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Lowland forests in Europe went through dramatic changes in the last century. Data accumulated from the nature reserve Buky u Vysokeho Chvojna in the Czech Republic provide a unique opportunity to follow beech forest development using a time series consisting of five points in time from 1926 to 2019. Our goal was to reconstruct changes in plant species richness and plant community composition over this period. Based on the available data, we concluded that vascular plant species richness per plot declined by at least 50%, possibly by 75% since 1951. Compositional dissimilarities between the first survey and subsequent resurveys revealed a directional trajectory of vegetation changes. Treating time as an environmental factor and tree canopy cover as a covariable (and vice versa) in canonical correspondence analysis permutation tests where only the herbaceous layer was used, time turned out to be much more important. Variance partitioning revealed that time explained 28.1% and tree canopy 4.2% of the variation in the species data. The two variables together explained 36.8% of the variance, revealing that the shared effect of these two variables was 4.5%. Ellenberg-type indicator values point to a possible role of increasing nitrogen and decreasing pH. Several other factors potentially responsible for observed vegetation changes are discussed.

Aim Extinctions of species and subspecific taxa in hotspots of biodiversity deserve special attention. After more than 40 years of major efforts, estimates of extinct plant taxa in California seem to be somewhat stabilized. The time is ripe for an attempt to critically evaluate our current knowledge of plant extinctions in California and make a comparison with other countries with mediterranean-type climates. Location California. Methods Besides species-specific studies and personal communications, major databases and state floras were consulted. Results Compared with all numbers published earlier, the current analysis ended with smaller numbers of globally extinct plant species and taxa (13 and 17, respectively) and larger numbers of species and taxa extinct in California, but still present in at least one other state or country (15 and 15). For each species, life form, habitat, year of the last collection and assumed drivers of extinction are listed. Main conclusions Most of the presumed extinct taxa were originally present in one or two counties and often are known from only one or a very few collections. Therefore, the most robust generalization regarding factors contributing to taxon extinctions is a small range size and a low original abundance. Most of the presumed globally extinct taxa were originally present in lowlands where most of the human population and habitat destruction are concentrated. Taxa limited to special habitats, like wetlands, seem to be more predisposed to extinction. Among assumed drivers of plant extinction, agriculture, urbanization and development in general are the most often cited possibilities. Compared with other countries with mediterranean-type climates, the extinction rate of vascular plants in California is lower than in Israel, comparable with the Cape Province of South Africa, Western Australia and continental Mediterranean European countries, and higher than in Chile.

Author(s): Richter, C; Rejmanek, M; Miller, JED; Welch, KR; Weeks, JM; Safford, H | Abstract: The combination of direct human influences and the effects of climate change are resulting in altered ecological disturbance regimes, and this is especially the case for wildfires. Many regions that historically experienced low–moderate severity fire regimes are seeing increased area burned at high severity as a result of interactions between high fuel loads and climate warming with a number of negative ecological effects. While ecosystem impacts of altered fire regimes have been examined in the literature, little is known of the effects of changing fire regimes on forest understory plant diversity even though understory taxa comprise the vast majority of forest plant species and play vital roles in overall ecosystem function. We examined understory plant diversity across gradients of wildfire severity in eight large wildfires in yellow pine and mixed conifer temperate forests of the Sierra Nevada, California, USA. We found a generally unimodal hump-shaped relationship between local (alpha) plant diversity and fire severity. High-severity burning resulted in lower local diversity as well as some homogenization of the flora at the regional scale. Fire severity class, post-fire litter cover, and annual precipitation were the best predictors of understory species diversity. Our research suggests that increases in fire severity in systems historically characterized by low and moderate severity fire may lead to plant diversity losses. These findings indicate that global patterns of increasing fire size and severity may have important implications for biodiversity.

Identifying potentially invasive species and preventing their introduction and establishment are of critical importance in invasion ecology and land management. Although an extensive body of research has been dedicated to identifying traits that confer invasiveness, our current knowledge is still often inconclusive due to limitations in geographic extent and/or scope of traits analyzed. Here, using a comprehensive set of 45 traits, we performed a case study of invasive traits displayed by exotic woody plants in the United States (U.S.) by comparing 63 invasive and 794 non-invasive exotic woody plant species naturalized across the country. We found that invasive woody species often bear the following two key traits: vegetative reproduction and long-distance seed dispersal (via water, birds or mammals). Boosted classification tree models based on these traits accurately predicted species invasiveness (86% accuracy on average). Presented findings provide a generalized understanding of the relative importance of functional traits in identifying potentially invasive woody species in the U.S. The knowledge generated in this study can be used to improve current classification systems of non-native woody plants used by various U.S. governmental agencies and land managers.

For much of the twentieth century, many or most scholarly journals in biodiversity, ecology, biogeography and conservation were owned and published by scientific societies and made available to the broader scientific community at relatively low cost. However, the past several decades have seen a dominant process of commercialization of the publication process in this field, either by commercial publishing firms taking over publication of journals owned by a society (e.g., Evolution), or by commercial publishers starting new journals to fill “niches” that were until then empty in the scholarly publishing ecosystem. Diversity and Distributions is an example of this latter category of journals, having been created by Wiley Publishers in 1993 (as Biodiversity Letters). Being a journal owned by a commercial publisher, it has always been accessed by readers via subscription, but the publication process has been free to potential authors whose work has passed peer review.

