TY - JOUR A1 - Rabovsky, Milena A1 - Schad, Daniel A1 - Abdel Rahman, Rasha T1 - Semantic richness and density effects on language production BT - Electrophysiological and behavioral evidence JF - Journal of experimental psychology : Learning, memory, and cognition N2 - Language production ultimately aims to convey meaning. Yet words differ widely in the richness and density of their semantic representations, and these differences impact conceptual and lexical processes during speech planning. Here, we replicated the recent finding that semantic richness, measured as the number of associated semantic features according to semantic feature production norms, facilitates object naming. In contrast, intercorrelational semantic feature density, measured as the degree of intercorrelation of a concept's features, presumably resulting in the coactivation of closely related concepts, has an inhibitory influence. We replicated the behavioral effects and investigated their relative time course and electrophysiological correlates. Both the facilitatory effect of high semantic richness and the inhibitory influence of high feature density were reflected in an increased posterior positivity starting at about 250 ms, in line with previous reports of posterior positivities in paradigms employing contextual manipulations to induce semantic interference during language production. Furthermore, amplitudes at the same posterior electrode sites were positively correlated with object naming times between about 230 and 380 ms. The observed effects follow naturally from the assumption of conceptual facilitation and simultaneous lexical competition and are difficult to explain by language production theories dismissing lexical competition. KW - picture naming KW - ERPs KW - semantic richness KW - semantic features KW - lexical KW - competition Y1 - 2021 U6 - https://doi.org/10.1037/xlm0000940 SN - 0278-7393 SN - 1939-1285 VL - 47 IS - 3 SP - 508 EP - 517 PB - American Psychological Association CY - Washington ER - TY - JOUR A1 - Gebser, Martin A1 - Maratea, Marco A1 - Ricca, Francesco T1 - The Seventh Answer Set Programming Competition BT - design and results JF - Theory and practice of logic programming N2 - Answer Set Programming (ASP) is a prominent knowledge representation language with roots in logic programming and non-monotonic reasoning. Biennial ASP competitions are organized in order to furnish challenging benchmark collections and assess the advancement of the state of the art in ASP solving. In this paper, we report on the design and results of the Seventh ASP Competition, jointly organized by the University of Calabria (Italy), the University of Genova (Italy), and the University of Potsdam (Germany), in affiliation with the 14th International Conference on Logic Programming and Non-Monotonic Reasoning (LPNMR 2017). KW - Answer Set Programming KW - competition Y1 - 2019 U6 - https://doi.org/10.1017/S1471068419000061 SN - 1471-0684 SN - 1475-3081 VL - 20 IS - 2 SP - 176 EP - 204 PB - Cambridge Univ. Press CY - Cambridge [u.a.] ER - TY - JOUR A1 - Schirmer, Annika A1 - Hoffmann, Julia A1 - Eccard, Jana A1 - Dammhahn, Melanie T1 - My niche BT - individual spatial niche specialization affects within- and between-species interactions JF - Proceedings of the Royal Society of London : B, Biological sciences N2 - Intraspecific trait variation is an important determinant of fundamental ecological interactions. Many of these interactions are mediated by behaviour. Therefore, interindividual differences in behaviour should contribute to individual niche specialization. Comparable with variation in morphological traits, behavioural differentiation between individuals should limit similarity among competitors and thus act as a mechanism maintaining within-species variation in ecological niches and facilitating species coexistence. Here, we aimed to test whether interindividual differences in boldness covary with spatial interactions within and between two ecologically similar, co-occurring rodent species (Myodes glareolus, Apodemus agrarius). In five subpopulations in northeast Germany, we quantified individual differences in boldness via repeated standardized tests and spatial interaction patterns via capture-mark- recapture (n = 126) and automated VHF telemetry (n = 36). We found that boldness varied with space use in both species. Individuals of the same population occupied different spatial niches, which resulted in non-random patterns of within- and between-species spatial interactions. Behavioural types mainly differed in the relative importance of intra- versus interspecific competition. Within-species variation along this competition gradient could contribute to maintaining individual niche specialization. Moreover, behavioural differentiation between individuals limits similarity among competitors, which might facilitate the coexistence of functionally equivalent species and, thus, affect community dynamics and local biodiversity. KW - animal personality KW - competition KW - individual niche specialization KW - movement ecology KW - coexistence KW - small mammals Y1 - 2020 U6 - https://doi.org/10.1098/rspb.2019.2211 SN - 0962-8452 SN - 1471-2954 VL - 287 IS - 1918 PB - Royal Society CY - London ER - TY - JOUR A1 - Heinze, Johannes T1 - Herbivory by aboveground insects impacts plant root morphological traits JF - Plant ecology : an international journal N2 - Aboveground herbivory induces physiological responses, like the release of belowground chemical defense and storage of secondary metabolites, as well as physical