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An unresolved question of temperate forests is how pioneer tree species persist in mature forests. In order to understand the responsible mechanisms, we investigated a near‐climax mixed temperate forest dominated by Betula albosinensis in the Qinling Mountains of China. Through establishing four 50 m × 50 m plots, we examined the canopy disturbance characteristics and its effects on tree recruitments. We further test the intra‐ and interspecific effects on the recruitment of B. albosinensis. The obtained data demonstrated canopy disturbance was frequent but most small‐sized. The canopy gaps are caused mainly by adult B. albosinensis by snapping. The regeneration of coexistent tree species shows a distinct preference for gap size. B. albosinensis were clumped at the juvenile stage and small scales. B. albosinensis juveniles were positively associated with B. utilis juveniles and negatively associated with the conspecific and B. utilis large trees. In addition, B. albosinensis juveniles showed negative associations with contemporary other tree species. Our results suggested that canopy disturbance caused by canopy trees and gap partitioning among the coexistent tree species are important for the persistence of the mixed forest. As a main gapmaker, B. albosinensis appear to develop a self‐perpetuating life‐history trait and allow them to persist. This study aims to provide an insight into the mechanism responsible for the persistence of pioneer Betula albosinensis in mature temperate forests by analysis of canopy disturbance, regeneration mode, and spatial pattern. The results demonstrate that canopy disturbance caused by canopy trees and gap partitioning among the coexistent tree species are important for the persistence of B. albosinensis in the mature mixed forest. B. albosinensis appear to develop a self‐perpetuating life‐history trait and allow them to persist.

• Different phosphorus (P)-acquisition strategies may be relevant for species coexistence and plant performance in terrestrial communities on P-deficient soils. However, how interspecific P facilitation functions in natural systems is largely unknown. • We investigated the root physiological activities for P mobilization across 19 coexisting plant species in steppe vegetation, and then grew plants with various abilities to mobilize sorbed P in a microcosm in a glasshouse. • We show that P facilitation mediated by rhizosphere processes of P-mobilizing species promoted growth and increased P content of neighbors in a species-specific manner. When roots interacted with a facilitating neighbor, Cleistogenes squarrosa and Bromus inermis tended to show greater plasticity of root proliferation or rhizosheath acid phosphatase activity compared with other non-P-mobilizing species. Greater variation in these root traits was strongly correlated with increased performance in the presence of a facilitator. The results also show, for the first time, that P facilitation was an important mechanism underlying a positive complementarity effect. • Our study highlights that interspecific P-acquisition facilitation requires that facilitated neighbors exhibit a better match of root traits with a facilitating species. It provides a better understanding of species coexistence in P-limited communities.

We present strong evidence that pathogens play a critical role in structuring plant communities and maintaining plant diversity. Pathogens mediate plant species coexistence through trade-offs between competitive ability and resistance to pathogens and through pathogen specialization. Experimental tests of individual plant-pathogen interactions, tests of feedback through host-specific changes in soil communities, and field patterns and field experimentation consistently identify pathogens as important to plant species coexistence. These direct tests are supported by observations of the role of pathogens in generating the productivity gains from manipulations of plant diversity and by evidence that escape from native pathogens contributes to success of introduced plant species. Further work is necessary to test the role of pathogen dynamics in large-scale patterns of plant diversity and range limits, the robustness of coexistence to coevolutionary dynamics, the contribution of different pathogens, and the role of pathogens in plant succession.

1. A quantitative approach to species coexistence based on the invasibility criterion has led to an appreciation of coexistence mechanisms in terms of stabilizing and equalizing components, but major challenges are the need to consider general multispecies settings, interactions beyond competition, and multiple scales of space and time. Moreover, two essential concepts, species-level average fitness and scaling factors, have not had clear definitions. 2. A general approach to defining average fitnesses and scaling factors is given, along with the origin of stabilizing mechanisms as deviations from a reference model where no coexistence is possible. Illustrations are general Lotka-Volterra models, models accounting specifically for resource use and natural enemies, and models with temporal fluctuations. 3. Community averages of stabilizing mechanisms reveal overall opportunities for coexistence, and define mechanisms more precisely through their formulae. Average fitnesses adjusted for the presence of coexistence mechanisms provide a better definition of equalizing mechanisms. While these ideas apply to the components of invasion rates, permanence theory and stochastic persistence theory show how invasion rates can be used to demonstrate species coexistence in complex settings. 4. Although species coexistence has often focused on competition, detailed models of the roles of natural enemies provide a new perspective on the opportunities for coexistence in nature. The concept of apparent competition recognizes the essential symmetry between density-dependence from resource depletion and from supporting natural enemies. Natural enemy partitioning is the natural analogue of resource partitioning and has an equivalent role in promoting coexistence. Rather than reinforcing each other, however, the strength of coexistence is often intermediate between that implied by resource partitioning alone and that implied by natural enemy partitioning alone, as elucidated by recent LotkaVolterra theory. 5. Synthesis. Although there are alternative approaches for understanding coexistence in multispecies settings, ideas based on stabilizing and equalizing mechanisms continue to provide new insights. Multiple species and multiple trophic levels are naturally challenging, but the new theories of permanence and stochastic persistence support the critical role of invasion rates in species coexistence, and thus support the understanding to be derived by partitioning invasion rates into average fitness differences and stabilizing components.