Angola is one of the most neglected African countries in terms of botanical research, in respect of both native and naturalized species. We conducted a rapid assessment of invasive plant species in western Angola during August 2014. In thirteen primary vegetation types, we recorded populations of 44 naturalized plant species, nineteen of which are conclusively invasive (spreading far from introduction sites). Dense invasive populations of Chromolaena odorata, Inga vera and Opuntia stricta pose the greatest environmental and economic threats. Some species with known taxonomic and/or biogeographic uncertainties (e.g. Chromolaena odorata and Ageratina adenophora) or which lacked key characteristics for identification such as flowers during our survey (e.g. Eucalyptus spp.) were subjected to DNA barcoding for comparisons with available genetic data from other studies. This approach allowed us to confirm the identity of taxonomically challenging taxa such as Inga vera, Opuntia stricta and Prosopis chilensis, to conclusively differentiate Chromolaena odorata from Ageratina adenophora, and identify the subspecific identity of Acacia saligna. Canonical correspondence analysis was used to assess the presence and abundance of invasive plant species with respect to the major abiotic factors and vegetation types. Three fairly distinct groups of species emerge from this analysis: (i) species of dry lowland habitats (Calotropis gigantea, Leucaena leucocephala and Opuntia stricta); (ii) species of relatively wet habitats at mid elevations (Ageratum conyzoides, Bidens pilosa, Cardiospermum grandiflorum, Chromolaena odorata, Solanum mauritianum and Tithonia diversifolia); and (iii) upland species (Ageratina adenophora, Galinsoga parviflora and Tagetes minuta). Several invasive species that are widespread in other tropical and subtropical African countries are currently either missing (e.g. many Australian Acacia species, Azolla filiculoides, Broussonetia papyrifera, Clidemia hirta, Parthenium hysterophorus, Rubus rosaefolius, Salvinia molesta), have only very localized populations in Angola (e.g. Lantana camara, Prosopis chilensis) or exist only as planted individuals (e.g. Acacia mearnsii and A. saligna subsp. saligna).

PREMISE OF THE STUDY Revealing biological differences between invasive and noninvasive species is essential for predicting species' distribution changes with global environmental change. While most research has focused on differences between invasive and noninvasive species under favorable conditions using herbaceous species, invasive woody angiosperms are also of great ecological concern. Our study focused on how growth and allocation may change for invasive and noninvasive, mediterranean, woody angiosperms under future conditions caused by global change, specifically increased nitrogen deposition and drought. METHODS We tested how seedling functional traits differed between invasive and noninvasive woody angiosperms under different experimental conditions in a greenhouse setting. We compared growth rates and allocation patterns using two levels of soil nitrogen and three levels of watering. We also examined trait log response ratios to increases in nitrogen and increases in water. Our study sampled angiosperm trees and shrubs, incorporating congeneric/confamilial relationships through 13 phylogenetically controlled contrasts. KEY RESULTS Three functional traits were highly and positively associated with plant invasiveness for most conditions studied: seedling plant mass, leaf area, and height. Invasive species also had significantly higher root mass ratios at low water regardless of nitrogen input. Invasive and noninvasive species had similar log response ratios to increases in nitrogen and watering for studied traits. CONCLUSIONS Mediterranean, woody, invasive species' larger mass, leaf area, and early height advantage under elevated nitrogen input and increased root production in drought conditions may lead to increased invasion of these species with expected global climate change.

Broad‐scale animal diversity patterns have been traditionally explained by hypotheses focused on climate–energy and habitat heterogeneity, without considering the direct influence of vegetation structure and composition. However, integrating these factors when considering plant–animal correlates still poses a major challenge because plant communities are controlled by abiotic factors that may, at the same time, influence animal distributions. By testing whether the number and variation of plant community types in Europe explain country‐level diversity in six animal groups, we propose a conceptual framework in which vegetation diversity represents a bridge between abiotic factors and animal diversity. We show that vegetation diversity explains variation in animal richness not accounted for by altitudinal range or potential evapotranspiration, being the best predictor for butterflies, beetles, and amphibians. Moreover, the dissimilarity of plant community types explains the highest proportion of variation in animal assemblages across the studied regions, an effect that outperforms the effect of climate and their shared contribution with pure spatial variation. Our results at the country level suggest that vegetation diversity, as estimated from broad‐scale classifications of plant communities, may contribute to our understanding of animal richness and may be disentangled, at least to a degree, from climate–energy and abiotic habitat heterogeneity.

Species abilities for seed germination and seedling survival under different situations are good predictors of their capacity to colonize a broad range of habitats. Biotic conditions related to understory cover, and abiotic factors such as litter thickness and soil moisture can be determinants of plant establishment. We evaluated seed germination, seedling survival, and growth of the invasive tree Hovenia dulcis under experimental field conditions in three successional stages (open, semi-open, and closed vegetation) of a fragmented seasonal deciduous forest in southern Brazil. Our hypotheses were that H. dulcis seed germination, seedling survival, and seedling growth decrease along the successional gradient, that these factors are positively affected by soil moisture and percentage of bare soil, and negatively affected by understory cover and litter thickness. We also tested the hypothesis that herbivory on H. dulcis would decrease along the successional gradient. Our main finding was that H. dulcis can germinate and establish along all forest successional stages because it is shade-tolerant. Abiotic factors were more important than biotic factors for seed germination. Soil moisture positively affected seed germination while litter thickness negatively influenced seed germination. Percentage of bare soil negatively influenced seedling survival. Germination rates were higher in closed vegetation, whereas seedling survival was higher in semi-open vegetation, and growth rates were higher in open vegetation. There was no difference in herbivory among successional stages. The results of our study show that intermediate forest succession stages congregate the most favorable conditions for H. dulcis establishment, likely making them more susceptible to invasion.

