests that stable coexistence occurs when G. henleyi is relatively scarce while the competitors are common. 8. Interspecific competition from either G. allenbyi or G. pyramidum accounts for 90·3% reduction in G. henleyi density, relative to when it is alone. 9. We concluded that the negative interactions from congeners was the major cause for the scarcity of G. henleyi on the relatively rich sand dunes of the Israeli desert.

We studied the large-scale spatialÐtemporal distribution pattern of the Mediterranean fruit sy, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) to understand whether long-term dispersal may affect its maintenance in a highly patchy and isolated arid environment. The study area contained few dispersed settlements and agricultural plots covering 3,000 km 2 , ranging from 100 to 900 m in altitude in southern Israel. Due to the arid nature of the study area, no wild hosts existed outside the settlements. Data were collected from three settlements at different altitudes from 1999 to 2002. During 2000, adult sies were monitored throughout the entire area. Data were incorporated into a geographic information system, and weekly spatial distribution charts were produced and analyzed. Our results suggest that, within the study area, C. capitata overwinters in sites 400 mi n altitude with abundant winter hosts but not at higher altitudes. In remote settlements and agricultural areas at higher altitudes, sies reappeared every year in midsummer, which can only be explained by annual migration from the lower altitudes. Our results demonstrate that sies migrate at least 50 km, probably over a single generation, before reaching some of the remote havens within the study area. This long-distance migration has far-reaching consequences for maintenance of remote populations and should be taken into consideration for future basic research and applied control practices of C. capitata.

A positive correlation is often found between fish species diversity on coral reefs and their degree of isolation. We examined whether isolation creates differences in fish assemblages among reefs through changes in predation pressure. First, small artificial reefs were placed at increasing distances from a naturally continuous reef, over a sloping bottom. Species richness and density of each species increased with isolation. Next, artificial reefs were relocated, together with all their fish inhabitants, closer to the natural reef. Following relocation, resident fishes of the artificial reefs exhibited a sharp decline in numbers, while predatory fish density increased. Both video obser- vations of the relocated artificial reefs and the correlation between piscivore aggregation and decline of the resident fishes revealed that the cause of decline was the strong predation around the artificial reefs. The decline was density-dependent, such that the per-capita rate of decline was higher on arti- ficial reefs with higher fish density. This study shows that the impact of piscivores on resident fish is modified by small-scale isolation. The results suggest that the high density of fish on small, isolated reefs is enabled by low predation.

The geographical distribution of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is limited to relatively warm regions and does not cross the 41° north latitude. A recent study has demonstrated that, in contrast to the earlier suggested hypothesis, that Mediterranean fruit fly can survive the winter in relatively cold areas, it does not overwinter in such areas but reinvades them annually from adjacent warmer sites. In the present work, we use a large-scale spatial approach to describe the spatiotemporal dynamics of Mediterranean fruit fly in a large heterogeneous landscape as well as discuss the consequences of such dynamics for basic research and control practices. During a 2-yr period (2000–2001), over the central part of Israel (6,875 km2), adult males were monitored and recorded weekly by using Steiner-like traps. Data obtained were incorporated into a geographic information system to produce weekly distribution maps of C. capitata within the study area. The patterns of change in population sizes through time were consistent in both years, suggesting that C. capitata overwinters along the coastal plain and the Jordan Valley. Reinvasion to the higher altitudes is followed by a population increase in the warmer, lower altitudes, during the spring and early summer. By midsummer, flies were found at all sites within the study area. However, flies started disappearing from the high-altitude areas during fall and were absent from these areas during winter. We suggest that understanding such spatiotemporal dynamics has far-reaching consequences for future basic research as well as control and eradication programs.

Contrary to the past belief that the species richness-productivity relationship (SRPR) is characterized by a single “true” pattern, several analyses have shown that a heterogeneous distribution of SRPRs exists and that the patterns' distribution of a SRPR is sensitive to the directness of the estimates of productivity. A simple conceptual model demonstrates that taking into account underlying relationships connecting productivity with species richness produces a heterogeneous distribution of relationships. We suggest that the search for a single pattern for SRPR has reached a dead end, and that we should direct our research focus to exploring the mechanisms responsible for the various SRPRs.

We studied the effect of a dominant species, Gerbillus pyramidum (Egyptian sand gerbil), on the patch use of its subordinate competitor, G. andersoni allenbyi (Allenby's gerbil), to better understand interspecific competition between the two species. We used manipulated resource patches (seed trays) covered with cages with two adjustable species-specific gates (either opened or closed to the bigger-dominant species, but always opened to the subordinate one). We recorded species tracks around and on the seed trays and giving-up densities (GUDs) of seeds in the trays after each night of foraging. G. a. allenbyi depleted seed patches to a lower level whenever G. pyramidum was given the opportunity to forage on the seed trays (i.e., present on the grid). This result held regardless of whether G. pyramidum was actually present at a particular station. We suggest that competition from G. pyramidum occurs both directly by interference, in which G. a. allenbyi is forced to be active in the late part of the night, and indirectly by exploitation via resource depletion by G. pyramidum in the early part of the night. The results suggest that interspecific competition from G. pyramidum reduces seed availability and the richness of the environment for G. a. allenbyi enough to affect the marginal value of energy for G. a. allenbyi individuals and cause them to experience lower costs of predation and manifest lower GUDs.