The composition of communities is strongly altered by anthropogenic manipulations of biogeochemical cycles, abiotic conditions, and trophic structure in all major ecosystems. Whereas the effects of species loss on ecosystem processes have received broad attention, the consequences of altered species dominance for emergent properties of communities and ecosystems are poorly investigated. Here we propose a framework guiding our understanding of how dominance affects species interactions within communities, processes within ecosystems, and dynamics on regional scales. Dominance (or the complementary term, evenness) reflects the distribution of traits in a community, which in turn affects the strength and sign of both intraspecific and interspecific interactions. Consequently, dominance also mediates the effect of such interactions on species coexistence. We review the evidence for the fact that dominance directly affects ecosystem functions such as process rates via species identity (the dominant trait) and evenness (the frequency distribution of traits), and indirectly alters the relationship between process rates and species richness. Dominance also influences the temporal and spatial variability of aggregate community properties and compositional stability (invasibility). Finally, we propose that dominance affects regional species coexistence by altering metacommunity dynamics. Local dominance leads to high beta diversity, and rare species can persist because of source—sink dynamics, but anthropogenically induced environmental changes result in regional dominance and low beta diversity, reducing regional coexistence. Given the rapid anthropogenic alterations of dominance in many ecosystems and the strong implications of these changes, dominance should be considered explicitly in the analysis of consequences of altered biodiversity.

Accumulating evidence suggests that herbivorous insects influence the local composition and richness of Neotropical plant species, particularly in species-rich genera. Species richness, phylogenetic diversity, and chemical diversity all influence the ability of insect herbivores to find and utilize their hosts. The relative impact of these components of diversity on species coexistence and plant—herbivore interactions is not well understood. We constructed 60 local communities of up to 13 species of Piper (Piperaceae) in native, mature forest at a lowland wet forest location in Costa Rica. The species composition of each community was chosen such that species richness, phylogenetic diversity, and GCMS-based chemical diversity were varied independently among communities. We predicted that chemical diversity would most strongly affect the communities across time, with smaller effects of taxonomic and phylogenetic diversity. At 13 months after the experimental planting, we assessed survivorship of each cutting, measured total leaf area loss of the survivors, leaf area loss to generalist and specialist herbivorous insect species, and local extinction of species. Generalist and specialist herbivory decreased with increasing levels of species richness and phylogenetic diversity, respectively. Surprisingly, there was no independent effect of chemical diversity on any of the three measures of herbivore damage. Nevertheless, plots with a higher chemical and phylogenetic diversity showed decreased plant mortality and local species extinction. Overall, our results suggested that both chemical and phylogenetic similarity are important factors in the assembly andmaintenance of tropical plant communities. The fact that chemical diversity influences plant mortality suggests that leaf herbivores, and possibly other plant natural enemies, could increase plant diversity via the selective mortality of similar chemotypes.

The Janzen–Connell hypothesis proposes that specialist natural enemies, such as herbivores and pathogens, maintain diversity in plant communities by reducing survival rates of conspecific seeds and seedlings located close to reproductive adults or in areas of high conspecific density. Variation in the strength of distance‐ and density‐dependent effects is hypothesized to explain variation in plant species richness along climatic gradients, with effects predicted to be stronger in the tropics than the temperate zone and in wetter habitats compared to drier habitats. We conducted a comprehensive literature search to identify peer‐reviewed experimental studies published in the 40+ years since the hypothesis was first proposed. Using data from these studies, we conducted a meta‐analysis to assess the current weight of evidence for the distance and density predictions of the Janzen–Connell hypothesis. Overall, we found significant support for both the distance‐ and density‐dependent predictions. For all studies combined, survival rates were significantly reduced near conspecifics compared to far from conspecifics, and in areas with high densities of conspecifics compared to areas with low conspecific densities. There was no indication that these results were due to publication bias. The strength of distance and density effects varied widely among studies. Contrary to expectations, this variation was unrelated to latitude, and there was no significant effect of study region. However, we did find a trend for stronger distance and density dependence in wetter sites compared to sites with lower annual precipitation. In addition, effects were significantly stronger at the seedling stage compared to the seed stage. Synthesis. Our study provides support for the idea that distance‐ and density‐dependent mortality occurs in plant communities world‐wide. Available evidence suggests that natural enemies are frequently the cause of such patterns, consistent with the Janzen–Connell hypothesis, but additional studies are needed to rule out other mechanisms (e.g. intraspecific competition). With the widespread existence of density and distance dependence clearly established, future research should focus on assessing the degree to which these effects permit species coexistence and contribute to the maintenance of diversity in plant communities.

