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6 páginas.-- 50 referencia.-- This article is Free access in the https://doi.org/10.1111/1365-2745.13040 ; The quest for understanding the maintenance of species diversity has matured in recent decades under the umbrella of species coexistence theory, founded by Chesson (2000). The central conclusion of the theory is that coexistence at local scales depends on two opposing forces: average fitness differences between species, which drive the best-adapted species to exclude others, and stabilizing mechanisms, which promote diversity via niche differentiation. Recent theoretical work has focussed on how interactions between plants and other organisms influence the equalizing and stabilizing forces. However, there is a lack of empirical information. Therefore, the next fundamental step is to assess the prevalence of these mechanisms for controlling plant coexistence across a wide range of interactions and systems. To that end, this special feature presents 10 theoretical, observational, or manipulative studies illustrating 9 different biotic interactions including mutualisms (pollinators, seed dispersers, soil microbes, and arbuscular mycorrhizal fungi) and antagonisms (leaf and seed herbivores, and leaf and root pathogens). All studies share a common question: how biotic interactions regulate plant coexistence? Comparisons across studies suggest that biotic interactions modify both stabilizing and average fitness differences. In those cases where biotic interactions promote stable coexistence between plant species, both mutualistic and antagonistic interactions act more frequently as an equalizing rather than as a stabilizing mechanisms. Besides these generalities, the studies of this special issue also present novel theoretical and empirical approaches to better understand the maintenance of species diversity over a wide variety of systems, environmental conditions, and organisms. Synthesis. The studies presented here constitutes a solid base to empirically explore how mutualistic and antagonistic interactions act upon the determinants of plant species competition, and open novel paths for future research. Collectively, these advances will serve to pave the road for a better theoretical and empirical understanding of how biotic interactions control biodiversity ; We thank James Ross and Mark Rees for a swift editorial assistance. Ideas were develop edunderhe Lincx project (CGL2014‐61590‐EXP). O.G. acknowledges postdoctoral financial support provided by the European Union Horizon research and innovation program under the Marie Sklodowska‐Curie grant agreement no 661118‐BioFUNC. ; Peer reviewed

10 páginas.-- 4 figuras.-- 1 tablas.-- 50 referencias.-- Additional Supporting Information may be found online inthe supporting information tab for this article https://doi.org/10.1111/ele.12954 ; Theory argues that both soil conditions and aboveground trophic interactions have equivalent potential to limit or promote plant diversity. However, it remains unexplored how they jointly modify the niche differences stabilising species coexistence and the average fitness differences driving competitive dominance. We conducted a field study in Mediterranean annual grasslands to parameterise population models of six competing plant species. Spatially explicit floral visitor assemblages and soil salinity variation were characterised for each species. Both floral visitors and soil salinity modified species population dynamics via direct changes in seed production and indirect changes in competitive responses. Although the magnitude and sign of these changes were species‐specific, floral visitors promoted coexistence at neighbourhood scales, while soil salinity did so over larger scales by changing the superior competitors' identity. Our results show how below and aboveground interactions maintain diversity in heterogeneous landscapes through their opposing effects on the determinants of competitive outcomes. ; Fnancial support provided by the European Union Horizon2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 661118-BioFUNC. IB and OG acknowledge also financial support provided by the Spanish Ministry of Economy and Competitiveness, Explora Program (CGL2014-61590-EXP, LINCX). ; Peer reviewed

14 páginas.-- 4 figuras.-- 1 tabla.-- 100 referencias.-- Supplemental information associated with this article can be found, in the online version, at https://doi.org/10.1016/j.tree.2018.01.007 ; We propose to integrate niche and network theories into a single framework. This integration is possible through the strong parallelisms of concepts and methodologies of both theories. Feasibility and stability conditions are the key concepts that can allow the integration. How species interactions across trophic levels fulfill feasibility and stability conditions is yet to be discovered. The quest for understanding how species interactions modulate diversity has progressed by theoretical and empirical advances following niche and network theories. Yet, niche studies have been limited to describe coexistence within tropic levels despite incorporating information about multi-trophic interactions. Network approaches could address this limitation, but they have ignored the structure of species interactions within trophic levels. Here we call for the integration of niche and network theories to reach new frontiers of knowledge exploring how interactions within and across trophic levels promote species coexistence. This integration is possible due to the strong parallelisms in the historical development, ecological concepts, and associated mathematical tools of both theories. We provide a guideline to integrate this framework with observational and experimental studies. ; Comments from three anonymous reviewers greatly improve the quality of this paper, which is the result of a collaborative project funded by the Spanish Ministry of Economy and Competitiveness (LINCX, CGL2014-61590-EXP). OG acknowledges postdoctoral financial support provided by the Spanish Ministry of Economy and Competitiveness (JCI-2012-12061) and by the European Union Horizon 2020 research and innovation program under the Marie Sklodowska- Curie grant agreement No 661118-BioFUNC.SS alsoacknowledges support from MIT Research Committee Funds and the Mitsui Chair. Wefinally thank Phylopic.com and Melissa Broussard for providing silhouette images of plants and pollinators. ; Peer reviewed

