TY - JOUR A1 - Socher, Stephanie A. A1 - Prati, Daniel A1 - Boch, Steffen A1 - Müller, Jörg A1 - Klaus, Valentin H. A1 - Hölzel, Norbert A1 - Fischer, Markus T1 - Direct and productivity-mediated indirect effects of fertilization, mowing and grazing on grassland species richness JF - The journal of ecology N2 - Recent declines in biodiversity have given new urgency to questions about the relationship between land-use change, biodiversity and ecosystem processes. Despite the existence of a large body of research on the effects of land use on species richness, it is unclear whether the effects of land use on species richness are principally direct or indirect, mediated by concomitant changes in ecosystem processes. Therefore, we compared the direct effects of land use (fertilization, mowing and grazing) on species richness with indirect ones (mediated via grassland productivity) for grasslands in central Europe. We measured the richness and above-ground biomass in 150 grassland plots in 3 regions of Germany (the so-called Biodiversity Exploratories). We used univariate and structural equation models to examine direct and indirect land-use effects. The direct effects of mowing (-0.37, effect size) and grazing (0.04) intensity on species richness were stronger compared with the indirect effects of mowing (-0.04) and grazing (-0.01). However, the strong negative effect of fertilization (-0.23) on species richness was mainly indirect, mediated by increased productivity compared with the weak direct negative effect (-0.07). Differences between regions in land-use effects showed five times weaker negative effects of mowing (-0.13) in the region with organic soils (Schorfheide-Chorin), strong overall negative effects of grazing (-0.29) for the region with organic soils opposed to a similar strong positive effect (0.30) in the Hainich-Dun region, whereas the Schwabische Alb region displayed a five times weaker positive effect (0.06) only. Further, fertilization effects on species richness were positive (0.03) for the region with organic soils compared to up to 25 times stronger negative effects in the other two regions. Synthesis. Our results clearly show the importance of studying both direct and indirect effects of land-use intensity. They demonstrate the indirect nature, via productivity, of the negative effect of fertilization intensity on plant species richness in the real-world context of management-induced gradients of intensity of fertilization, mowing and grazing. Finally, they highlight that careful consideration of regional environments is necessary before attempting to generalize land-use effects on species diversity. KW - biodiversity KW - determinants of plant community diversity and structure KW - ecosystem functioning KW - functional plant group KW - land use KW - productivity KW - species richness KW - structural equation modelling Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-2745.2012.02020.x SN - 0022-0477 VL - 100 IS - 6 SP - 1391 EP - 1399 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Warren, Ben H. A1 - Simberloff, Daniel A1 - Ricklefs, Robert E. A1 - Aguilee, Robin A1 - Condamine, Fabien L. A1 - Gravel, Dominique A1 - Morlon, Helene A1 - Mouquet, Nicolas A1 - Rosindell, James A1 - Casquet, Juliane A1 - Conti, Elena A1 - Cornuault, Josselin A1 - Maria Fernandez-Palacios, Jose A1 - Hengl, Tomislav A1 - Norder, Sietze J. A1 - Rijsdijk, Kenneth F. A1 - Sanmartin, Isabel A1 - Strasberg, Dominique A1 - Triantis, Kostas A. A1 - Valente, Luis M. A1 - Whittaker, Robert J. A1 - Gillespie, Rosemary G. A1 - Emerson, Brent C. A1 - Thebaud, Christophe T1 - Islands as model systems in ecology and evolution: prospects fifty years after MacArthur-Wilson JF - Ecology letters N2 - The study of islands as model systems has played an important role in the development of evolutionary and ecological theory. The 50th anniversary of MacArthur and Wilson's (December 1963) article, An equilibrium theory of insular zoogeography', was a recent milestone for this theme. Since 1963, island systems have provided new insights into the formation of ecological communities. Here, building on such developments, we highlight prospects for research on islands to improve our understanding of the ecology and evolution of communities in general. Throughout, we emphasise how attributes of islands combine to provide unusual research opportunities, the implications of which stretch far beyond islands. Molecular tools and increasing data acquisition now permit re-assessment of some fundamental issues that interested MacArthur and Wilson. These include the formation of ecological networks, species abundance distributions, and the contribution of evolution to community assembly. We also extend our prospects