Microbes are thought to maintain diversity in plant communities by specializing on particular species, but it is not knownwhether microbes that specialize within species (i.e., on genotypes) affect diversity or dynamics in plant communities. Here we show that soil microbes can specialize at the within-population level in a wild plant species, and that such specialization could promote species diversity and seed dispersal in plant communities. In a shadehouse experiment in Panama, we found that seedlings of the native tree species, Virola surinamensis (Myristicaceae), had reduced performance in the soil microbial community of their maternal tree compared with in the soil microbial community of a nonmaternal tree from the same population. Performance differences were unrelated to soil nutrients or to colonization by mycorrhizal fungi, suggesting that highly specialized pathogens were the mechanism reducing seedling performance in maternal soils. We then constructed a simulation model to explore the ecological and evolutionary consequences of genotype-specific pathogens in multispecies plant communities. Model results indicated that genotype-specific pathogens promote plant species coexistence—albeit less strongly than species-specific pathogens—and are most effective at maintaining species richness when genetic diversity is relatively low. Simulations also revealed that genotype-specific pathogens select for increased seed dispersal relative to species-specific pathogens, potentially helping to create seed dispersal landscapes that allow pathogens to more effectively promote diversity. Combined, our results reveal that soil microbes can specialize within wild plant populations, affecting seedling performance near conspecific adults and influencing plant community dynamics on ecological and evolutionary time scales.

Most species have one or more natural enemies, e.g., predators, parasites, pathogens, and herbivores, among others. These species in turn typically attack multiple victim species. This leads to the possibility of indirect interactions among those victims, both positive and negative. The term apparent competition commonly denotes negative indirect interactions between victim species that arise because they share a natural enemy. This indirect interaction, which in principle can be reflected in many facets of the distribution and abundance of individual species and more broadly govern the structure of ecological communities in time and space, pervades many natural ecosystems. It also is a central theme in many applied ecological problems, including the control of agricultural pests, harvesting, the conservation of endangered species, and the dynamics of emerging diseases. At one end of the scale of life, apparent competition characterizes intriguing aspects of dynamics within individual organisms-for example, the immune system is akin in many ways to a predator that can induce negative indirect interactions among different pathogens. At intermediate scales of biological organization, the existence and strength of apparent competition depend upon many contingent details of individual behavior and life history, as well as the community and spatial context within which indirect interactions play out. At the broadest scale of macroecology and macroevolution, apparent competition may play a major, if poorly understood, role in the evolution of species' geographical ranges and adaptive radiations.

Aim: Despite the increasing pace of urbanization, little is known about how this process affects biodiversity globally. We investigate macroecological patterns of bird assemblages in urbanized areas relative to semi-natural ecosystems. Location: World-wide. Methods: We use a database of quantitative bird surveys to compare key assemblage structure parameters for plots in urbanized and semi-natural ecosystems controlling for spatial autocorrelation and survey methodology. We use the term 'urbanized' instead of 'urban' ecosystems as many of the plots were not located in the centre of towns but in remnant habitat patches within conurbations. Results: Some macroecological relationships were conserved in urbanized landscapes. Species-area, species-abundance and species-biomass relationships did not differ significantly between urbanized and non-urbanized environments. However, there were differences in the relationships between productivity and assemblage structure. In forests, species richness increased with productivity; in both forests and open habitats, the evenness of species abundances declined as productivity increased. Among urbanized plots, instead, both species richness and the evenness of species abundances were independent of variation in productivity. Main conclusions: Remnant habitats within urbanized areas are subject to many ecological alterations, yet key macroecological patterns differ remarkably little in urbanized versus non-urbanized plots. Our results support the need for increased conservation activities in urbanized landscapes, particularly given the additional benefits of local experiences of biodiversity for the human population. With increasing urbanization world-wide, broad-scale efforts are needed to understand and manage the effects of this driver of change on biodiversity.