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  • 1
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    Associazione Italiana di Telerilevamento (AIT)
    In:  Italian Journal of Remote Sensing, Vol 40, Iss 1, Pp 59-73 (2008)
    Publication Date: 2019-02-21
    Description: ß-diversity is defined as the complementarity in species composition between pairs of sites and plays a crucial role in biodiversity management and conservation, since it allows to detect those environmental gradients that functionally act in determining the variation of species composition. From an ecological viewpoint, the decay of ß-similarity principally arises from: (i) a decrease in environmental similarity with distance, which inevitably creates a competition among species with different physiological abilities (niche difference model); (ii) a spatial configuration which creates spatial barriers and thus isolation among habitats, that influences species and gene movement across landscapes. To date, efforts were made to demonstrate the effect of distance on species similarity. However, few tests have been performed at local scale, i.e. at the community level. The aim of this study is to test the distance decay of ß-similarity hypothesis at local scale (10x10 m plots) considering both (i) spatial distance between pairs of sites; (ii) the ecological distance between pairs of sites, measured as Euclidean distance in vector spaces defined by ecological variables (elevation, aspect, slope, assolation, spectral reflectance considering both the whole multispectral system of a Landsat ETM+ image and the Near Infrared Wavelength, band 4). ß-similarity decay rates at different thresholds (t) have been quantified by means of quantile regressions based on exponential models, focusing on the main factors influencing their trends.
    Keywords: ß-similarity ; distance decay ; Landsat ETM+ ; quantile regressions ; Physical geography ; GB3-5030 ; Geography. Anthropology. Recreation ; G ; DOAJ:Geography ; DOAJ:Earth and Environmental Sciences
    Repository Name: DOAJ Earth and Environmental Sciences
    Type: article
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  • 2
    Publication Date: 2019
    Description: Abstract Questions Despite the increasing scientific interest in distance decay of compositional similarity in ecology, the scale‐dependence of geographical vs environmental control on distance decay of biological communities has not been properly addressed so far. The present work highlights the relative importance of niche‐based processes vs dispersal limitations on distance decay patterns of epilithic bryophyte assemblages at different spatial scales. Location Serra de Sintra, central Portugal. Methods We adopted a nested sampling design with 32 selected sampling sites in each of which two clusters, each with five rocks, were surveyed. Each cluster was characterized by a set of 15 macro‐scale variables, which were divided into environmental and anthropogenic. For each rock eight micro‐scale variables were recorded. Partial Mantel tests were used to assess the relative importance of geographical and environmental distance on community dissimilarity for each grain size (site, cluster, rock). Quantile regressions were used to describe the decay patterns of community similarity with respect to geographical and environmental distances. Ordination analyses and variation partitioning techniques were applied to assess the pure and shared effects of measured variables on bryophyte community composition. Results Environmental distance based upon macro‐scale predictors was significantly correlated to community similarity, while no significant correlation was found for ecological distance calculated for micro‐scale predictors, except at the largest grain size. The decrease of community similarity with geographical and environmental distance was thus consistently strengthened with increasing sample grain. Compositional variation was best explained by anthropogenic variables. Conclusions The relative importance of environmental vs geographical distance on compositional similarity in epilithic bryophyte communities varies with the spatial scale of the predictors and with the sample grain. The decrease of similarity with increasing distance is related to changes in habitat features, especially those driven by human disturbance, while is weakly affected by variations in substrate features. This article is protected by copyright. All rights reserved.
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
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  • 3
    Publication Date: 2019
    Description: Despite that congruence across taxa has been proved as an effective tool to provide insights into the processes structuring the spatial distribution of taxonomic groups and is useful for conservation purposes, only a few studies on cross-taxon congruence focused on freshwater ecosystems and on the relations among vascular plants and lichens. We hypothesized here that, since vascular plants could be good surrogates of lichens in these ecosystems, it would be possible to assess the overall biodiversity of riparian habitats using plant data only. In this frame, we explored the relationship between (a) species richness and (b) community composition of plants and lichens in a wetland area located in central Italy to (i) assess whether vascular plants are good surrogates of lichens and (ii) to test the congruence of patterns of species richness and composition among plants and lichens along an ecological gradient. The general performance of plant species richness per se, as a biodiversity surrogate of lichens, had poor results. Nonetheless, the congruence in compositional patterns between lichens and vascular plants varied across habitats and was influenced by the characteristics of the vegetation. In general, we discussed how the strength of the studied relationships could be influenced by characteristics of the data (presence/absence vs. abundance), by the spatial scale, and by the features of the habitats. Overall, our data confirm that the more diverse and structurally complex the vegetation is, the more diverse are the lichen communities it hosts.