11 páginas.- 4 figuras.- 2 tablas.-- 44 referencias.- Supplementary Information accompanies this paper at https://doi.org/10.1038/s41467-019-10453-0 .- Data availability Estimation of species demographic parameters and pairwise competitive coefficients for both climatic treatments are available at Dryad Digital Repository https://doi.org/10.5061/dryad.5d1s952. Average species means for the 19 functional traits included in this experiment are included in Supplementary Table 1. ; Functional traits are expected to modulate plant competitive dynamics. However, how traits and their plasticity in response to contrasting environments connect with the mechanisms determining species coexistence remains poorly understood. Here, we couple field experiments under two contrasting climatic conditions to a plant population model describing competitive dynamics between 10 annual plant species in order to evaluate how 19 functional traits, covering physiological, morphological and reproductive characteristics, are associated with species' niche and fitness differences. We find a rich diversity of univariate and multidimensional associations, which highlight the primary role of traits related to water- and light-use-efficiency for modulating the determinants of competitive outcomes. Importantly, such traits and their plasticity promote species coexistence across climatic conditions by enhancing stabilizing niche differences and by generating competitive trade-offs between species. Our study represents a significant advance showing how leading dimensions of plant function connect to the mechanisms determining the maintenance of biodiversity. ; Funding support to conduct the experiment was provided by the Spanish Ecological Terrestrial Society (AEET, Jóvenes Investigadores grant 2014/2). I.M. P.-R. and L.M. were funded by a "Ramón & Cajal" contract (RYC-2013-13937) and an "Acción 6 UJA" fellowship (EI_RNM4_2017), respectively. O.G. acknowledges postdoctoral financial support provided by the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement (No. 661118-BioFUNC). I.M.P.-R. and L.G.-A. also thank support from the MICINN projects DECAFUN (CGL2015-70123-R) and INTERCAPA (CGL-2014-56739-R). ; Peer reviewed

44 páginas.- 4 figuras.- 2 tablas.- 51 referencias.- Supplementary Information accompanies this paper at https://doi.org/10.1038/s41467-019-10453-0.- Estimation of species demographic parameters and pairwise competitive coefficients for both climatic treatments are available at Dryad Digital Repository https://doi.org/ 10.5061/dryad.5d1s952. Average species means for the 19 functional traits included in this experiment are included in Supplementary Table 1. ; Functional traits are expected to modulate plant competitive dynamics. However, how traits and their plasticity in response to contrasting environments connect with the mechanisms determining species coexistence remains poorly understood. Here, we couple field experiments under two contrasting climatic conditions to a plant population model describing competitive dynamics between 10 annual plant species in order to evaluate how 19 functional traits, covering physiological, morphological and reproductive characteristics, are associated with species¿ niche and fitness differences. We find a rich diversity of univariate and multidimensional associations, which highlight the primary role of traits related to water- and light-use-efficiency for modulating the determinants of competitive outcomes. Importantly, such traits and their plasticity promote species coexistence across climatic conditions by enhancing stabilizing niche differences and by generating competitive trade-offs between species. Our study represents a significant advance showing how leading dimensions of plant function connect to the mechanisms determining the maintenance of biodiversity. ; Funding support to conduct the experiment was provided by the Spanish Ecological Terrestrial Society (AEET, Jóvenes Investigadores grant 2014/2). I.M. P.-R. and L.M. were funded by a "Ramón & Cajal" contract (RYC-2013-13937) and an "Acción 6 UJA" fellowship (EI_RNM4_2017), respectively. O.G. acknowledges postdoctoral financial support provided by the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement (No. 661118-BioFUNC). I.M.P.-R. and L.G.-A. also thank support from the MICINN projects DECAFUN (CGL2015-70123-R) and INTERCAPA (CGL-2014-56739-R).