Majority of invasive trees colonize grasslands, shrublands, and temperate forests. Hovenia dulcis is an exception, because it is one of the most pervasive invaders in Brazilian subtropical forests where it has changed their structure and composition. This study has aimed to identify the clues for its success by defining the structural and functional characteristics of plant communities in different stages of succession with and without H. dulcis. Following the general assumptions of invasion ecology, we expected that H. dulcis establishment and invasion success would be significantly higher in early successional communities, with high resource availability and low species richness and diversity, as well as low functional diversity. Contrary to this hypothesis, no differences were found between plant communities invaded and non-invaded by H. dulcis at three different succession stages. No relationship was found between species richness and diversity and functional diversity, with respect to invasibility along the successional gradient. Hovenia dulcis is strongly associated with semi-open vegetation, where the species was found in higher density. The invasion of open vegetation is more recent, providing evidence of the species’s ability to invade plant communities in early successional stages. We concluded that the colonization by H. dulcis was associated with forest openness, but the species is also able to colonize semi-open vegetation, and persist in the successionally more advanced communities.

© 2017, Springer International Publishing Switzerland. In tropical rainforests, gaps created by fallen canopy trees are the primary colonization sites for pioneer species. Selective logging mimics these natural disturbances in that only a single tree is felled, creating a gap of comparable size. Rates of tree felling greatly exceed natural mortality rates, however, changing disturbance regime by increasing the number of gaps in logged areas compared to intact forest. Little is known about whether gaps in logged forests are qualitatively different as well. At Gunung Palung National Park in West Kalimantan, Indonesia, a period of selective logging in areas adjacent to the research station created a natural experiment permitting comparison of populations of the invasive pioneer tree Bellucia pentamera in selectively logged and undisturbed forest. We sought to first establish whether canopy gaps are necessary for invasion by B. pentamera. We then examined whether the type of gap (logging vs. natural treefall) had an effect on recruitment. Finally, we compared populations in natural treefall gaps in logged and undisturbed forest to estimate the effect of logging on population size. Bellucia pentamera was limited to gaps, regardless of canopy tree density. Furthermore, gaps created by selective logging supported significantly more B. pentamera individuals than natural gaps. Finally, natural treefall gaps in the disturbed area contained significantly more individuals than gaps in the undisturbed forest. Therefore, it appears that selective logging not only created more gaps for B. pentamera, these gaps in particular promoted greater abundance of this invader and led to a population increase throughout the disturbed habitat.

Questions: How many vegetation classes and alliances are described in European countries? What are the main factors driving the number of these vegetation types? What would be the estimated number of vegetation types in so far under-explored regions outside Europe? Location: Twenty-three countries and regions in Europe. Fourteen regions outside Europe. Methods: We compiled lists of vegetation types (phytosociological classes as broader units and alliances as narrower ones) described in European countries with a well-developed vegetation classification. The delimitation and nomenclature of classes and alliances were standardized according to a unified classification system for Europe. Generalized linear models were used to test the influence of floristic richness, area, sampling effort, altitudinal range and geological diversity on the number of vegetation types. Best predictors were used to estimate the number of classes and alliances in selected regions over the world. Results: In agreement with broadly recognized diversity patterns, we found the highest numbers of vegetation types in countries with a mediterranean climate. The numbers of classes and alliances per country did not depend on the country size, while country's floristic richness was identified as the main explanatory variable, accounting for up to 67% of explained deviance. The number of alliances increased in countries with broad altitudinal range and large geological diversity, but these variables did not influence the number of classes. Accordingly, estimates of the number of alliances for other (mostly non-European) regions were adjusted when including altitudinal range as an additional predictor. Conclusions: At broad scales, the number of vegetation types can be predicted from floristic richness, which indirectly accounts for the effect of area, and from environmental heterogeneity. Furthermore, this overview demonstrates that the number of phytosociological alliances reflects biogeographic patterns in Europe better than the number of classes. We also estimate, for the first time, the number of vegetation types that may be expected in so far poorly surveyed regions worldwide, using procedures of vegetation classification analogous to those used in European phytosociology.

Scientists, managers, and policy-makers need functional and effective metrics to improve our understanding and management of biological invasions. Such metrics would help to assess progress towards management goals, increase compatibility across administrative borders, and facilitate comparisons between invasions. Here we outline key characteristics of tree invasions (status, abundance, spatial extent, and impact), discuss how each of these characteristics changes through time, and examine potential metrics to describe and monitor them. We recommend quantifying tree invasions using six metrics: (a) current status in the region; (b) potential status; (c) the number of foci requiring management; (d) area of occupancy (AOO) (i.e. compressed canopy area or net infestation); (e) extent of occurrence (EOO) (i.e. range size or gross infestation); and (f) observations of current and potential impact. For each metric we discuss how they can be parameterised (e.g. we include a practical method for classifying the current stage of invasion for trees following Blackburn?s unified framework for biological invasions); their potential management value (e.g. EOO provides an indication of the extent over which management is needed); and how they can be used in concert (e.g. combining AOO and EOO can provide insights into invasion dynamics; and we use potential status and threat together to develop a simple risk analysis tool). Based on these metrics, we propose a standardised template for reporting tree invasions that we hope will facilitate cross-species and inter-regional comparison. While we feel this represents a valuable step towards standardised reporting, there is an urgent need to develop more consistent metrics for impact and threat, and for many specific purposes additional metrics are still needed (e.g. detectability is required to assess the feasibility of eradication). Fil: Wilson, John R. U.. Kirstenbosch National Botanical Gardens; Sudáfrica. Stellenbosch University; Sudáfrica Fil: Caplat, Paul. Lund University; Suecia Fil: Dickie, Ian A.. Crown Research Institutes. Landcare Research; Nueva Zelanda. Lincoln University; Nueva Zelanda Fil: Hui, Can. Stellenbosch University; Sudáfrica Fil: Maxwell, Bruce D.. State University Of Montana; Estados Unidos Fil: Nuñez, Martin Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina Fil: Pauchard, Anibal. Universidad de Concepción; Chile Fil: Rejmanek, Marcel. University of California; Estados Unidos Fil: Richardson, David M.. Stellenbosch University; Sudáfrica Fil: Robertson, Mark P.. University of Pretoria; Sudáfrica Fil: Spear, Dian. Kirstenbosch National Botanical Gardens; Sudáfrica. Stellenbosch University; Sudáfrica Fil: Webber, Bruce L.. University of Western Australia; Australia. CSIRO Ecosystem Sciences; Australia Fil: Van Wilgen, Brian W.. Stellenbosch University; Sudáfrica Fil: Zenni, Rafael D.. University Of Tennessee; Estados Unidos

