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 - TY - JOUR A1 - Massie, Thomas Michael A1 - Weithoff, Guntram A1 - Kucklaender, Nina A1 - Gaedke, Ursula A1 - Blasius, Bernd T1 - Enhanced Moran effect by spatial variation in environmental autocorrelation JF - Nature Communications N2 - Spatial correlations in environmental stochasticity can synchronize populations over wide areas, a phenomenon known as the Moran effect. The Moran effect has been confirmed in field, laboratory and theoretical investigations. Little is known, however, about the Moran effect in a common ecological case, when environmental variation is temporally autocorrelated and this autocorrelation varies spatially. Here we perform chemostat experiments to investigate the temporal response of independent phytoplankton populations to autocorrelated stochastic forcing. In contrast to naive expectation, two populations without direct coupling can be more strongly correlated than their environmental forcing (enhanced Moran effect), if the stochastic variations differ in their autocorrelation. Our experimental findings are in agreement with numerical simulations and analytical calculations. The enhanced Moran effect is robust to changes in population dynamics, noise spectra and different measures of correlation-suggesting that noise-induced synchrony may play a larger role for population dynamics than previously thought. Y1 - 2015 U6 - https://doi.org/10.1038/ncomms6993 SN - 2041-1723 VL - 6 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Weithoff, Guntram A1 - Rocha, Marcia R. A1 - Gaedke, Ursula T1 - Comparing seasonal dynamics of functional and taxonomic diversity reveals the driving forces underlying phytoplankton community structure JF - Freshwater biology N2 - In most biodiversity studies, taxonomic diversity is the measure for the multiplicity of species and is often considered to represent functional diversity. However, trends in taxonomic diversity and functional diversity may differ, for example, when many functionally similar but taxonomically different species co-occur in a community. The differences between these diversity measures are of particular interest in diversity research for understanding diversity patterns and their underlying mechanisms. We analysed a temporally highly resolved 20-year time series of lake phytoplankton to determine whether taxonomic diversity and functional diversity exhibit similar or contrasting seasonal patterns. We also calculated the functional mean of the community in n-dimensional trait space for each sampling day to gain further insights into the seasonal dynamics of the functional properties of the community. We found an overall weak positive relationship between taxonomic diversity and functional diversity with a distinct seasonal pattern. The two diversity measures showed synchronous behaviour from early spring to mid-summer and a more complex and diverging relationship from autumn to late winter. The functional mean of the community exhibited a recurrent annual pattern with the most prominent changes before and after the clear-water phase. From late autumn to winter, the functional mean of the community and functional diversity were relatively constant while taxonomic diversity declined, suggesting competitive exclusion during this period. A further decline in taxonomic diversity concomitant with increasing functional diversity in late winter to early spring is seen as a result of niche diversification together with competitive exclusion. Under these conditions, several different sets of traits are suitable to thrive, but within one set of functional traits only one, or very few, morphotypes can persist. Taxonomic diversity alone is a weak descriptor of trait diversity in phytoplankton. However, the combined analysis of taxonomic diversity and functional diversity, along with the functional mean of the community, allows for deeper insights into temporal patterns of community assembly and niche diversification. KW - algae KW - biodiversity KW - functional traits KW - seasonality KW - time series Y1 - 2015 U6 - https://doi.org/10.1111/fwb.12527 SN - 0046-5070 SN - 1365-2427 VL - 60 IS - 4 SP - 758 EP - 767 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Hilt, Sabine A1 - Wanke, Thomas A1 - Scharnweber, Inga Kristin A1 - Brauns, Mario A1 - Syvaranta, Jari A1 - Brothers, Soren M. A1 - Gaedke, Ursula A1 - Köhler, Jan A1 - Lischke, Betty A1 - Mehner, Thomas T1 - Contrasting response of two shallow eutrophic cold temperate lakes to a partial winterkill of fish JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - Food-web effects of winterkill are difficult to predict as the enhanced mortality of planktivorous fish may be counterbalanced by an even higher mortality of piscivores. We hypothesised that a winterkill in a clear and a turbid shallow lake would equalise their fish community composition, but seasonal plankton successions would differ between lakes. After a partial winterkill, we observed a reduction of fish biomass by 16 and 43% in a clear-water and a turbid small temperate lake, respectively. Fish biomass and piscivore shares (5% of fish biomass) were similar in both lakes after this winterkill, but young-of-the-year (YOY) abundances were higher in the turbid lake. Top-down control by crustaceans was only partly responsible for low phytoplankton biomass at the end of May following the winterkill in both lakes. Summer phytoplankton biomass remained low in the clear-water lake despite high abundances of YOY fish (mainly roach). In contrast, the crustacean biomass of the turbid lake was reduced in summer by a high YOY abundance (sunbleak and roach), leading to a strong increase in phytoplankton biomass. The YOY abundance of fish in shallow eutrophic lakes may thus be more important for their summer phytoplankton development after winterkill than the relative abundance of piscivores. KW - Anoxia KW - Fish KW - Regime shifts KW - Roach KW - Shallow lakes KW - Submerged macrophytes Y1 - 2015 U6 - https://doi.org/10.1007/s10750-014-2143-7 SN - 0018-8158 SN - 1573-5117 VL - 749 IS - 1 SP - 31 EP - 42 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Seifert, Linda I. A1 - Weithoff, Guntram A1 - Gaedke, Ursula A1 - Vos, Matthijs T1 - Warming-induced changes in predation, extinction and invasion in an ectotherm food web JF - Oecologia N2 - Climate change will alter the forces of predation and competition in temperate ectotherm food webs. This may increase local extinction rates, change the fate of invasions and impede species reintroductions into communities. Invasion success could be modulated by traits (e.g., defenses) and adaptations to climate. We studied how different temperatures affect the time until extinction of species, using bitrophic and tritrophic planktonic food webs to evaluate the relative importance of predatory overexploitation and competitive exclusion, at 15 and 25 A degrees C. In addition, we tested how inclusion of a subtropical as opposed to a temperate strain in this model food web affects times until extinction. Further, we studied the invasion success of the temperate rotifer Brachionus calyciflorus into the planktonic food web at 15 and 25 A degrees C on five consecutive introduction dates, during which the relative forces of predation and competition differed. A higher temperature dramatically shortened times until extinction of all herbivore species due to carnivorous overexploitation in tritrophic systems. Surprisingly, warming did not increase rates of competitive exclusion among the tested herbivore species in bitrophic communities. Including a subtropical herbivore strain reduced top-down control by the carnivore at high temperature. Invasion attempts of temperate B. calyciflorus into the food web always succeeded at 15 A degrees C, but consistently failed at 25 A degrees C due to voracious overexploitation by the carnivore. Pre-induction of defenses (spines) in B. calyciflorus before the invasion attempt did not change its invasion success at the high temperature. We conclude that high temperatures may promote local extinctions in temperate ectotherms and reduce their chances of successful recovery. KW - Community dynamics KW - Freshwater ecosystem KW - Global warming KW - Species range shift KW - Trophic interactions Y1 - 2015 U6 - https://doi.org/10.1007/s00442-014-3211-4 SN - 0029-8549 SN - 1432-1939 VL - 178 IS - 2 SP - 485 EP - 496 PB - Springer CY - New York ER -