responses in plants, like increased root biomass production. However, studies on effects of aboveground herbivory on root morphology are scarce and until now no study tested herbivory effects under natural conditions for a large set of plant species. Therefore, in a field experiment on plant-soil interactions, I investigated the effect of aboveground insect herbivory on root morphological traits of 20 grassland plant species. For 9 of the 20 species, all individuals showed shoot damage in the presence of insect herbivores, but no damage in insect herbivore exclusions. In these 9 species root biomass increased and root morphological traits changed under herbivory towards thinner roots with increased specific root surface. In contrast, the remaining species did not differ in the number of individuals damaged, root biomass nor morphological traits with herbivores present vs. absent. The fact that aboveground herbivory resulted in thinner roots with increased specific root surface area for all species in which the herbivore exclusion manipulation altered shoot damage might indicate that plants increase nutrient uptake in response to herbivory. However, more importantly, results provide empirical evidence that aboveground herbivory impacts root morphological traits of plants. As these traits are important for the occupation of soil space, uptake processes, decomposition and interactions with soil biota, results suggest that herbivory-induced changes in root morphology might be of importance for plant-soil feedbacks and plant-plant competition. KW - herbivory KW - root traits KW - specific root length KW - specific root surface KW - area KW - plant-soil feedback KW - competition Y1 - 2020 U6 - https://doi.org/10.1007/s11258-020-01045-w SN - 1385-0237 SN - 1573-5052 VL - 221 IS - 8 SP - 725 EP - 732 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - van Velzen, Ellen T1 - Predator coexistence through emergent fitness equalization JF - Ecology : a publication of the Ecological Society of America N2 - The competitive exclusion principle is one of the oldest ideas in ecology and states that without additional self-limitation two predators cannot coexist on a single prey. The search for mechanisms allowing coexistence despite this has identified niche differentiation between predators as crucial: without this, coexistence requires the predators to have exactly the same R* values, which is considered impossible. However, this reasoning misses a critical point: predators' R* values are not static properties, but affected by defensive traits of their prey, which in turn can adapt in response to changes in predator densities. Here I show that this feedback between defense and predator dynamics enables stable predator coexistence without ecological niche differentiation. Instead, the mechanism driving coexistence is that prey adaptation causes defense to converge to the value where both predators have equal R* values ("fitness equalization"). This result is highly general, independent of specific model details, and applies to both rapid defense evolution and inducible defenses. It demonstrates the importance of considering long-standing ecological questions from an eco-evolutionary viewpoint, and showcases how the effects of adaptation can cascade through communities, driving diversity on higher trophic levels. These insights offer an important new perspective on coexistence theory. KW - coexistence KW - competition KW - competitive exclusion KW - defense KW - eco-evolutionary feedbacks KW - emergent facilitation KW - predator KW - prey KW - dynamics Y1 - 2020 U6 - https://doi.org/10.1002/ecy.2995 SN - 0012-9658 SN - 1939-9170 VL - 101 IS - 5 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Boch, Steffen A1 - Müller, Jörg A1 - Prati, Daniel A1 - Fischer, Markus T1 - Low-intensity management promotes bryophyte diversity in grasslands JF - Tuexenia : Mitteilungen der Floristisch-Soziologischen Arbeitsgemeinschaft N2 - Bryophytes constitute an important and permanent component of the grassland flora and diversity in Europe. As most bryophyte species are sensitive to habitat change, their diversity is likely to decline following land-use intensification. Most previous studies on bryophyte diversity focused on specific habitats of high bryophyte diversity, such as bogs, montane grasslands, or calcareous dry grasslands. In contrast, mesic grasslands are rarely studied, although they are the most common grassland habitat in Europe. They are secondary vegetation, maintained by agricultural use and thus, are influenced by different forms of land use. We studied bryophyte species richness in three regions in Germany, in 707 plots of 16 m(2) representing different land-use types and environmental conditions. Our study is one of the few to inspect the relationships between bryophyte richness and land use across contrasting regions and using a high number of replicates. Among the managed grasslands, pastures harboured 2.5 times more bryophyte species than meadows and mown pastures. Similarly, bryophyte cover was about twice as high in fallows and pastures than in meadows and mown pastures. Among the pastures, bryophyte species richness was about three times higher in sheep grazed plots than in the ones grazed by cattle or horses. In general, bryophyte species richness and cover was more than 50% lower in fertilized than in unfertilized plots. Moreover, the amount of suitable substrates was linked to bryophyte diversity. Species richness of bryophytes growing on stones increased with stone cover, and the one of bryophytes growing