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  • 1
    Language: Spanish
    In: Conservation Biology, February 2012, Vol.26(1), pp.150-159
    Description: :  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.
    Keywords: Arthropods ; Landscape ; Sloss ; Species Diversity ; Species‐Area Relation ; Artrópodos ; Diversidad De Especies ; Paisaje ; Relación Especies‐Área ; Sloss
    ISSN: 0888-8892
    E-ISSN: 1523-1739
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  • 2
    In: Journal of Biogeography, April 2017, Vol.44(4), pp.937-949
    Description: Byline: Yoni Gavish, Yaron Ziv Keywords: biodiversity patterns; islands; Jaccard; landscape; macroecology; multiple-sites similarity; occupancy-frequency distribution; patches; Sorensen; spatial ecology Abstract 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. Article Note: Editor: Francois Guilhaumon CAPTION(S): Appendix S1 AICc, wAICc and expected AICc. Appendix S2 References and information on data sets. Appendix S3 Linear regressions of wAICc.
    Keywords: Biodiversity Patterns ; Islands ; Jaccard ; Landscape ; Macroecology ; Multiple‐Sites Similarity ; Occupancy‐Frequency Distribution ; Patches ; Sørensen ; Spatial Ecology
    ISSN: 0305-0270
    E-ISSN: 1365-2699
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  • 3
    In: PLoS ONE, 2016, Vol.11(12)
    Description: Understanding the main processes that affect community similarity have been the focus of much ecological research. However, the relative effects of environmental and spatial aspects in structuring ecological communities is still unresolved and is probably scale-dependent. Here, we examine the effect of habitat identity and spatial distance on fine-grained community similarity within a biogeographic transition zone. We compared four hypotheses: i) habitat identity alone, ii) spatial proximity alone, iii) non-interactive effects of both habitat identity and spatial proximity, and iv) interactive effect of habitat identity and spatial proximity. We explored these hypotheses for spiders in three fragmented landscapes located along the sharp climatic gradient of Southern Judea Lowlands (SJL), Israel. We sampled 14,854 spiders (from 199 species or morphospecies) in 644 samples, taken in 35 patches and stratified to nine different habitats. We calculated the Bray-Curtis similarity between all samples-pairs. We divided the pairwise values to four functional distance categories (same patch, different patches from the same landscape, adjacent landscapes and distant landscapes) and two habitat categories (same or different habitats) and compared them using non-parametric MANOVA. A significant interaction between habitat identity and spatial distance was found, such that the difference in mean similarity between same-habitat pairs and different-habitat pairs decreases with spatial distance. Additionally, community similarity decayed with spatial distance. Furthermore, at all distances, same-habitat pairs had higher similarity than different-habitats pairs. Our results support the fourth hypothesis of interactive effect of habitat identity and spatial proximity. We suggest that the environmental complexity of habitats or increased habitat specificity of species near the edge of their distribution range may explain this pattern. Thus, in transitions zones care should be taken when using habitats as surrogate of community composition in conservation planning since similar habitats in different locations are more likely to support different communities.
    Keywords: Research Article ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Earth Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: Oecologia, 2016, Vol.180(1), pp.231-242
    Description: Grazing plays an important role in shaping ecological communities in human-related ecosystems. Although myriad studies have explored the joint effect of grazing and climate on plant communities, this interactive effect has rarely been studied in animals. We hypothesized that the effect of grazing on the reptile community varies along a climatic gradient in relation to the effect of grazing on habitat characteristics, and that grazing differentially affects reptiles of different biogeographic regions. We tested our hypotheses by collecting data on environmental characteristics and by trapping reptiles in four heterogeneous landscapes experiencing differing grazing intensities and distributed along a sharp climatic gradient. We found that while reptile diversity increased with grazing intensity at the mesic end of the gradient, it decreased with grazing intensity at the arid end. Moreover, the proportion of reptile species of differing biogeographic origins varied with the interactive effect of climate and grazing. The representation of species originating in arid biogeographic zones was highest at the arid end of the climatic gradient, and representation increased with grazing intensity within this area. Regardless of the climatic context, increased grazing pressure results in a reduction in vegetation cover and thus in changes in habitat characteristics. By reducing vegetation cover, grazing increased habitat heterogeneity in the dense mesic sites and decreased habitat heterogeneity in the arid sites. Thus, our results suggest that the same direction of habitat alteration caused by grazing may have opposite effects on biodiversity and community composition in different climatic contexts.
