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  • Ecology
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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
    Language: English
    In: Oecologia, 2016, Vol.180(1), pp.243-244
    Keywords: Livestock ; Reptiles ; Agroecosystems;
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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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
    In: Canadian Journal of Zoology, 2017, Vol.96(5), pp.466-472
    Description: The extinction of a single species from a local community may carry little cost in terms of species diversity, yet its loss eliminates its biotic and abiotic interactions. We describe such a scenario in the Arava desert, where different cultural and law enforcement practices exclude Dorcas gazelles ( Gazella dorcas (Linnaeus, 1758)) from the Jordanian side of the border while protecting their populations on the Israeli side. We found that gazelles break the soil crust, formed in desert systems after annual flooding, thereby creating patches of loose and cooler sand that are used by pit-building antlions (Neuroptera: Myrmeleontidae). When we artificially broke the soil crust on both sides of the border, we found a significant increase in antlion density in these patches, but only on the Israeli side. On the Jordanian side, where no gazelles have been observed since the early 1980s, no antlions colonized either control or manipulated plots. Additional choice/no-choice feeding experiments, in which we offered antlions to lizards and birds, revealed that the effect of humans on gazelles cascades farther, as antlions serve as a palatable food source for both groups. Thus, the human-mediated loss of nontrophic interactions between gazelles and antlions cascades to the loss of trophic interactions between antlions and their predators.
    Description: Si la disparition d’une seule espèce dans une communauté locale n’est pas nécessairement très coûteuse sur le plan la diversité spécifique, la perte de cette espèce élimine toutefois ses interactions biotiques et abiotiques. Nous décrivons un tel scénario dans le désert d’Arava, où des pratiques culturelles et d’application de la loi divergentes excluent les gazelles dorcas ( Gazella dorcas (Linnaeus, 1758)) du côté jordanien de la frontière, mais en protègent les populations du côté israélien. Nous avons constaté que les gazelles brisent la croûte du sol, formée dans des systèmes désertiques après les crues annuelles, créant ainsi des parcelles de sable plus meuble et frais utilisées par des fourmilions (neuroptères : myrméléontidés) fouisseurs. Après avoir brisé artificiellement la croûte du sol des deux côtés de la frontière, nous avons noté une augmentation significative de la densité de fourmilions dans ces parcelles, mais seulement du côté israélien. Du côté jordanien, où aucune gazelle n’a été observée depuis le début des années 1980, aucun fourmilion n’a colonisé les parcelles témoins ni les parcelles manipulées. D’autres expériences d’alimentation dans lesquelles des fourmilions étaient offerts à des lézards et des oiseaux ont révélé que l’effet des humains sur les gazelles se propage en cascade, puisque les fourmilions servent de source de nourriture attrayante pour les deux groupes. Ainsi, la disparition médiée par les humains d’interactions non trophiques entre les gazelles et les fourmilions se propage en cascade pour mener à la disparition d’interactions trophiques des fourmilions avec leurs prédateurs. [Traduit par la Rédaction]
    Keywords: Ecological Engineer ; Food Web ; Dorcas Gazelle ; Gazella Dorcas ; Antlion ; Neuroptera ; Myrmeleontidae ; Desert ; Ingénieur Écologique ; Réseau Trophique ; Gazelle Dorcas ; Gazella Dorcas ; Fourmilion ; Neuroptères ; Myrméléontidés ; Désert
    ISSN: 0008-4301
    E-ISSN: 1480-3283
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  • 6
    Language: English
    In: Oecologia, August 2017, Vol.184(4), pp.859-871
    Description: Elucidating the factors determining reproductive success has challenged scientists since Darwin, but the exact pathways that shape the evolution of life history traits by connecting extrinsic (e.g., landscape structure) and intrinsic (e.g., female's age and endosymbionts) factors and reproductive success have rarely been studied. Here we collected female fleas from wild rodents in plots differing in their densities and proportions of the most dominant rodent species. We then combined path analysis and model selection approaches to explore the network of effects, ranging from micro to macroscales, determining the reproductive success of these fleas. Our results suggest that female reproductive success is directly and positively associated with their infection by Mycoplasma bacteria and their own body mass, and with the rodent species size and total density. In addition, we found evidence for indirect effects of rodent sex and rodent community diversity on female reproductive success. These results highlight the importance of exploring interrelated factors across organization scales while studying the reproductive success of wild organisms, and they have implications for the control of vector-borne diseases.
