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Berlin Brandenburg

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  • 1
    In: Journal of Biogeography, June 2014, Vol.41(6), pp.1055-1069
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1111/jbi.12299/abstract Byline: Itamar Giladi, Felix May, Michael Ristow, Florian Jeltsch, Yaron Ziv, Kostas Triantis Keywords: Conservation biogeography; extinction debt; habitat fragmentation; habitat islands; island biogeography theory; island ecology; isolation; scale-dependence; species-area relationship; species density Abstract Aim Patterns 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. Location Worldwide (review) and a semi-arid agro-ecosystem in Israel (case study). Methods We 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. Results We 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 conclusions These 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. CAPTION(S): Appendix S1 List of fragments sampled, their attributes, and plant species richness and species density. Appendix S2 List of studies used in the literature review. Appendix S3 Figures showing species-area and species-isolation relationships using an exponential model.
    Keywords: Conservation Biogeography ; Extinction Debt ; Habitat Fragmentation ; Habitat Islands ; Island Biogeography Theory ; Island Ecology ; Isolation ; Scale‐Dependence ; Species–Area Relationship ; Species Density
    ISSN: 0305-0270
    E-ISSN: 1365-2699
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  • 2
    Language: English
    In: Biological Conservation, Nov, 2013, Vol.167, p.349(5)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.biocon.2013.08.028 Byline: Guy Rotem, Yaron Ziv, Itamar Giladi, Amos Bouskila Abstract: acents Reptiles' movement was unidirectional from the natural patches into the wheat fields. acents Individuals in the natural patches were in poorest physical condition. acents All individuals in the field and those movement from the natural patch were adults. acents Wheat fields arthropod abundance was higher compared to that in the natural patches. Article History: Received 27 January 2013; Revised 8 August 2013; Accepted 18 August 2013
    Keywords: Wheat -- Environmental Aspects ; Reptiles -- Environmental Aspects ; Agroecosystems -- Environmental Aspects
    ISSN: 0006-3207
    Source: Cengage Learning, Inc.
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  • 3
    In: Journal of Ecology, March 2014, Vol.102(2), pp.486-495
    Description: Hutchinsonian niche theory posits that organisms have fundamental abiotic resource requirements from which they are limited by competition. Organisms also have fundamental biotic requirements, such as mutualists, for which they also might compete. We test this idea with a widespread ant–plant mutualism. Ant‐mediated seed dispersal (myrmecochory) in eastern North America involves a few ant species that can effectively disperse the seeds of many plant species. This imbalance suggests that ant‐dispersed plants (myrmecochores) might compete for ant dispersers. We hypothesized that, because larger seeds are more attractive to ants, myrmecochores might segregate the timing of seed release by size to relieve competition. Comparative literature analysis across plant species reveals that myrmecochore seed size increases with the fruiting season in a staggered pattern so that small‐ and large‐seeded co‐occurring species do not release seeds at the same time – a pattern not observed in plants using other dispersal modes. We then presented foraging ants with small and large seeds in field trials throughout the fruiting season to test whether the observed temporal segregation in myrmecochore seed size is consistent with plant competition for ant dispersers. Our results show that dispersal rates for smaller seeds increase across the growing season, but only in the absence of large seeds. Our combined literature and field data suggest that myrmecochores stagger fruiting by seed size so that small seeds are set earlier to avoid competition for dispersal mutualists with larger seeds. Synthesis. Ecological interactions are often treated as either positive or negative, but our data blur this distinction by revealing that a positive interaction (mutualism) might be structured by a negative interaction (competition). Moreover, the recognition of biotic resources as critical niche requirements blurs the classic dichotomy between the fundamental (abiotic) versus realized (biotic limited) niche. Ecological interactions are often treated as either positive or negative, but our data blur this distinction by revealing that a positive interaction (mutualism) might be structured by a negative interaction (competition). Moreover, the recognition of biotic resources as critical niche requirements blurs the classic dichotomy between the fundamental (abiotic) versus realized (biotic limited) niche.