on bark and deadwood increased with larger values of woody plant species and deadwood cover. Our findings highlight the importance of low-intensity land use and high structural heterogeneity for bryophyte conservation. They also caution against an intensification of traditionally managed pastures. In the light of our results, we recommend to maintain low-intensity sheep grazing on sites with low productivity, such as slopes on shallow soils. T2 - Extensive Landnutzung fördert die Moosdiversität im Grünland KW - biodiversity exploratories KW - competition KW - dry and mesic grasslands KW - grazing KW - fertilization KW - land use KW - liverwort KW - meadow KW - moss KW - pasture Y1 - 2018 U6 - https://doi.org/10.14471/2018.38.014 SN - 0722-494X IS - 38 SP - 311 EP - 328 PB - Floristisch-Soziologische Arbeitsgemeinschaft CY - Göttingen ER - TY - JOUR A1 - Heger, Tina A1 - Nikles, Gabriele A1 - Jacobs, Brooke S. T1 - Differentiation in native as well as introduced ranges BT - germination reflects mean and variance in cover of surrounding vegetation JF - AoB PLANTS N2 - Germination, a crucial phase in the life cycle of a plant, can be significantly influenced by competition and facilitation. The aim of this study was to test whether differences in cover of surrounding vegetation can lead to population differentiation in germination behaviour of an annual grassland species, and if so, whether such a differentiation can be found in the native as well as in the introduced range. We used maternal progeny of Erodium cicutarium previously propagated under uniform conditions that had been collected in multiple populations in the native and two introduced ranges, in populations representing extremes in terms of mean and variability of the cover of surrounding vegetation. In the first experiment, we tested the effect of germination temperature and mean cover at the source site on germination, and found interlinked effects of these factors. In seeds from one of the introduced ranges (California), we found indication for a 2-fold dormancy, hindering germination at high temperatures even if physical dormancy was broken and water was available. This behaviour was less strong in high cover populations, indicating cross-generational facilitating effects of dense vegetation. In the second experiment, we tested whether spatial variation in cover of surrounding vegetation has an effect on the proportion of dormant seeds. Contrary to our expectations, we found that across source regions, high variance in cover was associated with higher proportions of seeds germinating directly after storage. In all three regions, germination seemed to match the local environment in terms of climate and vegetation cover. We suggest that this is due to a combined effect of introduction of preadapted genotypes and local evolutionary processes. KW - Bet-hedging KW - competition KW - eco-evolutionary experience KW - facilitation KW - genetic adaptation KW - physical and physiological dormancy KW - preadaptation Y1 - 2018 U6 - https://doi.org/10.1093/aobpla/ply009 SN - 2041-2851 VL - 10 IS - 1 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Lachmuth, Susanne A1 - Henrichmann, Colette A1 - Horn, Juliane A1 - Pagel, Jörn A1 - Schurr, Frank M. T1 - Neighbourhood effects on plant reproduction BT - an experimental-analytical framework and its application to the invasive Senecio inaequidens JF - The journal of ecology N2 - Density dependence is of fundamental importance for population and range dynamics. Density-dependent reproduction of plants arises from competitive and facilitative plant-plant interactions that can be pollination independent or pollination mediated. In small and sparse populations, conspecific density dependence often turns from negative to positive and causes Allee effects. Reproduction may also increase with heterospecific density (community-level Allee effect), but the underlying mechanisms are poorly understood and the consequences for community dynamics can be complex. Allee effects have crucial consequences for the conservation of declining species, but also the dynamics of range edge populations. In invasive species, Allee effects may slow or stop range expansion. Observational studies in natural plant communities cannot distinguish whether reproduction is limited by pollination-mediated interactions among plants or by other neighbourhood effects (e.g. competition for abiotic resources). Even experimental pollen supply cannot distinguish whether variation in reproduction is caused by direct density effects or by plant traits correlated with density. Finally, it is unknown over which spatial scales pollination-mediated interactions occur. To circumvent these problems, we introduce a comprehensive experimental and analytical framework which simultaneously (1) manipulates pollen availability and quality by hand pollination and pollinator exclusion, (2) manipulates neighbourhoods by transplanting target plants, and (3) analyses the effects of con- and heterospecific neighbourhoods on reproduction with spatially explicit trait-based neighbourhood models. Synthesis. By manipulating both pollen availability and target plant locations within neighbourhoods, we can comprehensively analyse spatially explicit density dependence of plant reproduction. This experimental approach enhances our ability to understand the dynamics of sparse populations and of species geographical ranges. KW - Allee effect KW - biological invasion KW - competition KW - density dependence KW - facilitation KW - plant-plant interactions KW - pollination KW - reproductive success KW - spatially explicit model KW - trait-based neighbourhood model Y1 - 2017 U6 - https://doi.org/10.1111/1365-2745.12816 SN - 0022-0477 SN - 1365-2745 VL - 106 IS - 2 SP - 761 EP - 773 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Yannelli, Florencia A. A1 - Karrer, Gerhard A1 - Hall, Rea A1 - Kollmann, Johannes A1 - Heger, Tina T1 - Seed density is more effective than multi-trait limiting similarity in controlling grassland resistance against plant invasions in mesocosms JF - Applied vegetation science : official organ of the International Association for Vegetation Science N2 - QuestionDisturbed areas offer great opportunities for restoring native biodiversity, but they are also prone to invasion by alien plants. Following the limiting similarity hypothesis, we address the question of whether or not similarity of plant functional traits helps developing seed mixtures of native communities with high resistance to invasive species at an early stage of restoration. LocationCentre of Greenhouses and Laboratories Durnast, Technische Universitat Munchen, Freising, Germany. MethodsUsing a system of linear equations, we designed native communities maximizing the similarity between the native and two invasive species according to ten functional traits. We used native grassland plants, two invasive alien species that are often problematic in disturbed areas (i.e., Ambrosia artemisiifolia and Solidago gigantea) and trait information obtained from databases. The two communities were then tested for resistance against establishment of the two invaders separately in a greenhouse experiment. We measured height of the invasive species and above-ground biomass, along with leaf area index, 4 and 8months after sowing respectively. ResultsBoth invasive species were successfully reduced by the native community designed to suppress S. gigantea dominated by small-seeded species. These results could be considered as partial support for the limiting similarity hypothesis. However, given the success of this mixture against both invasive species, suppression was better explained by a seed density effect resulting from the smaller seed mass of the native species included in this mixture. Further, the dominance of a fast-developing competitive species could also contribute to its success. ConclusionsThere was no unequivocal support for the limiting similarity hypothesis in terms of the traits selected. Instead we found that increasing seeding density of native species and selecting species with a fast vegetative development is an effective way to suppress invasive plants during early stages of restoration. If limiting similarity is used to design communities for restoration, early life-history traits should be taken into account. KW - Achillea millefolium KW - Ambrosia artemisiifolia KW - biotic resistance KW - competition KW - density-driven suppression KW - disturbed areas KW - restoration KW - seed mixtures KW - Solidago gigantea Y1 - 2018 U6 - https://doi.org/10.1111/avsc.12373 SN - 1402-2001 SN - 1654-109X VL - 21 IS - 3 SP - 411 EP - 418 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Moustakas, Aristides A1 - Günther, Matthias A1 - Wiegand, Kerstin A1 - Müller, Karl-Heinz A1 - Ward, David A1 - Meyer, Katrin M. A1 - Jeltsch, Florian T1 - Long-term mortality patterns of the deep-rooted Acacia erioloba BT - The middle class shall die! JF - Journal of vegetation science N2 - Question: Is there a relationship between size and death in the Iona-lived, deep-rooted tree, Acacia erioloba, in a semi-arid savanna? What is the size-class distribution of A. erioloba mortality? Does the mortality distribution differ from total tree size distribution? Does A. erioloba mortality distribution match the mortality distributions recorded thus far in other environments? Location: Dronfield Ranch, near Kimberley, Kalahari, South Africa. Methods: A combination of aerial photographs and a satellite image covering 61 year was used to provide long-term spatial data on mortality. We used aerial photographs of the study area from 1940, 1964, 1984, 1993 and a satellite image from 2001 to follow three plots covering 510 ha. We were able to identify and individually follow ca. 3000 individual trees from 1940 till 2001. Results: The total number of trees increased over time. No relationship between total number of trees and mean tree size was detected. There were no trends over time in total number of deaths per plot or in size distributions of dead trees. Kolmogorov-Smirnov tests showed no differences in size class distributions for living trees through time. The size distribution of dead trees was significantly different from the size distribution of all trees present on the plots. Overall, the number of dead trees was low in small size classes, reached a peak value when canopy area was 20 - 30 m(2), and declined in lamer size-classes. Mortality as a ratio of dead vs. total trees peaked at intermediate canopy sizes too. Conclusion: A. erioloba mortality was size-dependent, peaking at intermediate sizes. The mortality distribution differs from all other tree mortality distributions recorded thus far. We suggest that a possible mechanism for this unusual mortality distribution is intraspecific competition for water in this semi-arid environment. KW - competition KW - long-term data KW - remote sensing KW - savanna KW - size dependent mortality KW - size distribution KW - tree death Y1 - 2006 U6 - https://doi.org/10.1111/j.1654-1103.2006.tb02468.x SN - 1100-9233 VL - 17 SP - 473 EP - 480 PB - Blackwell CY - Malden ER -