    Electronic ISSN: 1424-2818
    Topics: Biology
    Published by MDPI
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  • 4
    Publication Date: 2017-11-22
    Description: The choice of the best sampling strategy to capture mean values of functional traits for a species/population, while maintaining information about traits’ variability and minimizing the sampling size and effort, is an open issue in functional trait ecology. Intraspecific variability (ITV) of functional traits strongly influences sampling size and effort. However, while adequate information is available about intraspecific variability between individuals (ITV BI ) and among populations (ITV POP ), relatively few studies have analyzed intraspecific variability within individuals (ITV WI ). Here, we provide an analysis of ITV WI of two foliar traits, namely specific leaf area (SLA) and osmotic potential (π), in a population of Quercus ilex L. We assessed the baseline ITV WI level of variation between the two traits and provided the minimum and optimal sampling size in order to take into account ITV WI , comparing sampling optimization outputs with those previously proposed in the literature. Different factors accounted for different amount of variance of the two traits. SLA variance was mostly spread within individuals (43.4% of the total variance), while π variance was mainly spread between individuals (43.2%). Strategies that did not account for all the canopy strata produced mean values not representative of the sampled population. The minimum size to adequately capture the studied functional traits corresponded to 5 leaves taken randomly from 5 individuals, while the most accurate and feasible sampling size was 4 leaves taken randomly from 10 individuals. We demonstrate that the spatial structure of the canopy could significantly affect traits variability. Moreover, different strategies for different traits could be implemented during sampling surveys. We partially confirm sampling sizes previously proposed in the recent literature and encourage future analysis involving different traits. The choice of the best sampling strategy to capture mean values of functional traits for a species/population, while maintaining information about traits’ variability and minimizing the sampling size and effort, is an open issue in functional trait ecology. We assessed the baseline intraspecific variability (ITV wi ) level of variation of two foliar traits, namely SLA and osmotic potential (π), in a population of Quercus ilex L. We demonstrate that the spatial structure of the canopy could significantly affect traits variability and provided the minimum and optimal sampling size in order to take into account ITV wi .
    Electronic ISSN: 2045-7758
    Topics: Biology
    Published by Wiley
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  • 5
    Publication Date: 2019
    Description: Abstract Questions 1) Are there differences in abundance‐weighted functional trait values between native and alien species in coastal plant communities? 2) Which functional traits are associated with a higher level of invasion in these communities? 3) Do functional diversity patterns differ between native and alien species? 4) Is alien species occurrence linked to small‐scale functional homogenization effects on the resident native species?. Location N‐Adriatic coastal ecosystems (Marano and Grado lagoon, Friuli Venezia Giulia region, Italy) Methods We sampled coastal vegetation within two habitats (foredunes and saltmarshes) along 9 belt transects in two sampling sites. Plant species richness and abundance were assessed in 128 plots along with a suite of plant functional traits. We tested for differences in CWMs between native and alien species within the two habitats, and a Linear Mixed Model (LMMs) provided insights on traits fostering the invasion success among alien species. To check for potential functional homogenization driven by alien species invasion, we explored functional diversity patterns of native and alien species (β and γ functional diversity) and the relationship between α functional diversity and alien cover. Results Alien species had lower functional diversity than natives and were characterized by lower leaf construction costs coupled with lower drought resistance and higher water transport efficiency. The most abundant aliens were the ones minimizing carbon investment for leaf construction. In addition, we also found evidence for small‐scale functional homogenization driven by alien invasion. Conclusions Our results suggested that native species adopt a resource conservative strategy whereas alien species are characterized by a higher resource acquisition capacity (i.e. acquisitive strategy). Our data also confirmed that alien species are less functionally diverse than natives, potentially driving the community towards small‐scale functional homogenization, resulting in a loss of species and a reduction in the functional space.
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
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  • 6
    Publication Date: 2019-03-18
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
    Published by Wiley
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  • 7
  • 8
    Publication Date: 2007-02-24
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
    Published by Wiley
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  • 9
    Publication Date: 2007-01-01
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
    Published by Wiley
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