    Keywords: Ant–Plant Interactions ; Aphaenogaster ; Biotic Interactions ; Dispersal ; Niche Theory ; Seed Dispersal ; Species Distribution
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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  • 4
    In: Journal of Ecology, March 2014, Vol.102(2), pp.544-554
    Description: Mismatches between species distributions and habitat suitability are predicted by niche theory and have important implications for forecasting how species may respond to environmental changes. Quantifying these mismatches is challenging, however, due to the high dimensionality of species niches and the large spatial and temporal variability in population dynamics. Here, we explore how probabilistic assessments of habitat suitability based on demographic models may be used to better bridge niche theory and population dynamics. We use integral projection models (IPMs) to predict population growth rates for a terrestrial orchid in response to environmental variables. By parameterizing these IPMs with hierarchical models, we develop a spatially variable measure of a species' demographic niche, which can then be compared against its distribution to test ideas about what factors control a species' distribution. We found that demographic suitability of sites was not well correlated with the orchid's distribution at local scales, with many absences from microsites of high predicted suitability and occurrences in sites with low predicted suitability. However, at the population scale, abundance was positively correlated with demographic suitability of the sites. These results are consistent with dispersal limitation and source–sink dynamics at small scales but stronger distribution‐suitability matching at larger landscape scales. Synthesis. The relationships between species distributions and demographic performance underlie basic niche theory and have important implications for predicting responses to a changing environment. The complexities of these relationships will require approaches that can encapsulate what we know in probabilistic terms and allow for spatially varying niche relationships. The relationships between species distributions and demographic performance underlie basic niche theory and have important implications for predicting responses to a changing environment. The complexities of these relationships will require approaches that can encapsulate what we know in probabilistic terms and allow for spatially varying. Editor's Choice
    Keywords: Ayesian ; Demography ; Hierarchical ; Integral Projection Models ; Niche Theory ; Rchidaceae ; Plant–Climate Interactions ; Scale
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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  • 5
    In: Oikos, June 2012, Vol.121(6), pp.942-951
    Description: The response of species diversity to dispersal capability is inherently scale‐dependent: increasing dispersal capability is expected to increase diversity at the local scale, while decreasing diversity at the metacommunity scale. However, these expectations are based on model formulations that neglect dispersal limitation and species segregation at the local scale. We developed a unifying framework of dispersal–diversity relationships and tested the generality of these expectations. For this purpose we used a spatially‐explicit neutral model with various combinations of survey area (local scale) and landscape size (metacommunity scale). Simulations were conducted using landscapes of finite and of conceptually infinite size. We analyzed the scale‐dependence of dispersal‐diversity relationships for exponentially‐bounded versus fat‐tailed dispersal kernels, several levels of speciation rate and contrasting assumptions on recruitment at short dispersal distances. We found that the ratio of survey area to landscape size is a major determinant of dispersal–diversity relationships. With increasing survey‐to‐landscape area ratio the dispersal–diversity relationship switches from monotonically increasing through a U‐shaped pattern (with a local minimum) to a monotonically decreasing pattern. Therefore, we provide a continuous set of dispersal–diversity relationships, which contains the response shapes reported previously as extreme cases. We suggest the mean dispersal distance with the minimum of species diversity (minimizing dispersal distance) for a certain scenario as a key characteristic of dispersal–diversity relationships. We show that not only increasing mean dispersal distances, but also increasing variances of dispersal can enhance diversity at the local scale, given a diverse species pool at the metacommunity scale. In conclusion, the response of diversity to variations of dispersal capability at spatial scales of interest, e.g. conservation areas, can differ more widely than expected previously. Therefore, land use and conservation activities, which manipulate dispersal capability, need to consider the landscape context and potential species pools carefully.
    Keywords: Biological Diversity ; Landscape Ecology ; Community Ecology ; Conservation Biology;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 6
    In: Oikos, March 2006, Vol.112(3), pp.481-492
    Description: Myrmecochory, or seed dispersal by ants, is a dispersal syndrome found among several thousand plant species occupying different ecosystems and geographical regions. Typically, ants benefit from consuming a lipid‐rich appendage on the seed and in return provide seed dispersal service to the plant. Several hypotheses have been proposed to explain the selective advantage for plants resulting from myrmecochory, including directed dispersal, dispersal for distance and escape from seed predators. I contrast the evidence available in the literature for these hypotheses and distinguish the studies on the basis of ecosystem and plant growth forms. The predator‐avoidance and the distance dispersal hypotheses were supported in most studies that addressed them, and the directed dispersal hypothesis was supported in about half of the studies that tested it. Multiple hypotheses were supported in most studies that tested more than one hypothesis, suggesting that the various selective advantages conferred from myrmecochory are seldom exclusive. I also review evidence for the hypothesis that plants have evolved adaptations both for selecting seed dispersers and for manipulating the behavior of those dispersers. Based on this evidence, I argue that focusing future research on the evolution of partner choice by myrmecochores and its effects on the overall plant fitness will be more fruitful than putting an emphasis on classifying the selective advantage to plants into distinct categories and test for their existence separately.
