Many introduced plant species rely on mutualisms in their new habitats to overcome barriers to establishment and to become naturalized and, in some cases, invasive. Mutualisms involving animalmediated pollination and seed dispersal, and symbioses between plant roots and microbiota often facilitate invasions. The spread of many alien plants, particularly woody ones, depends on pollinator mutualisms. Most alien plants are well served by generalist pollinators (insects and birds), and pollinator limitation does not appear to be a major barrier for the spread of introduced plants (special conditions relating to Ficus and orchids are described). Seeds of many of the most notorious plant invaders are dispersed by animals, mainly birds and mammals. Our review supports the view that tightly coevolved, plant-vertebrate seed dispersal systems are extremely rare. Vertebrate-dispersed plants are generally not limited reproductively by the lack of dispersers. Most mycorrhizal plants form associations with arbuscular mycorrhizal fungi which, because of their low specificity, do not seem to play a major role in facilitating or hindering plant invasions (except possibly on remote islands such as the Galapagos which are poor in arbuscular mycorrhizal fungi). The lack of symbionts has, however, been a major barrier for many ectomycorrhizal plants, notably for Pinus spp. in parts of the southern hemisphere. The roles of nitrogen-fixing associations between legumes and rhizobia and between actinorhizal plants and Frankia spp. in promoting or hindering invasions have been virtually ignored in the invasions literature. Symbionts required to induce nitrogen fixation in many plants are extremely widespread, but intentional introductions of symbionts have altered the invasibility of many, if not most, systems. Some of the world's worst invasive alien species only invaded after the introduction of symbionts. Mutualisms in the new environment sometimes re-unite the same species that form partnerships in the native range of the plant. Very often, however, different species are involved, emphasizing the diffuse nature of many (most) mutualisms. Mutualisms in new habitats usually duplicate functions or strategies that exist in the natural range of the plant. Occasionally, mutualisms forge totally novel combinations, with profound implications for the behaviour of the introduced plant in the new environment (examples are seed dispersal mutualisms involving wind-dispersed pines and cockatoos in Australia ; and mycorrhizal associations involving plant roots and fungi). Many ecosystems are becoming more susceptible to invasion by introduced plants because : (a) they contain an increasing array of potential mutualistic partners (e.g. generalist frugivores and pollinators, mycorrhizal fungi with wide host ranges, rhizobia strains with infectivity across genera) ; and (b) conditions conducive for the establishment of various alien\alien synergisms are becoming more abundant. Incorporating perspectives on mutualisms in screening protocols wi...

Many introduced plant species rely on mutualisms in their new habitats to overcome barriers to establishment and to become naturalized and, in some cases, invasive. Mutualisms involving animalmediated pollination and seed dispersal, and symbioses between plant roots and microbiota often facilitate invasions. The spread of many alien plants, particularly woody ones, depends on pollinator mutualisms. Most alien plants are well served by generalist pollinators (insects and birds), and pollinator limitation does not appear to be a major barrier for the spread of introduced plants (special conditions relating to Ficus and orchids are described). Seeds of many of the most notorious plant invaders are dispersed by animals, mainly birds and mammals. Our review supports the view that tightly coevolved, plant-vertebrate seed dispersal systems are extremely rare. Vertebrate-dispersed plants are generally not limited reproductively by the lack of dispersers. Most mycorrhizal plants form associations with arbuscular mycorrhizal fungi which, because of their low specificity, do not seem to play a major role in facilitating or hindering plant invasions (except possibly on remote islands such as the Galapagos which are poor in arbuscular mycorrhizal fungi). The lack of symbionts has, however, been a major barrier for many ectomycorrhizal plants, notably for Pinus spp. in parts of the southern hemisphere. The roles of nitrogen-fixing associations between legumes and rhizobia and between actinorhizal plants and Frankia spp. in promoting or hindering invasions have been virtually ignored in the invasions literature. Symbionts required to induce nitrogen fixation in many plants are extremely widespread, but intentional introductions of symbionts have altered the invasibility of many, if not most, systems. Some of the world's worst invasive alien species only invaded after the introduction of symbionts. Mutualisms in the new environment sometimes re-unite the same species that form partnerships in the native range of the plant. Very often, however, different species are involved, emphasizing the diffuse nature of many (most) mutualisms. Mutualisms in new habitats usually duplicate functions or strategies that exist in the natural range of the plant. Occasionally, mutualisms forge totally novel combinations, with profound implications for the behaviour of the introduced plant in the new environment (examples are seed dispersal mutualisms involving wind-dispersed pines and cockatoos in Australia ; and mycorrhizal associations involving plant roots and fungi). Many ecosystems are becoming more susceptible to invasion by introduced plants because : (a) they contain an increasing array of potential mutualistic partners (e.g. generalist frugivores and pollinators, mycorrhizal fungi with wide host ranges, rhizobia strains with infectivity across genera) ; and (b) conditions conducive for the establishment of various alien\alien synergisms are becoming more abundant. Incorporating perspectives on mutualisms in screening protocols will improv...