The global database of invasive trees and shrubs has been updated, resulting in a total of 751 species (434 trees and 317 shrubs) from 90 families (Rejmanek and Richardson 2013 Divers Distrib 19:1093–1094). This database is used to assess major trends in human-assisted exchanges of dendrofloras among 15 major geographical regions. Areas most invaded by non-native trees are Pacific Islands (136 species), Southern Africa (118), Australia (116), and North America (114). Areas most invaded by non-native shrubs are North America (98), Australia (87), Pacific Islands (71), and Europe (61). The most important sources of invasive trees are Asia (122–146 species, depending on how many Eurasian species are considered to have been introduced only from Europe), Australia (81), and South America (81). The most important sources of invasive shrubs are Asia (103–118), Europe (68), and South America (54). Mean number of native geographical regions for invasive trees is 1.64, while the mean number of invaded regions by trees is 2.51. The difference is smaller for shrubs: 1.60 versus 2.11. Asia is the major source of invasive Rosaceae shrubs, as well as invasive Arecaceae and Oleaceae species. South America and Australia are major sources of invasive Fabaceae trees. North America and Europe are major sources of invasive Pinaceae. Most of the invasive Salicaceae are of Eurasian origin. The identified trends will very likely continue in this century. Because of increasing interactions with many states in Asia, even more invasive woody species will be introduced from this part of the world.

Recruitment limitation of trees in tropical forests can occur because of high rates of seed predation or low rates of seed dispersal, but the degree to which limitation is influenced by variation in seed predator abundance, and hence variation in seed predation and dispersal, is not well understood. We experimentally reduced the density of a granivorous small mammal (Heteromys desmarestianus) by 90 % to assess the degree to which its rates of seed predation and dispersal limit seed to seedling survival of nine species of trees in a Neotropical lowland forest. Overall, the proportion of seeds that germinated was influenced more by high rates of predation than by limited dispersal. Reduction in density of H. desmarestianus resulted in an order of magnitude decrease in fruit removal rates and an order of magnitude increase in both the absolute and relative numbers of seeds that germinated. However, the proportion of seeds that were cached remained relatively constant across all periods and between control grids and removal plots. In removal plots, H. desmarestianus dispersed and cached about 10 % of the fruits they handled, of which approximately 25 % germinated. This was 2 to 3 times greater than the germination rates of undispersed seeds, and for two species dispersed seeds were the only ones that germinated. The results suggest the simultaneous occurrence of both seed predation and dispersal limitation for trees with animal-dispersed seeds, but there may also be a hierarchy of importance in the relative strength of these two mechanisms that is determined by the dynamics of seed predator populations.

We examined assemblages of trees and two major groups of vertebrate seed dispersers, birds and primates, in Ugandan protected areas to evaluate the roles of dispersal limitation and species sorting in community assembly. We conducted partial Mantel tests to investigate relationships between community similarity, environmental distance and geographic distance. Results showed that environmental factors, specifi cally temperature and rainfall, signifi cantly and more strongly structured tree assemblages than geographic distance. Analysis of tree dispersal modes revealed wind-dispersed tree guilds were signifi cantly dispersal limited but trees dispersed by animals were not. For assemblages of vertebrate seed dispersers, dispersal limitation signifi cantly and more strongly structured assemblages of primates than species sorting whereas environmental factors signifi cantly and more strongly structured assemblages of birds than dispersal limitation. We therefore examined whether trees dispersed by primates were more dispersal limited than trees dispersed by birds. We found consistent trends that primate fruit trees were more dispersal limited than bird fruit trees using three defi nitions of dispersal syndromes based on fruit color. Our results suggest that the dispersal abilities of primary consumers may aff ect the distribution of primary producers at large spatial scales.

The intermediate disturbance hypothesis (IDH) predicts a hump-shaped pattern between community diversity and disturbance, and is central to understanding patterns of species diversity. Here, we examine IDH in the context of alien plant invasions. IDH can offer insight into the role of disturbance in facilitating plant invasions and the effect of these invasions on floristic diversity. Early stages of succession are most susceptible to invasion because resources and colonisation opportunities are elevated after disturbance. This trend is accentuated by human-mediated dispersal, a bias towards early successional species in the alien species pool, the tendency for fast-growing species to profit most from enemy release, and increased disturbance levels in human-modified habitats. Human disturbance, coupled with plant introductions, extends the diversity–disturbance curve and shifts peak diversity towards higher disturbance levels. However, invasive aliens can reduce native diversity at the community scale, especially in mid succession where competitive interactions structure communities. Certain invasive plants may have higher impacts because they overcome some life history tradeoffs as a result of their association with humans or novel evolutionary histories, e.g. enemy release. This may directly or indirectly (e.g. through plastic reallocation of resources from defence into growth) enable invasive plants to colonise earlier or persist into later stages of succession. By modifying disturbance regimes, invaders that transform the environment may also interfere with succession and precipitate low diversity communities. Low introduction rates of late successional species may currently limit impacts of aliens under infrequent disturbance. IDH is a useful framework for understanding ecological communities. However, because of the novel evolutionary histories of alien species and the anthropogenic context in which they invade, disturbance levels that maximise total diversity in invaded communities can differ from those that maximise native diversity. Joint consideration of IDH and alien invasion patterns suggests a range of strategies can be used to manage diversity.