    Keywords: Environmental Sciences ; Biology ; Ecology;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 7
    In: Journal of Ecology, January 2013, Vol.101(1), pp.97-106
    Description: Shrubs in arid and semi‐arid ecosystems are often associated with three distinct patch types: the shrub core, the shrub periphery and surrounding open patches. The distribution of herbaceous seeds in such a patchy system exhibits a well‐documented spatial heterogeneity. However, the mechanisms that generate this heterogeneity are poorly understood, not least because of the difficulty of separating possible effects of the shrub on seed production (via the shrub's modification of resource distribution), seed dispersal and post‐dispersal processes. We used a well‐studied system dominated by a common east Mediterranean shrub (Sarcopoterium spinosum) to directly test the effect of shrubs on herbaceous community seed dispersal. We clipped all potential herbaceous seed sources from plots with or without a shrub at their centre, designated ‘shrub’ or ‘open’, respectively. Seed rain was then sampled over a 7‐month period, along four directions within a fine‐scale radial sampling pattern from the shrub core to its periphery and in corresponding positions in the open plots. Seed predation was monitored likewise. The overall abundance and species richness of herbaceous seeds were similar at all distances from the core in the open plots and at the shrub periphery, but lower under the shrub canopy. However, the observed patterns were clearly directional, with the highest seed abundance and species richness found on the upslope periphery of the shrub patch. These patterns were observed after the elimination of all within‐patch herbaceous seed sources, which suggests that the movement of seeds was mainly driven by gravity‐related mechanisms whose effect was modified by the shrubs. Synthesis. A shrub can function simultaneously as both a seed trap and a barrier to herbaceous seed flow, with the exact balance determined by location within the patch. Furthermore, whether the effect of the shrub on herbaceous seeds is regarded as facilitatory or competitive is scale‐dependent. A mechanistic dissociation of seed dispersal from other processes modulated by the shrub in shaping the herbaceous community, as done in this study, is important for understanding the resilience of semi‐arid and arid ecosystems to environmental changes, especially to the increasingly observed drought‐induced mortality of shrubs associated with climate change. We demonstrate that a shrub can function simultaneously as both a seed trap and a barrier to herbaceous seed flow, with the exact balance determined by location within the shrub patch. Furthermore, whether the effect of the shrub on herbaceous seeds is regarded as facilitatory or competitive is scale‐dependent. A mechanistic dissociation of seed dispersal from other processes modulated by the shrub in shaping the herbaceous community is important for understanding the resilience of semiarid and arid ecosystems to environmental changes.
    Keywords: Dispersal Mode ; Ecosystem Engineer ; Facilitation ; Ground Rolling ; Sarcopoterium Spinosum ; Seed Dispersal ; Seed Trapping
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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  • 8
    In: Journal of Ecology, September 2010, Vol.98(5), pp.1178-1185
    Description:  Whereas classic niche theory is based on the contraction of the niche via negative interactions, facilitative niche theory suggests that mutualisms can expand the niche via positive interactions. Specifically, animal‐mediated seed dispersal can expand the utilization of physical space by plants and allow greater access to resources and other environmental requirements. Ant‐mediated dispersal of plant propagules (myrmecochory) is a common mutualism throughout the world, particularly in the deciduous forests of the eastern United States where this research is conducted.  We examine two facets of niche expansion via ant‐mediated seed dispersal: (1) increased utilization of resources along resource gradients and (2) escape from unfavourable density‐dependent conditions.  We test these assumptions by introducing seeds in cafeteria‐style bait stations along abiotic gradients (moisture, temperature, light) for removal by key seed dispersers from the ant genus . We also examine plant aggregation along the same gradients.  Ant‐mediated dispersal services decrease significantly with increasing soil moisture and ultimately fail at levels that are demonstratively within the plant’s niche optima; further, the decline in dispersal services is correlated with increasing plant aggregation, suggesting that enemy escape also falters at relatively high levels of soil moisture.  . Facilitated propagule dispersal fails to expand the niche in either enhanced resource utilization or decreased density dependence as the niche requirements for the ant disperser are nested within those for the plant. The strength of this interaction varies across space and time, and in doing so may undermine attempts to predict future distributions. Further, given that myrmecochores are typically poor dispersers, the incomplete niche overlap between the plant and its facilitator makes this plant guild particularly susceptible to climatic change if each participant responds individually to shifting environmental conditions.
    Keywords: Sp. ; Biotic Interactions ; Dispersal ; Facilitation ; Fundamental Niche ; Hexastylis Arifolia ; Physiological Limitation ; Realized Niche ; Species Distribution
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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  • 9
    Language: English
    In: Biological conservation, 2013, Vol.167, pp.349-353
    Description: 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. ; p. 349-353.
    Keywords: Wheat ; Agroecosystems ; Biodiversity ; Habitats ; Pitfall Traps ; Body Condition ; Habitat Preferences ; Wildlife ; Spring ; Reptiles ; Arthropods ; Human Population ; Adults
    ISSN: 0006-3207
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 10
    Language: English
    In: Biological Conservation, November 2013, Vol.167, pp.349-353
    Description: 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 , 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 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.
    Keywords: Agroecosystem ; Dispersal ; Ecological Trap ; Fragmentation ; Habitat Selection ; Trachylepis Vittata ; Agriculture ; Biology ; Ecology
    ISSN: 0006-3207
    E-ISSN: 18732917
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