12 páginas.-- 3 figuras.-- 1 tabla.-- 58 referencias.-- Special Feature: Intransitive competition and species coexistence.-- Data available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.5d1s9 (Matías, Godoy, Gómez-Aparicio, & Pérez-Ramos, 2018). ; El artículo esta en libre acceso en la revista.-- free access article in this review ; Very little is known about how variation in environmental conditions alters the strength and the structure of competitive networks and what are the consequences of this for species coexistence. We performed a competition experiment with 10 annual plant species to parameterise a population model describing species' dynamics according to their vital rates and pairwise competitive coefficients. Seeds from all species were sown under two different climatic scenarios: (1) right before the first major storm of the growing season and (2) after an imposed fall drought of 2 months simulating an extreme climatic event of intense aridity. Species' demography and competitive responses were used to estimate pairwise stabilising niche differences and average fitness differences. In addition, we used tools from network theory to characterise the structure of multispecies competition from the determinants of species coexistence. Specifically, we evaluated changes in competitive dominance between species pairs, and the prevalence of intransitive competitive relationships for 120 triplets between these two climatic events. The experimental extreme event significantly reduced fitness differences between species pairs. Such an equalising mechanism promotes coexistence. However, niche differences were also reduced in such a way that the number of species pairs whose niche differences overcame their fitness differences was reduced from six to two. Contrary to our expectations, the extreme event did not increase the hierarchy of competitive dominance. Instead, and depending on the technique used, the prevalence of intransitivity remained marginally similar (17% to 22%) or significantly increased from 19.4% to 29.8%. This pattern was likely a consequence of the significant changes in competitive dominance between species pairs (26 changes out of 45; 58%). Although fitness differences were equalised and intransitive competition promoted, our model predicted a lower likelihood of coexistence under the extreme event for both species pairs and triplets, mainly because competitive interactions did not promote enough niche differences to balance the observed fitness asymmetries in our competitive networks. Synthesis. We empirically proved that an extreme climate results in communities with reduced niche and fitness differences in which species are less likely to coexist despite the increasing prevalence of intransitive competition. ; Was funded by a Juan de la Cierva grant (FPDI-2013-15867). O.G. acknowledges postdoctoral financial support provided by the Spanish Ministry for Education and Science (Juan de la Cierva, JCI-2012-12061), and by the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 661118-BioFUNC. Funding support to conduct the experiment was provided by the Spanish Ecological Terrestrial Society (AEET, Jóvenes Investigadores grant 2014/2). L.G.-A. acknowledges support from the MICINN project INTERCAPA (CGL-2014-56739-R) and European FEDER Funds. I.M.P.-R thanks the funding provided by the Ramón & Cajal Research Programme (RYC-2013-13937) and the Spanish MINECO project DECAFUN (CGL2015-70123-R). ; Peer reviewed

16 páginas.-- 5 figuras.-- 1 tablas.-- 56 referencias.-- This article belongs to the Special Issue "Ecology and Management of Invasive Species in Forest Ecosystems". ; There is growing recognition of the importance of soil fauna for modulating nutrient cycling processes such as litter decomposition. However, little is known about the drivers promoting changes in soil fauna abundance on a local scale. We explored this gap of knowledge in a mixed oak forest of Southern Spain, which is under decline due to the invasion of the exotic soil-borne pathogen Phytophthora cinnamomi . Meso-invertebrate abundance found in soil litter was estimated at the suborder level. We then explored their statistical correlations with respect to light availability, tree and litter characteristics, and P. cinnamomi abundance. Oribatida and Entomobryomporpha were the most abundant groups of Acari and Collembola, respectively. According to their trophic level, predator and detritivore abundances were positively correlated while detritivores were, in turn, positively correlated with pathogen abundance and negatively influenced by light availability and tree defoliation. These overall trends differed between groups. Among detritivores, Diplopoda preferred highly decomposed litter while Oribatida and Psocoptera preferred darker environments and Poduromorpha were selected for environments with lower tree defoliation. Our results show the predominant role of light availability in influencing litter fauna abundances at local scales and suggest that the invasive soil-borne pathogen P. cinnamomi is integrated in these complex relationships. ; O.G. acknowledges postdoctoral financial support provided by the European Union Horizon research and innovation program under the Marie Sklodowska-Curie grant agreement No 661118-BioFUNC. O. G. also thanks research support from the Spanish Ministry of Economy and Competitiveness through the IMPLANTIN project (CGL2015-65346-R). L.G.A. acknowledges support from the MICINN project INTERCAPA (CGL-2014-56739-R).