Many ecosystems have been transformed, or degraded by human use, and restoration offers an opportunity to recover services and benefits, not to mention intrinsic values. We assessed whether restoration scientists and practitioners use their projects to demonstrate the benefits restoration can provide in their peer-reviewed publications. We evaluated a sample of the academic literature to determine whether links are made explicit between ecological restoration, society, and public policy related to natural capital. We analyzed 1,582 peer-reviewed papers dealing with ecological restoration published between 1 January 2000 and 30 September 2008 in 13 leading scientific journals. As selection criterion, we considered papers that contained either "restoration" or "rehabilitation" in their title, abstract, or keywords. Furthermore, as one-third of the papers were published in Restoration Ecology, we used that journal as a reference for comparison with all the other journals. We readily acknowledge that aquatic ecosystems are under-represented, and that the largely inaccessible gray literature was ignored. Within these constraints, we found clear evidence that restoration practitioners are failing to signal links between ecological restoration, society, and policy, and are underselling the evidence of benefits of restoration as a worthwhile investment for society. We discuss this assertion and illustrate it with samples of our findings-with regards to (1) the geographical and institutional affiliations of authors; (2) the choice of ecosystems studied, methods employed, monitoring schemes applied, and the spatial scale of studies; and (3) weak links to payments for ecosystem service setups, agriculture, and ramifications for public policy.

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Summary Savanna ecosystems show codominance of trees and grasses, and the mechanisms involved in their coexistence remain unresolved. We investigated the possible influence of small‐scale heterogeneities and disturbances in determining tree spacing and tree‐grass coexistence in semi‐arid savannas, using a spatially explicit, grid‐based simulation model. We added factors such as seed clumping, locally improved moisture conditions, vegetation clearing and combinations of all three of these variables to a previously published model. We also examined the influence of changing the size and spatiotemporal correlation among individual heterogeneities. Increased seed availability in localized clumps, especially in combination with the other heterogeneity types, had the strongest impact on the long‐term tree‐grass coexistence in the model. Localized deposition of tree seeds in herbivore dung and underground seed caches built by seed‐collecting rodents may act as a determinant of the distribution of trees in savannas. Spatially autocorrelated small‐scale heterogeneities led to a more stable coexistence of trees and grasses than uncorrelated heterogeneities did, and at high levels of autocorrelation runs with all three variables led to long‐term coexistence in up to 60% of the rainfall scenarios tested. The size of individual heterogeneities, also played a significant role in determining whether trees would establish as lone individuals or in clumps. In simulations that included small‐scale heterogeneities, the number of isolated trees scattered throughout the landscape increased, whereas large heterogeneity patches and high spatiotemporal autocorrelation tended to promote tree clustering. Simulations based on rainfall data from the southern Kalahari produced a realistic density and spatial distribution for trees in this semi‐arid savanna for a realistic range of small‐scale heterogeneities. Small‐scale disturbances and heterogeneities, at least those that furnish better establishment conditions for tree seedlings, therefore act to increase the range of environmental conditions under which trees and grasses can coexist as savanna.