    Keywords: Fitness ; Life History ; Model Selection ; Parasites ; Path Analysis ; Scales ; Arthropod Vectors ; Flea Infestations ; Reproduction
    ISSN: 00298549
    E-ISSN: 1432-1939
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  • 7
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(10), p.e109677
    Description: Relationships between host and microbial diversity have important ecological and applied implications. Theory predicts that these relationships will depend on the spatio-temporal scale of the analysis and the niche breadth of the organisms in question, but representative data on host-microbial community assemblage in nature is lacking. We employed a natural gradient of rodent species richness and quantified bacterial communities in rodent blood at several hierarchical spatial scales to test the hypothesis that associations between host and microbial species diversity will be positive in communities dominated by organisms with broad niches sampled at large scales. Following pyrosequencing of rodent blood samples, bacterial communities were found to be comprised primarily of broad niche lineages. These communities exhibited positive correlations between host diversity, microbial diversity and the likelihood for rare pathogens at the regional scale but not at finer scales. These findings demonstrate how microbial diversity is affected by host diversity at different spatial scales and suggest that the relationships between host diversity and overall disease risk are not always negative, as the dilution hypothesis predicts.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 8
    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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  • 9
    Language: English
    In: Biological Conservation, September 2017, Vol.213, pp.252-255
    Description: In 2013, the Group on Earth Observations Biodiversity Observation Network (GEO BON) developed the framework of Essential Biodiversity Variables (EBVs), inspired by the Essential Climate Variables (ECVs). The EBV framework was developed to distill the complexity of biodiversity into a manageable list of priorities and to bring a more coordinated approach to observing biodiversity on a global scale. However, efforts to address the scientific challenges associated with this task have been hindered by diverse interpretations of the definition of an EBV. Here, the authors define an EBV as a critical biological variable that characterizes an aspect of biodiversity, functioning as the interface between raw data and indicators. This relationship is clarified through a multi-faceted stock market analogy, drawing from relevant examples of biodiversity indicators that use EBVs, such as the Living Planet Index and the UK Spring Index. Through this analogy, the authors seek to make the EBV concept accessible to a wider audience, especially to non-specialists and those in the policy sector, and to more clearly define the roles of EBVs and their relationship with biodiversity indicators. From this we expect to support advancement towards globally coordinated measurements of biodiversity.
    Keywords: Biodiversity ; Indicator ; Priority Measurement ; Biodiversity Observation Network ; Living Planet Index ; UK Spring Index ; Agriculture ; Biology ; Ecology
    ISSN: 0006-3207
    E-ISSN: 18732917
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  • 10
    In: Methods in Ecology and Evolution, August 2018, Vol.9(8), pp.1787-1798
    Description: Biodiversity includes multiscalar and multitemporal structures and processes, with different levels of functional organization, from genetic to ecosystemic levels. One of the mostly used methods to infer biodiversity is based on taxonomic approaches and community ecology theories. However, gathering extensive data in the field is difficult due to logistic problems, especially when aiming at modelling biodiversity changes in space and time, which assumes statistically sound sampling schemes. In this context, airborne or satellite remote sensing allows information to be gathered over wide areas in a reasonable time. Most of the biodiversity maps obtained from remote sensing have been based on the inference of species richness by regression analysis. On the contrary, estimating compositional turnover (β‐diversity) might add crucial information related to relative abundance of different species instead of just richness. Presently, few studies have addressed the measurement of species compositional turnover from space. Extending on previous work, in this manuscript, we propose novel techniques to measure β‐diversity from airborne or satellite remote sensing, mainly based on: (1) multivariate statistical analysis, (2) the spectral species concept, (3) self‐organizing feature maps, (4) multidimensional distance matrices, and the (5) Rao's Q diversity. Each of these measures addresses one or several issues related to turnover measurement. This manuscript is the first methodological example encompassing (and enhancing) most of the available methods for estimating β‐diversity from remotely sensed imagery and potentially relating them to species diversity in the field.
    Keywords: Β‐Diversity ; Kohonen Self‐Organizing Feature Maps ; Rao'S Q Diversity Index ; Remote Sensing ; Satellite Imagery ; Sparse Generalized Dissimilarity Model ; Spectral Species Concept
    ISSN: 2041-210X
    E-ISSN: 2041-210X
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