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Dengler J.,University of Bayreuth | Dengler J.,Synthesis Center sDiv | Janisova M.,Slovak Academy of Sciences | Torok P.,Debrecen University | And 2 more authors.
Agriculture, Ecosystems and Environment | Year: 2014

This article introduces a Special Issue on biodiversity of Palaearctic grasslands and provides a synthesis of the current knowledge on this topic. Four major categories of grasslands can be distinguished in the Palaearctic biogeographic realm: (a) zonal steppes (in areas too dry for forests), (b) arctic-alpine grasslands (in areas too cold for forests), (c) azonal and extrazonal grasslands (where hydrology, soil conditions, relief or natural disturbances within the forest biomes prevent tree growth locally) and (d) secondary grasslands (which replace natural forests in consequence of human land use). We summarize the present knowledge about species richness patterns (mainly of vascular plants) along abiotic and land use gradients. Further, we highlight the usefulness of diversity measures not based on species richness, namely functional diversity, phylogenetic diversity and within-species diversity. The strong differences observed for diversity patterns according to analyzed biodiversity parameter, spatial scale or taxonomic group call for comparative studies and caution when generalizing results. A particular challenge are the extreme plot-scale species richness values found in grasslands of a few European regions. We propose a conceptual model that explains the findings by an interplay of various factors acting at different levels: (i) The largest species pool is expected for habitats under conditions that prevailed over the last few million years, with a slight shift towards intermediate positions, i.e. for the Palaearctic in open, semi-dry, base-rich situations. (ii) The landscape-level species pool is increased by continuity of a grassland patch in space and time and heterogeneity of the surrounding landscape. (iii) The coexistence of regionally available species at a plot scale is due to reduced competitive exclusion according to Intermediate Disturbance Hypothesis, mowing once a year without fertilization being particularly effective. Ecosystem functions and services of Palaearctic grasslands are often positively connected to their biodiversity. At the same time, these communities and their biota are nowadays highly endangered. The semi-natural (High Nature Value) grasslands of Europe are mainly threatened by agricultural intensification or abandonment on low-productive sites in remote areas, while the natural steppes of the Palaearctic have largely been destroyed by conversion into arable land. Finally, we present some promising conservation and management approaches and call for a strong and comprehensive Convention on Grassland Conservation. © 2013 Elsevier B.V. Source


Toth K.,Debrecen University | Bogyo D.,Hortobagy National Park Directorate | Valko O.,Mta Of Biodiversity And Ecosystem Services Research Group
Plant Ecology | Year: 2016

Recent studies found that endozoochorous seed dispersal by waterfowl is an important dispersal strategy for numerous plants. With a germination experiment, we evaluated the endozoochorous dispersal potential of the endangered Lesser White-fronted Goose (LWfG, Anser erythropus) and larger goose species (A. anser and A. albifrons) in their autumn and spring staging areas (Hortobágy, East Hungary). We tested the following hypotheses: (1) the amount and species composition of germinable seeds in the droppings of the habitat specialist LWfG and generalist larger goose species have a different species composition, (2) droppings contain less germinable seeds and less species in spring than in autumn, when most species disperse their seeds. We collected droppings of LWfG and larger goose species in their feeding habitats in spring and autumn staging areas. Droppings were concentrated and germinated on trays filled with steam-sterilised soil in a greenhouse. LWfG dispersed more species typical to alkali habitats and lower amounts of weeds compared to larger goose species, which confirmed our first hypothesis. We recorded higher total species numbers and species number of annuals, wetland species and weeds in autumn, which supported our second hypothesis. We found that the studied goose species used a wide range of feeding habitats; thus, they can play an important role in dispersing seeds between a range of habitats which they use for feeding. Based on the seed content of the droppings, LWfG is confined to natural habitats; thus, for the effective protection of this vulnerable species, it is crucial to preserve natural feeding habitats in their staging areas. © 2016, Springer Science+Business Media Dordrecht. Source


Lakatos K.T.,Debrecen University | Laszlo Z.,Babes - Bolyai University | Tothmeresz B.,Mta Of Biodiversity And Ecosystem Services Research Group
Acta Oecologica | Year: 2016

