TY - JOUR A1 - Caron, Maria Mercedes A1 - De Frenne, Pieter A1 - Brunet, Jörg A1 - Chabrerie, Olivier A1 - Cousins, Sara A. O. A1 - Decocq, Guillaume A1 - Diekmann, Martin A1 - Graae, Bente Jessen A1 - Heinken, Thilo A1 - Kolb, Annette A1 - Lenoir, Jonathan A1 - Naaf, Tobias A1 - Plue, Jan A1 - Selvi, Federico A1 - Wulf, Monika A1 - Verheyen, Kris T1 - Divergent regeneration responses of two closely related tree species to direct abiotic and indirect biotic effects of climate change JF - Forest ecology and management N2 - Changing temperature and precipitation can strongly influence plant reproduction. However, also biotic interactions might indirectly affect the reproduction and recruitment success of plants in the context of climate change. Information about the interactive effects of changes in abiotic and biotic factors is essential, but still largely lacking, to better understand the potential effects of a changing climate on plant populations. Here we analyze the regeneration from seeds of Acer platanoides and Acer pseudoplatanus, two currently secondary forest tree species from seven regions along a 2200 km-wide latitudinal gradient in Europe. We assessed the germination, seedling survival and growth during two years in a common garden experiment where temperature, precipitation and competition with the understory vegetation were manipulated. A. platanoides was more sensitive to changes in biotic conditions while A. pseudoplatanus was affected by both abiotic and biotic changes. In general, competition reduced (in A. platanoides) and warming enhanced (in A. pseudoplatanus) germination and survival, respectively. Reduced competition strongly increased the growth of A. platanoides seedlings. Seedling responses were independent of the conditions experienced by the mother tree during seed production and maturation. Our results indicate that, due to the negative effects of competition on the regeneration of A. platanoides, it is likely that under stronger competition (projected under future climatic conditions) this species will be negatively affected in terms of germination, survival and seedling biomass. Climate-change experiments including both abiotic and biotic factors constitute a key step forward to better understand the response of tree species' regeneration to climate change. (C) 2015 Elsevier B.V. All rights reserved. KW - Acer KW - Regeneration KW - Latitudinal gradient KW - Temperature KW - Precipitation KW - Competition Y1 - 2015 U6 - https://doi.org/10.1016/j.foreco.2015.01.003 SN - 0378-1127 SN - 1872-7042 VL - 342 SP - 21 EP - 29 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Grimshwa, Jane T1 - Last resorts and grammaticality JF - Linguistics in Potsdam N2 - A “last resort” is argued to be nothing more than a winning, i.e. grammatical form, once it is understood in terms of competition between alternative candidates. It is a theorem of OT that we find last resort effects, since it follows from the nature of competition and constraint interaction. KW - Economy KW - Optimality Theory KW - Competition Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-32302 SN - 1616-7392 SN - 1864-1857 IS - 25 SP - 33 EP - 41 ER - TY - JOUR A1 - Kastius, Alexander A1 - Schlosser, Rainer T1 - Dynamic pricing under competition using reinforcement learning JF - Journal of revenue and pricing management N2 - Dynamic pricing is considered a possibility to gain an advantage over competitors in modern online markets. The past advancements in Reinforcement Learning (RL) provided more capable algorithms that can be used to solve pricing problems. In this paper, we study the performance of Deep Q-Networks (DQN) and Soft Actor Critic (SAC) in different market models. We consider tractable duopoly settings, where optimal solutions derived by dynamic programming techniques can be used for verification, as well as oligopoly settings, which are usually intractable due to the curse of dimensionality. We find that both algorithms provide reasonable results, while SAC performs better than DQN. Moreover, we show that under certain conditions, RL algorithms can be forced into collusion by their competitors without direct communication. KW - Dynamic pricing KW - Competition KW - Reinforcement learning KW - E-commerce KW - Price collusion Y1 - 2021 U6 - https://doi.org/10.1057/s41272-021-00285-3 SN - 1476-6930 SN - 1477-657X VL - 21 IS - 1 SP - 50 EP - 63 PB - Springer Nature Switzerland AG CY - Cham ER - TY - JOUR A1 - Leifso, A. A1 - MacDougall, A. S. A1 - Husband, B. A1 - Hierro, J. L. A1 - Köchy, Martin A1 - Pärtel, M. A1 - Peltzer, D. A. T1 - Expansion of a globally pervasive grass occurs without substantial trait differences between home and away populations JF - Oecologia N2 - The global expansion of species beyond their ancestral ranges can derive from mechanisms that are trait-based (e.g., post-establishment evolved differences compared to home populations) or circumstantial (e.g., propagule pressure, with no trait-based differences). These mechanisms can be difficult to distinguish following establishment, but each makes unique predictions regarding trait similarity between ancestral ('home') and introduced ('away') populations. Here, we tested for trait-based population differences across four continents for the globally distributed grass Dactylis glomerata, to assess the possible role of trait evolution in its worldwide expansion. We used a common-environment glasshouse experiment to quantify trait differences among home and away populations, and the potential relevance of these differences for competitive interactions. Few significant trait differences were found among continents, suggesting minimal change during global expansion. All populations were polyploids, with similar foliar carbon:nitrogen ratios (a proxy for defense), chlorophyll content, and biomass. Emergence time and growth rate favored home populations, resulting in their competitive superiority over away populations. Small but significant trait differences among away populations suggest different introductory histories or local adaptive responses following establishment. In summary, the worldwide distribution of this species appears to have arisen from its pre-adapted traits promoting growth, and its repeated introduction with cultivation and intense propagule pressure. Global expansion can thus occur without substantial shifts in growth, reproduction, or defense. Rather than focusing strictly on the invader, invasion success may also derive from the traits found (or lacking) in the recipient community and from environmental context including human disturbance. KW - Invasion ecology KW - Common-environment trial KW - Competition KW - Plant functional traits KW - Orchard grass Y1 - 2012 U6 - https://doi.org/10.1007/s00442-012-2370-4 SN - 0029-8549 VL - 170 IS - 4 SP - 1123 EP - 1132 PB - Springer CY - New York ER - TY - JOUR A1 - Nottebrock, Henning A1 - Esler, Karen J. A1 - Schurr, Frank Martin T1 - Effects of intraspecific and community density on the lifetime fecundity of long-lived shrubs JF - Perspectives in plant ecology, evolution and systematics N2 - Intra- and interspecific density dependence has profound consequences for plant population and community dynamics. In long-lived plants, however, lifetime patterns and mechanisms of density dependence are difficult to study. Here, we examine effects of intraspecific and community density on the lifetime fecundity of two long-lived shrub species from South African Fynbos: Protea repens (animal-pollinated, hermaphroditic) and Leucadendron rubrum (wind-pollinated, dioecious). Both species are serotinous, retaining seeds in cones until fire kills the mother plant. We measured lifetime fecundity as the product of cone number, proportion of cones that are not damaged by predation and seed set (fertile seeds per intact cone). Intraspecific and community densities were quantified by counting individuals of target species and all Proteaceae in small- and large-scale neighbourhoods (10 m and 50 m radius) around each focal individual. Additionally, we determined the age and size of focal individuals. We found that lifetime fecundity of the wind-pollinated L rubrum is density independent. In contrast, the lifetime fecundity of the animal-pollinated P. repens increases with large-scale intraspecific density and shows a hump-shaped relationship to large-scale community density. Community density has a hump-shaped effect on seed set (probably through partial absence of generalized pollinators at low and competition for pollinators at high densities) and negatively affects cone number per individual. For both species, plant age decreases seed set while increasing lifetime fecundity. The qualitative differences in the density dependence of lifetime fecundity may arise from differences between animal and wind pollination. In particular, interactions with generalized animal pollinators may