Previous studies on alien species establishment in the United States and around the world have drastically improved our understanding of the patterns of species naturalization, biological invasions, and underlying mechanisms. Meanwhile, relevant new data have been added and the data quality has significantly increased along with the consistency of related concepts and terminology that are being developed. Here using new and/or improved data on the native and exotic plant richness and many socioeconomic and physical variables at the state level in the United States, we attempt to test whether previously discovered patterns still hold, particularly how native and exotic species are related and what are the dominant factors controlling the plant naturalization. We found that, while the number of native species is largely controlled by natural factors such as area and temperature, exotic species and exotic fraction are predominantly influenced by social factors such as human population. When domestically introduced species were included, several aspects in earlier findings were somewhat altered and additional insights regarding the mechanisms of naturalization could be achieved. With increased data availability, however, a greater challenge ahead appears to be how many and which variables to include in analyses.

Seed disperser preferences may mediate the impact of invasive, non-native plant species on their new ecological communities. Significant seed disperser preference for invasives over native species could facilitate the spread of the invasives while impeding native plant dispersal. Such competition for dispersers could negatively impact the fitness of some native plants. Here, we review published literature to identify circumstances under which preference for non-native fruits occurs. The importance of fruit attraction is underscored by several studies demonstrating that invasive, fleshy-fruited plant species are particularly attractive to regional frugivores. A small set of studies directly compare frugivore preference for native vs. invasive species, and we find that different designs and goals within such studies frequently yield contrasting results. When similar native and non-native plant species have been compared, frugivores have tended to show preference for the non-natives. This preference appears to stem from enhanced feeding efficiency or accessibility associated with the non-native fruits. On the other hand, studies examining preference within existing suites of co-occurring species, with no attempt to maximize fruit similarity, show mixed results, with frugivores in most cases acting opportunistically or preferring native species. A simple, exploratory meta-analysis finds significant preference for native species when these studies are examined as a group. We illustrate the contrasting findings typical of these two approaches with results from two small-scale aviary experiments we conducted to determine preference by frugivorous bird species in northern California. In these case studies, native birds preferred the native fruit species as long as it was dissimilar from non-native fruits, while non-native European starlings preferred non-native fruit. However, native birds showed slight, non-significant preference for non-native fruit species when such fruits were selected for their physical resemblance to the native fruit species. Based on our review and case studies, we propose that fruit characteristics of native plant communities could dictate how well a non-native, fleshy-fruited plant species competes for dispersers with natives. Native bird preferences may be largely influenced by regional native fruits, such that birds are attracted to the colors, morphology, and infructescence structures characteristic of preferred native fruits. Non-native fruits exhibiting similar traits are likely to encounter bird communities predisposed to consume them. If those non-natives offer greater fruit abundance, energy content, or accessibility, they may outcompete native plants for dispersers.

Summary 1. Early detection of biological invasions can reduce the costs of control and increase its e!cacy. Although much research focuses on the appearance or establishment of new invaders, few studies target the detection of spread from established populations. Managers of natural areas have limited resources; therefore, there is need for e!cient methods of quantifying the spread of likely invaders inlocal and regionalareas. 2. We employed homeowner surveys, seedling outplanting, directed seedling searches and randomly located plots to determine whether two introduced species of Oleaceae, Ligustrum lucidum and Olea europaea, demonstrate invasive levels of recruitment in California’s Sacramento Valley. These methodsare examples of low-costapproaches toexamining theregional spreadof non-native woodyspecieswithdi"eringhabitat requirements. 3. Homeowner surveys indicated abundant recruitment of L. lucidum in irrigated areas, with no evident decline by distance from horticultural source trees. Ligustrum lucidum seedlings established readily when planted immediately adjacent to streams, but were unable to survive summer drought whenlocated furtherfromthe water. 4. Recruitment of O. europaea at distances >100 m from source trees was uncommon. Spread of O. europaea is rare relative to the number of reproductive individuals that have been planted in the studyarea; whereitoccurs, seedling recruitmentappearslargelya function of propagulepressure. 5. Synthesis and applications. Low-cost and rapid methods are essential for successful long-term monitoring of spread from populations of introduced, woody plant species. We employed highe!ciency methods of spread detection for two species of Oleaceae with invasive potential and existing populations in the study region. We detected no barriers to spread by L. lucidum in areas with elevated soil moisture and consider the species a likely riparian invader. By comparison, O. europaea shows little tendency to spread. We suggest that managers combine low-input methods and direct surveys towards habitats of conservation concern and routes of likely seed dispersal.

Aim Pine trees (genus Pinus) represent an ancient lineage, naturally occurring almost exclusively in the Northern Hemisphere, but introduced and widely naturalized in both hemispheres. As large trees of interest to forestry, they attract much attention and their distribution is well documented in both indigenous and naturalized ranges. This creates an opportunity to analyse the relationship between indigenous and naturalized range sizes in the context of different levels of human usage, biological traits and the characteristics of the environments of origin. Location Global. Methods We combined and expanded pre-existing data sets for pine species distributions and pine species traits, and used a variety of regression techniques (including generalized additive models and zero-inflated Poisson models) to assess which variables explained naturalized and indigenous range sizes. Results Indigenous and naturalized range sizes are positively correlated but there are many notable exceptions. Some species have large indigenous ranges but small or no naturalized ranges, whereas others have small indigenous ranges, but have naturalized in many regions. Indigenous range is correlated to factors such as seed size (−), age at first reproduction (−), and latitude (+, supporting Rapoport's rule), but also to the extent of coverage of species in the forestry literature (+). Naturalized range size is strongly influenced by the extent of coverage of species in the forestry literature (+), a proxy for propagule pressure. Naturalization was also influenced by average elevation in the indigenous range (−) and age at first reproduction (−). Main conclusions The macroecological and evolutionary pressures facing plant groups are not directly transferable between indigenous and naturalized ranges. In particular, there are strong biases in species naturalization and expansion in invasive ranges that are unrelated to factors determining indigenous range size. At least for Pinus, a new set of macroecological patterns are emerging which are profoundly influenced by humans.