The introduced black locust (Robinia pseudoacacia) has become an invasive plant species in Europe. The introduction of alien plants such as the black locust may modify ecosystem composition and functioning. In response to the presence of a potential host plant, herbivores can adapt and shift to the consumption of the new host plant. In Eastern-Central Europe, the seed predator Bruchophagus robiniae (Hymenoptera: Eurytomidae) is an important consumer of black locust seeds which presumably shifted from its formerly host species to black locust. We tested the influence of host plant abundance on a seed predator - parasitoid community. We found that the seed predator B. robiniae was present in higher numbers in woodlots than in small patches of black locust. The density of the specialist parasitoid Mesopolobus sp. was lower in woodlots than in small patches, while the generalist parasitoid Eupelmus urozonos was evenly distributed between woodlots and small patches of black locust. We found that parasitoid species are influenced by the patch size of host plants, thus characteristics of introduced host plants can also manifest in higher trophic levels. © 2016 Elsevier Masson SAS. Source


Valko O.,Mta Of Biodiversity And Ecosystem Services Research Group | Tothmeresz B.,Debrecen University | Kelemen A.,Debrecen University | Simon E.,Debrecen University | And 3 more authors.
Agriculture, Ecosystems and Environment | Year: 2014

For an effective conservation and management in grasslands it is essential to understand mechanisms sustaining biodiversity. To gain knowledge is especially crucial in stressed grasslands harbouring a unique flora and fauna, like alkali grasslands. Aboveground vegetation, seed bank and environmental factors were studied in three stands of the following alkali grassland types: (i) Artemisia dry alkali grasslands at highest elevations; (ii) Puccinellia high and (iii) Puccinellia low grasslands at medium to low elevations, and (iv) Juncus wet alkali grasslands at the lowest elevations. We tested the following hypotheses: (i) Seed bank species diversity and density are the highest in the most stressed grassland types, where regeneration by seeds could have a major importance in sustaining vegetation diversity. (ii) Seed bank density of hygrophytes increases with decreasing elevation, because the cover of hygrophytes in the vegetation increases with decreasing elevation. The mean seed bank density ranged from 30,104 up to 51,410seeds/m2, which is higher than in most dry grasslands. Both the lowest seed bank density and diversity were detected in the most stressed Puccinellia high grasslands; Spergularia salina was the only abundant seed bank species (possessing at least 1000seeds/m2). These results not supported our first hypothesis. We detected the highest seed densities of almost all hygrophyte species in the lowest-elevated Juncus grasslands. But, we did not find a significant monotonous correlation between elevation and the overall hygrophyte seed bank density; because most of the hygrophyte species were missing from the seed bank at the medium-elevated, but most saline Puccinellia grasslands. Thus, our results only partly supported the second hypothesis. In total we detected more species in the seed bank than in the aboveground vegetation which emphasises that seed bank plays an important role in sustaining the diversity of alkali grasslands. However, characteristic graminoids possessed no considerable seed bank, except for Juncus compressus (up to 38,619seeds/m2). We can conclude that persistence and establishment of most alkali grassland species are not supported by the local persistent seed bank. © 2013 Elsevier B.V. Source


Laszlo Z.,Babes - Bolyai University | Baur H.,Abteilung Wirbellose Tiere | Tothmeresz B.,Mta Of Biodiversity And Ecosystem Services Research Group
Systematic Entomology | Year: 2013

We demonstrate by multivariate ratio analysis (MRA) the validity of two female colour morphs as separate species in what was previously regarded as a single species, Trigonoderus cyanescens (Förster, 1841) (Hymenoptera: Pteromalidae). As a result, T.pedicellaris Thomson, 1878 stat.r., is resurrected from synonymy under T.cyanescens and T.filatus binubilatus Erdos, 1960 syn.n. is synonymized with T.cyanescens. More than 20 characters were measured as part of two MRA dataset analyses. The first analysis excluded all measurements related to the gaster, whereas the second included gaster length, gaster breadth and seventh gaster tergite breadth. The first analysis revealed that the best separating morphometric ratios for the two species are head breadth:metatibia length and OOL:parastigma length, whereas the second analysis revealed OOL:gaster length as the second best separating ratio. The measurement error of all characters was below the admissible level of 30%. Gaster length proved to be a good character for separating the two groups, showed the lowest measurement error, and its percentage coefficient of variation was not greater than for other characters. This indicates that gaster length should not be discarded out-of-hand as a morphometric character in Pteromalidae. The variables that gave the best separating ratios included different body parts; therefore we suggest that the body of a specimen should be taken as a whole for use in MRA analyses, where each distance measurement can interact freely with any other. A key, figures and re-descriptions of T.cyanescens and T.pedicellaris are provided. © 2013 The Royal Entomological Society. Source

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