cause community-level Allee effects with profound consequences for the future dynamics of long-lived plant populations and communities. KW - Competition KW - Community-level Allee effects KW - Facilitation KW - Fitness components KW - Interspecific interactions KW - Plant-animal interactions Y1 - 2013 U6 - https://doi.org/10.1016/j.ppees.2013.03.003 SN - 1433-8319 VL - 15 IS - 3 SP - 150 EP - 161 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Panhans, Matthew T. A1 - Schumacher, Reinhard T1 - Theory in closer contact with industrial life BT - American institutional economists on competition theory and policy JF - Journal of institutional economics N2 - This paper investigates the views on competition theory and policy of the American institutional economists during the first half of the 20th century. These perspectives contrasted with those of contemporary neoclassical and later mainstream economic approaches. We identify three distinct dimensions to an institutionalist perspective on competition. First, institutionalist approaches focused on describing industry details, so as to bring theory into closer contact with reality. Second, institutionalists emphasized that while competition was sometimes beneficial, it could also be disruptive. Third, institutionalists had a broad view of the objectives of competition policy that extended beyond effects on consumer welfare. Consequently, institutionalists advocated for a wide range of policies to enhance competition, including industrial self-regulation, broad stakeholder representation within corporations, and direct governmental regulations. Their experimental attitude implied that policy would always be evolving, and antitrust enforcement might be only one stage in the development toward a regime of industrial regulation. KW - Competition KW - economic thought KW - industrial organization KW - institutional KW - economics KW - institutionalism KW - public policy Y1 - 2021 U6 - https://doi.org/10.1017/S1744137421000357 SN - 1744-1374 SN - 1744-1382 VL - 17 IS - 5 SP - 781 EP - 798 PB - Cambridge Univ. Press CY - Cambridge ER - TY - JOUR A1 - Quintana, Xavier D. A1 - Arim, Matias A1 - Badosa, Anna A1 - Maria Blanco, Jose A1 - Boix, Dani A1 - Brucet, Sandra A1 - Compte, Jordi A1 - Egozcue, Juan J. A1 - de Eyto, Elvira A1 - Gaedke, Ursula A1 - Gascon, Stephanie A1 - Gil de Sola, Luis A1 - Irvine, Kenneth A1 - Jeppesen, Erik A1 - Lauridsen, Torben L. A1 - Lopez-Flores, Rocio A1 - Mehner, Thomas A1 - Romo, Susana A1 - Sondergaard, Martin T1 - Predation and competition effects on the size diversity of aquatic communities JF - Aquatic sciences : research across boundaries N2 - Body size has been widely recognised as a key factor determining community structure in ecosystems. We analysed size diversity patterns of phytoplankton, zooplankton and fish assemblages in 13 data sets from freshwater and marine sites with the aim to assess whether there is a general trend in the effect of predation and resource competition on body size distribution across a wide range of aquatic ecosystems. We used size diversity as a measure of the shape of size distribution. Size diversity was computed based on the Shannon-Wiener diversity expression, adapted to a continuous variable, i.e. as body size. Our results show that greater predation pressure was associated with reduced size diversity of prey at all trophic levels. In contrast, competition effects depended on the trophic level considered. At upper trophic levels (zooplankton and fish), size distributions were more diverse when potential resource availability was low, suggesting that competitive interactions for resources promote diversification of aquatic communities by size. This pattern was not found for phytoplankton size distributions where size diversity mostly increased with low zooplankton grazing and increasing nutrient availability. Relationships we found were weak, indicating that predation and competition are not the only determinants of size distribution. Our results suggest that predation pressure leads to accumulation of organisms in the less predated sizes, while resource competition tends to favour a wider size distribution. KW - Phytoplankton KW - Zooplankton KW - Fish KW - Size distribution KW - Predation KW - Competition KW - Compositional data analysis Y1 - 2015 U6 - https://doi.org/10.1007/s00027-014-0368-1 SN - 1015-1621 SN - 1420-9055 VL - 77 IS - 1 SP - 45 EP - 57 PB - Springer CY - Basel ER -