Aim Woody plants were not widely considered to be important invasive alien species until fairly recently. Thousands of species of trees and shrubs have, however, been moved around the world. Many species have spread from planting sites, and some are now among the most widespread and damaging of invasive organisms. This article presents a global list of invasive alien trees and shrubs. It discusses taxonomic biases, geographical patterns, modes of dispersal, reasons for introductions and key issues regarding invasions of non-native woody plants around the world. Location Global. Methods An exhaustive survey was made of regional and national databases and the literature. Correspondence with botanists and ecologists and our own observations in many parts of the world expanded the list. Presence of invasive species was determined for each of 15 broad geographical regions. The main reasons for introduction and dissemination were determined for each species. Results The list comprises 622 species (357 trees, 265 shrubs in 29 plant orders, 78 families, 286 genera). Regions with the largest number of woody invasive alien species are: Australia (183); southern Africa (170); North America (163); Pacific Islands (147); and New Zealand (107). Species introduced for horticulture dominated the list (62% of species: 196 trees and 187 shrubs). The next most important reasons for introduction and dissemination were forestry (13%), food (10%) and agroforestry (7%). Three hundred and twenty-three species (52%) are currently known to be invasive in only one region, and another 126 (20%) occur in only two regions. Only 38 species (6%) are very widespread (invasive in six or more regions). Over 40% of invasive tree species and over 60% of invasive shrub species are bird dispersed. Main conclusions Only between 0.5% and 0.7% of the world’s tree and shrub species are currently invasive outside their natural range, but woody plant invasions are rapidly increasing in importance around the world. The objectively compiled list of invasive species presented here provides a snapshot of the current dimensions of the phenomenon and will be useful for screening new introductions for invasive potential.

Summary 1. The ornamental plant trade, forestry, and agriculture have been responsible for the initial introduction of over 60% of invasive alien plant species. Screening tools to test potentially new horticultural species should help curtail the continued introduction of new invaders. 2. Using two methods for analysing phylogenetically independent contrasts (PICs) of known invasive and non-invasive, exotic woody horticultural species, we tested the potential of relative growth rate (RGR) and related traits including net assimilation rate (NAR), leaf area ratio (LAR), and specific leaf area (SLA) as predictors of invasiveness. These 29 PICs include 65 species and broadly cover angiosperms. 3. Without accounting for phylogeny, no significant differences were found in seedling RGR or related traits between invasive and non-invasive woody species. Using PICs, invasive species’ RGRs were significantly higher. RGR was considerably more significant using our extensive dataset than in previous smaller studies, while SLA and LAR remained marginally significant. NAR was significantly higher for invasives for the 10–20 days interval. 4. Analysis of this broad data set confirms that RGR is significantly higher for invasive woody species than their non-invasive counterparts, and may serve as a useful biological predictor of invasiveness for woody angiosperms. This expanded study shows that plant species use different physiological and biomass allocation patterns to achieve higher RGR; therefore individual components of RGR, such as SLA, do not consistently predict potential invasiveness of species. 5. Synthesis and applications. Comparative seedling RGR studies show that this measure has potential as a screening tool for new exotic plant species. Unfortunately, more easily measurable components of RGR do not consistently predict invasiveness, as previously thought. Using seedling RGR analysis as an invasive species’ screening tool requires growing a species proposed for introduction with related invasive and non-invasive species. If the tested species’ RGR is higher or not significantly different from its known invasive counterpart, it should be considered highly likely to become invasive, and excluded from further consideration as a potential horticultural species. Seedling RGR could potentially produce a useful, straightforward screening tool when phylogenetically related species or cultivars are available.

Introduced species have the potential to impact processes central to the organization of ecological communities. Although hundreds of nonnative plant species have naturalized in the United States, only a small percentage of these have been studied in their new biotic communities. Their interactions with resident (native and introduced) bird species remain largely unexplored. As a group, citizen scientists such as ornithologists possess a wide range of experiences. They may offer insights into the prevalence and form of bird interactions with nonnative plants on a broad geographic scale. We surveyed 173 ornithologists from four U.S. states, asking them to report observations of bird interactions with nonnative plants. The primary goal of the survey was to obtain information useful in guiding future empirical research. In all, 1143 unique bird-plant interactions were reported, involving 99 plant taxa and 168 bird species. Forty-seven percent of reported interactions concerned potential dispersal (feeding on seeds or fruits). Remaining "habitat interactions" involved bird use of plants for nesting, perching, woodpecking, gleaning, and other activities. We utilized detrended correspondence analysis to ordinate birds with respect to the plants they reportedly utilize. Results illuminate the new guilds formed by these interactions. We assessed the existing level of knowledge about invasiveness of those plants reported most often in feeding interactions, identifying information gaps for biological invasions research priority. To exemplify the usefulness of citizen science data, we utilized survey results to guide field research on invasiveness in some of these plant species and observed both qualitatively and quantitatively strong agreement between survey reports and our empirical data. Questionnaire reports are therefore heuristically informative for the fields of both avian ecology and invasion biology.