    Keywords: Arid ; Biogeography ; Ecotone ; Fisher’s alpha ; Habitat heterogeneity ; Herpetofauna ; Mediterranean
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 5
    Language: English
    In: Biodiversity and Conservation, 2019, Vol.28(3), pp.769-786
    Description: 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.
    Keywords: Agroecosystems ; Araneae ; Community composition ; Effective diversity ; Fragmentation ; Meta-community ; Scale
    ISSN: 0960-3115
    E-ISSN: 1572-9710
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  • 6
    In: Methods in Ecology and Evolution, November 2018, Vol.9(11), pp.2273-2284
    Description: The area of occupancy (AOO) is a widely used index in conservation assessments, notably in criteria B2 of the International Union for Conservation of Nature (IUCN) red‐list. However, IUCN guidelines require assessing AOO at finer resolution than is generally available. For this reason, extrapolation techniques have been proposed to predict finer AOO from coarser resolution data. Here, we apply 10 published downscaling models to the distributions of a large number of plant and bird species' in contrasting landscapes. We further compare the output of two ensemble models, one relying on all 10 downscaling models and one a subset of five models that can be fit rapidly and robustly, with minimal oversight required. We further compare the accuracy of downscaled predictions with respect to species prevalence. Across all landscapes and taxa, the models predicted AOO consistently. Some, such as the power law and Hui models, were nonlinear with respect to species prevalence. Some models consistently over or under predicted, such as the Nachman and Poisson models. Furthermore, some models proved to give more variable predictions than other models, e.g. Nachman and power law. For these reasons, none of these models are suitable for downscaling if used individually. The Thomas model was also rejected, because it is too computationally intensive, even though its predictions are relatively unbiased. The most effective model, when used by itself, was the improved binomial model. However, the two ensemble models were able to provide accurate predictions of AOO with low variability compared to using any one single model. There was no significant loss in performance using the simpler ensemble model, and therefore this solution is the least computationally intensive and requires least user oversight. Our results show that downscaling models could be potential tools to reliably estimate AOO for conservation assessments. Under circumstances where there is no a priori reason to prefer one model over another then an ensemble of these models may be the best solution for batch analysis of IUCN status under criteria B2. Moreover, we foresee the use of downscaling for the production of other biodiversity indicators, such as for invasive species monitoring. La zone d'occupation (AOO) est un indice largement utilisé dans les évaluations de conservation, notamment pour le critère B2 de la liste rouge de l'Union internationale pour la conservation de la nature (UICN). Cependant, les directives de l'UICN exigent une évaluation de l'AOO à une résolution plus fine que celle qui est généralement disponible. Pour cette raison, des techniques d'extrapolation ont été proposées pour prédire les AOO plus finement à partir de données de résolution plus grossières. Ici, nous appliquons 10 modèles publiés de réduction d'échelle à la distribution d'un grand nombre d'espèces de plantes et d'oiseaux dans des paysages contrastés. Nous comparons ensuite les résultats de deux modèles d'ensemble, l'un reposant sur les 10 modèles de réduction d'échelle et l'autre sur un sous‐ensemble de 5 modèles pouvant s'adapter rapidement et de manière robuste, et nécessitant un minimum d'inspection. Nous comparons ensuite la précision des prévisions à échelle réduite en ce qui concerne l'incidence des espèces. Pour tous les paysages et les taxons, les modèles ont prédit l'AOO de manière cohérente. Certains, tels que la loi de puissance et les modèles Hui, étaient non linéaires en ce qui concerne la prévalence des espèces. Certains modèles ont constamment sur‐ ou sous‐prédit, tels que les modèles Nachman