to other fields of ecology and evolution - understanding ecosystem functioning, speciation and diversification - frequently employing assets of oceanic islands in inferring the geographic area within which evolution has occurred, and potential barriers to gene flow. Although island-based theory is continually being enriched, incorporating non-equilibrium dynamics is identified as a major challenge for the future. KW - Community assembly KW - diversification KW - ecosystem functioning KW - genomics KW - island biogeography KW - islands as model systems KW - speciation Y1 - 2015 U6 - https://doi.org/10.1111/ele.12398 SN - 1461-023X SN - 1461-0248 VL - 18 IS - 2 SP - 200 EP - 217 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Velzen, Ellen van A1 - Gaedke, Ursula A1 - Klauschies, Toni T1 - Quantifying the capacity for contemporary trait changes to drive intermittent predator-prey cycles JF - Ecological monographs : a publication of the Ecological Society of America N2 - A large and growing body of theory has demonstrated how the presence of trait variation in prey or predator populations may affect the amplitude and phase of predator-prey cycles. Less attention has been given to so-called intermittent cycles, in which predator-prey oscillations recurrently disappear and re-appear, despite such dynamics being observed in empirical systems and modeling studies. A comprehensive understanding of the conditions under which trait changes may drive intermittent predator-prey dynamics, as well as their potential ecological implications, is therefore missing. Here we provide a first systematic analysis of the eco-evolutionary conditions that may give rise to intermittent predator-prey cycles, investigating 16 models that incorporate different types of trait variation within prey, predators, or both. Our results show that intermittent dynamics often arise through predator-prey coevolution, but only very rarely when only one trophic level can adapt. Additionally, the frequency of intermittent cycles depends on the source of trait variation (genetic variation or phenotypic plasticity) and the genetic architecture (Mendelian or quantitative traits), with intermittency occurring most commonly through Mendelian evolution, and very rarely through phenotypic plasticity. Further analysis identified three necessary conditions for when trait variation can drive intermittent cycles. First, the intrinsic stability of the predator-prey system must depend on the traits of prey, predators, or both. Second, there must be a mechanism causing the recurrent alternation between stable and unstable states, leading to a "trait" cycle superimposed on the population dynamics. Finally, these trait dynamics must be significantly slower than the predator-prey cycles. We show how these conditions explain all the abovementioned patterns. We further show an important unexpected consequence of these necessary conditions: they are most easily met when intraspecific trait variation is at high risk of being lost. As trait diversity is positively associated with ecosystem functioning, this can have potentially severe negative consequences. This novel result highlights the importance of identifying and understanding intermittent cycles in theoretical studies and natural systems. The new approach for detecting and quantifying intermittency we develop here will be instrumental in enabling future study. KW - eco-evolutionary feedbacks KW - ecosystem functioning KW - intraspecific trait KW - variation KW - population cycles KW - predator-prey dynamics KW - trait dynamics Y1 - 2022 U6 - https://doi.org/10.1002/ecm.1505 SN - 1557-7015 SN - 0012-9615 VL - 92 IS - 2 PB - Wiley CY - New York ER - TY - JOUR A1 - Marquart, Arnim A1 - Goldbach, Lars A1 - Blaum, Niels T1 - Soil-texture affects the influence of termite macropores on soil water infiltration in a semi-arid savanna JF - Ecohydrology : ecosystems, land and water process interactions, ecohydrogeomorphology N2 - Subterranean termites create tunnels (macropores) for foraging that can influence water infiltration and may lead to preferential flow to deeper soil layers. This is particularly important in water limited ecosystems such as semi-arid, agriculturally utilized savannas, which are particularly prone to land degradation and shrub-encroachment. Using termite activity has been suggested as a restoration measure, but their impact on hydrology is neither universal nor yet fully understood. Here, we used highly replicated, small-scale (50 x 50 cm) rain-simulation experiments to analyse the interacting effects of either vegetation (grass dominated vs. shrub dominated sites) or soil texture (sand vs. loamy sand) and termite foraging macropores on infiltration patterns. We used Brilliant