Competitive abilities of Potamogeton pectinatus L. and Potamogeton gramineus L. were estimated using additive series experiments at across a gradient of total daily irradiance ranging from 1.2 to 9.7 mol m−2 day−1. Results for P. gramineus showed that its mean weight per plant was reduced more by the presence of other P. gramineus plants than by changes in the density of P. pectinatus. However, the difference was statistically significant only at the higher light levels examined. In the case of P. pectinatus, P. gramineus exerted a stronger impact on P. pectinatus plants than did other P. pectinatus plants. Coefficients representing interspecific competition were significantly greater than those representing intraspecific competition at higher light levels. These results indicate that P. gramineus was a stronger competitor when light levels were high. They further indicate that at low light levels, there was little evidence that competition was a strong force in determining either species performance. These results support a theory offered by Grime. However, it was possible to predict that P. gramineus would be a stronger competitor based on its light compensation point which was lower than the one for P. pectinatus. This demonstrates the utility of the R* approach proposed by Tilman. Aspects of both approaches may aid ecologists in understanding community structure.

The ecological effects of Chinese tallowtree are well documented in the southeastern United States, yet this known invasive plant continues to be planted extensively in California's Central Valley, where it has recently naturalized in several locations. Climate modeling suggests that most of California's lowland riparian habitat is susceptible to invasion by Chinese tallowtree; however, no field tests are available to corroborate this result for California or to identify local environmental constraints that might limit potential habitats. We used observational and experimental methods to evaluate invasion potential of Chinese tallowtree in riparian habitats in California's Central Valley. High invasion potential, indicated by an intersection of the maxima of dispersal probability, germination, and survivorship of seedlings, occurred at low elevations immediately next to perennial waters. The main factor limiting Chinese tallowtree invasion potential in more elevated habitats appears to be lack of seedling drought tolerance. These findings suggest that California's riparian habitats are vulnerable to invasion by Chinese tallowtree, especially downstream of current naturalized populations where water or bird dispersal will deposit seeds in environments ideal for germination and growth.

Understanding causal factors of exotic species invasions is important not only for prevention and prioritizing control efforts, but also for providing valuable insights into the underlying biology of contrasting life-history strategies. In seedling growth analyses, invasive woody species were compared with less-invasive woody species commonly cultivated in California using phylogenetically corrected procedures (12 phylogenetically independent contrasts). Invasive species were hypothesized to have higher seedling relative growth rates (RGRs) and specific leaf areas (SLAs) than did related less-invasive species. In phylogenetically independent contrasts conducted among taxa within families, high seedling RGRs and SLAs have significant positive associations with woody plant invasiveness. For contrasts containing species invasive in mediterranean regions, invasive species had significantly larger root biomass allocation than did less-invasive species. Optimization of fast seedling growth (high RGR) associated with opportunistic resource acquisition (high SLA) and increased root allocation to survive summer drought may be critical for the success of plant invaders in regions with mediterranean climates.

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 animal-mediated 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 conductive for the establishment of various alien/alien synergisms are becoming more abundant. Incorporating perspectives on mutualisms in screening protocols will improve (but not perfect) our ability to predict whether a given plant species could invade a particular habitat.

The Japanese raisin tree (Hovenia dulcis) is an invasive tree in South American forests, which produces capsuled fruits attached to peduncles that grow thick and fleshy when ripe. Frugivorous birds have been cited as dispersal agents of H. dulcis. The spread of H. dulcis propagules to non-invaded sites was evaluated at a local spatial scale in deciduous forests in Southern Brazil, in order to propose management strategies to prevent the arrival of propagules of such species in non-invaded sites. Seed arrival by birds was assessed by installing five 0.6 x 0.6 m seed traps in each 10 x 10 m plots installed in non-invaded sites at different distances from invaded sites. Seed arrival was also compared between control plots and plots where all H. dulcis trees were felled within a 30m radius from the center of plots. A limitation in short distance seed dispersal by birds was observed in the study area. There was a negative exponential relationship between number of seeds and distance from H. dulcis trees to non-invaded sites and a positive exponential dependence of the number of seeds found in seed traps on the basal area of H. dulcis. The felling of H. dulcis trees was effective in reducing the arrival of seeds in non-invaded sites, resulting in a significantly smaller number of seeds in managed plots than in control plots. A uva-do-Japão (Hovenia dulcis Thunb.) é uma espécie exótica invasora em florestas na América do Sul que produz infrutescências compostas por frutos secos aos quais estão presos pedúnculos que se tornam doces e carnosos quando maduros. Espécies de aves frugívoras são citadas como agentes dispersores de H. dulcis. A chegada de sementes de H. dulcis em sítios não-invadidos foi avaliada em escala espacial local em área de Floresta Estacional Decidual no sul do Brasil, com o intuito de propor estratégias de manejo para conter a colonização por H. dulcis nesses sítios. A chegada de sementes foi avaliada por meio de coletores de sementes instalados em sítios não-invadidos, localizados a diferentes distâncias de sítios invadidos. A chegada de sementes também foi comparada entre parcelas controle e parcelas submetidas ao corte de árvores de H. dulcis em um raio de 30 metros ao redor das mesmas. Detectou-se uma limitação na dispersão de sementes de H. dulcis por aves a curtas distâncias na área de estudo. Foi observada uma relação exponencial negativa entre o número de sementes e a distância de árvores de H. dulcis em sítios não-invadidos, enquanto uma relação exponencial positiva foi encontrada entre o número de sementes e a área basal das árvores amostradas. A eliminação de árvores de H. dulcis foi efetiva para reduzir a chegada de sementes em sítios não colonizados pela espécie, havendo um menor número de sementes em parcelas submetidas ao corte do que em parcelas controle. Fil: Dechoum, Michele. Universidade Federal de Santa Catarina; Brasil Fil: Rejmánek, Marcel. University of California at Davis; Estados Unidos Fil: Tarabini Castellani, Tania. Universidade Federal de Santa Catarina; Brasil Fil: Zalba, Sergio Martín. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Grupo de Estudios en Conservación y Manejo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