et Poisson. En outre, quelques modèles ont donné des prédictions plus variables que d'autres, par exemple Nachman et la loi de puissance. Pour ces raisons, aucun de ces modèles ne convient à la réduction d'échelle s'il est utilisé individuellement. Le modèle de Thomas a également été rejeté, car il est trop intensif en calcul, même si ses prédictions sont relativement non biaisées. Le modèle le plus efficace, lorsqu'il était utilisé seul, fut le modèle binomial amélioré. Cependant, les deux modèles d'ensemble ont été en mesure de fournir des prédictions précises de l'AOO avec une faible variabilité par rapport à l'utilisation d'un seul modèle unique. Il n'y a pas eu de perte significative de performance en utilisant le modèle d'ensemble plus simple. Par conséquent, cette solution est la moins gourmande en calculs et nécessite moins de supervision de la part de l'utilisateur. Nos résultats montrent que les modèles de réduction d'échelle pourraient être des outils potentiels pour estimer de manière fiable les AOO pour les évaluations de conservation. Dans des circonstances ù il n'y a aucune raison a priori de préférer un modèle à un autre, un ensemble de ces modèles peut être la meilleure solution pour l'analyse par lots du statut UICN selon le critère B2. En outre, nous prévoyons l'utilisation de la réduction d'échelle pour la production d'autres indicateurs de la biodiversité, tels que le suivi des espèces invasives. Het verspreidingsgebied (area of occupancy, AOO) is een veelgebruikte index bij vaststellingen voor natuurbehoud, onder meer in criterium B2 van de rode lijst van de International Union for Conservation of Nature (IUCN). IUCN richtlijnen vereisen echter dat het AOO vastgesteld wordt op een fijnere resolutie dan algemeen beschikbaar is. Daarom werden er extrapolatietechnieken voorgesteld om fijner het AOO te voorspellen uit data met grovere resolutie. Hier passen we 10 gepubliceerde schaalverkleiningsmodellen toe op de distributies van een groot aantal plant‐ en vogelsoorten in contrasterende landschappen. Verder vergelijken we nog de output van twee ensemble modellen, één afhankelijk van alle 10 schaalverkleiningsmodellen en één van een subset van 5 modellen die op snelle en robuuste wijze gefit kunnen worden met zo min mogelijk toezicht vereist. Verder vergelijken we de nauwkeurigheid van in schaal verkleinde voorspellingen ten aanzien van het algemeen voorkomen van soorten. Over alle modellen en taxa heen voorspelden de modellen het AOO op consistente wijze. Sommigen, zoals de power law en Hui modellen, waren niet‐lineair ten aanzien van het voorkomen van soorten. Sommige modellen waren consistent in over‐ of onderschattingen, zoals de Nachtmann en Poisson modellen. Verder bleken sommige modellen variabelere voorspellingen te geven dan anderen, e.g. Nachtmann en power law. Omwille van deze redenen zijn geen van deze modellen geschikt voor schaalverkleining als ze individueel gebruikt worden. Het Thomas model werd ook afgewezen omdat het computationeel te intensief is, ook al zijn de voorspellingen relatief onbevooroordeeld. Het op zich meest effectieve model was het verbeterde binomiale model. De twee ensemble modellen waren echter in staat om nauwkeurige voorspellingen van het AOO te voorzien, met lage variabiliteit vergeleken met het gebruik van één enkel model. Er was geen significant verlies aan performantie bij gebruik van het simpelere ensemble model en dus is deze oplossing de minst computationeel intensieve met het minste toezicht door de gebruiker vereist. Onze resultaten tonen dat schaalverkleiningsmodellen potentiële hulpmiddelen kunnen zijn om betrouwbare schattingen te maken van het AOO in het kader van natuurbehoud. In omstandigheden waar er geen a priori reden is om één model boven een ander te verkiezen zou een ensemble van deze modellen de beste oplossing kunnen zijn voor batch analyse van IUCN status onder criterium B2. Bovendien verwachten we gebruik bij schaalverkleining voor de productie van andere biodiversiteitsindicatoren, zoals monitoren van invasieve soorten.
    Keywords: Area Of Occupancy ; Atlas ; Conservation Assessment ; Red Listing ; Scale
    ISSN: 2041-210X
    E-ISSN: 2041-210X
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