Blue FCF as colour tracer to make the flow pathways in paired experiments visible, on either termite-disturbed soil or controls without surface macropores in two semi-arid Namibian savannas (with either heterogeneous soil texture or shrub cover). On highly shrub-encroached plots in the savanna site with heterogeneous soil texture, termite macropores increased maximum infiltration depth and total amount of infiltrated water on loamy sand, but not on sandy soil. In the sandy savanna with heterogeneous shrub cover, neither termite activity nor shrub density affected the infiltration. Termite's effect on infiltration depends on the soil's hydraulic conductivity and occurs mostly under ponded conditions, intercepting run-off. In semi-arid savanna soils with a considerable fraction of fine particles, termites are likely an important factor for soil water dynamics. KW - ecosystem functioning KW - infiltration KW - macropores KW - rain-simulation KW - shrub-encroachment KW - soil texture KW - termites Y1 - 2020 U6 - https://doi.org/10.1002/eco.2249 SN - 1936-0584 SN - 1936-0592 VL - 13 IS - 8 PB - Wiley CY - Chichester ER - TY - JOUR A1 - Venail, Patrick A1 - Gross, Kevin A1 - Oakley, Todd H. A1 - Narwani, Anita A1 - Allan, Eric A1 - Flombaum, Pedro A1 - Isbell, Forest A1 - Joshi, Jasmin Radha A1 - Reich, Peter B. A1 - Tilman, David A1 - van Ruijven, Jasper A1 - Cardinale, Bradley J. T1 - Species richness, but not phylogenetic diversity, influences community biomass production and temporal stability in a re-examination of 16 grassland biodiversity studies JF - Functional ecology : an official journal of the British Ecological Society N2 - Hundreds of experiments have now manipulated species richness (SR) of various groups of organisms and examined how this aspect of biological diversity influences ecosystem functioning. Ecologists have recently expanded this field to look at whether phylogenetic diversity (PD) among species, often quantified as the sum of branch lengths on a molecular phylogeny leading to all species in a community, also predicts ecological function. Some have hypothesized that phylogenetic divergence should be a superior predictor of ecological function than SR because evolutionary relatedness represents the degree of ecological and functional differentiation among species. But studies to date have provided mixed support for this hypothesis. Here, we reanalyse data from 16 experiments that have manipulated plant SR in grassland ecosystems and examined the impact on above-ground biomass production over multiple time points. Using a new molecular phylogeny of the plant species used in these experiments, we quantified how the PD of plants impacts average community biomass production as well as the stability of community biomass production through time. Using four complementary analyses, we show that, after statistically controlling for variation in SR, PD (the sum of branches in a molecular phylogenetic tree connecting all species in a community) is neither related to mean community biomass nor to the temporal stability of biomass. These results run counter to past claims. However, after controlling for SR, PD was positively related to variation in community biomass over time due to an increase in the variances of individual species, but this relationship was not strong enough to influence community stability. In contrast to the non-significant relationships between PD, biomass and stability, our analyses show that SR per se tends to increase the mean biomass production of plant communities, after controlling for PD. The relationship between SR and temporal variation in community biomass was either positive, non-significant or negative depending on which analysis was used. However, the increases in community biomass with SR, independently of PD, always led to increased stability. These results suggest that PD is no better as a predictor of ecosystem functioning than SR.Synthesis. Our study on grasslands offers a cautionary tale when trying to relate PD to ecosystem functioning suggesting that there may be ecologically important trait and functional variation among species that is not explained by phylogenetic relatedness. Our results fail to support the hypothesis that the conservation of evolutionarily distinct species would be more effective than the conservation of SR as a way to maintain productive and stable communities under changing environmental conditions. KW - biodiversity KW - community biomass KW - data synthesis KW - ecosystem functioning KW - grasslands KW - phylogenetic diversity KW - relatedness KW - stability Y1 - 2015 U6 - https://doi.org/10.1111/1365-2435.12432 SN - 0269-8463 SN - 1365-2435 VL - 29 IS - 5 SP - 615 EP - 626 PB - Wiley-Blackwell CY - Hoboken ER -