La facilitacion de la dispersion de las semillas entre plantas vecinas se puede definir como un incremento en el numero, distancia, y/o lugares alcanzados por las semillas de una planta debido a la presencia de plantas vecinas que co-fructifican y con las que la especie comparte dispersores de semillas. Se han descrito muchos casos de este fenomeno entre especies nativas y algunas tambien entre especies introducidas invasoras. Ademas, se ha informado de la facilitacion del reclutamiento de especies nativas por arboles no-nativos de fruto carnoso. Sorprendentemente, la facilitacion de la dispersion de semillas de las especies exoticas por especies nativas es menos comun, o no ha sido debidamente documentada hasta el momento. La observacion casual de la vegetacion secundaria en la Region de la Araucania, Chile, sugiere que mas individuos de la especie exotica Rubus praecox (Rosaceae), cuyos frutos carnosos son dispersados por las aves, se establecen bajo el arbol nativo Aristotelia chilensis (Elaeocarpaceae) que tambien posee frutos carnosos, que bajo otra especies de arboles nativos con frutos secos en las mismas areas. Para evaluar si las diferencias de observacion sugeridas son estadisticamente significativas, se muestrearon dos parcelas para estudiar las asociaciones interespecificas entre Rubus y Aristotelia y entre Rubus y el arbol mas comun de frutos secos -Lomatia hirsuta (Proteaceae). La primera conclusion importante de este estudio es que la invasora Rubus es mucho mas comun bajo ambas especies focales que en pastizales abiertos. En segundo lugar, Rubus se asocia mas fuertemente con Aristotelia subdioica con frutos carnosos que con la especie monoica de frutos secos Lomatia,en este paisaje del sur de Chile. Ademas, la frecuencia de Rubus es mayor bajo arboles productores de frutos de Aristotelia (femeninos o hermafroditas). Se discuten las implicaciones para la gestion de la especie invasora.

The control and/or removal of a dominant invasive species is expected to lead to increases in native species richness and diversity. Small pilot studies were performed on Santa Cruz Island (SCI), California, in the early 1990s to test the efficacy of different methods on the control of Foeniculum vulgare (fennel) and management’s effects on native species recovery. We chose a treatment that showed significant native species recovery, applied it at the landscape scale, and followed its effects on fennel infested plant communities. We tested the hypothesis that results from small-scale studies translate to the landscape level. We found that although the control of fennel translated from the small to landscape scale, decreasing from an average of 60% to less than 3% cover, native species recovery did not occur in the landscape study as it did in the pilot studies. Invasive fennel cover was replaced by non-native grass cover over time. Unexpectedly, fennel cover in untreated fennel plots decreased significantly (though not as drastically) from over 60% cover to just under 40% cover while native species richness in untreated areas increased significantly. The correlation between precipitation and changes in native and non-native species richness and abundance in this study imply that changes in species abundances were highly correlated with environmental fluctuations. The lack of a native seedbank and the accumulation of non-native grass litter likely prevented the recovery of native species in treated areas. Greater vertical complexity found in fennel communities, which increased visitation by frugivorous birds and likely increased native seed dispersal, may have been responsible for the increase in native species richness in the untreated areas. These results suggest that successful invasive species control and native species recovery experiments conducted at small scales may not translate to the landscape level, and active restoration should be an organic component of such large-scale projects.

Herbarium records have been widely used in biogeographical and ecological studies for decades. To test the adequacy of using herbarium records, we used residuals, calculated from the regression of the number of herbarium records on minimum residence time of Crotalaria species naturalized in Taiwan, as a predictor of species actual frequency and invasiveness. Number of positive localities (localities where a particular species is present), net infested area, maximum cover, as well as reproductive traits, were estimated for five exotic Crotalaria species with a similar minimum residence time. The tight correlation between residuals and the number of positive localities, as well as with maximum cover, confirms that herbarium records accurately reflect some aspects of the invasion success of the studied species. However, residuals were not a significant predictor of net infested area. Strong correlations between residuals and reproductive traits contributing to species fitness, including log(seeds/plant), flowers/inflorescence, inflorescences/plant, and flowers/plant supported the use of herbarium records in representing field distributions and invasiveness.

Data on floristic status, biological attributes, chronology and distribution of naturalized species have been shown to be a very powerful tool for discerning the patterns of plant invasions and species invasiveness. We analysed the newly compiled list of casual and naturalized plant species in Taiwan (probably the only complete data set of this kind in East Asia) and found that Taiwan is relatively lightly invaded with only 8% of the flora being casual or naturalized. Moreover, the index of casual and naturalized species per log area is also moderate, in striking contrast with many other island floras where contributions of naturalized species are much higher. Casual and naturalized species have accumulated steadily and almost linearly over the past decades. Fabaceae, Asteraceae, and Poaceae are the families with the most species. However, Amaranthaceae, Convolvulaceae, and Onagraceae have the largest ratios of casual and naturalized species to their global numbers. Ipomoea, Solanum and Crotalaria have the highest numbers of casual and naturalized species. About 60% of all genera with exotic species are new to Taiwan. Perennial herbs represent one third of the casual and naturalized flora, followed by annual herbs. About 60% of exotic species were probably introduced unintentionally onto the island; many species imported intentionally have ornamental, medicinal, or forage values. The field status of 50% of these species is unknown, but ornamentals represent noticeable proportions of naturalized species, while forage species represent a relatively larger proportion of casual species. Species introduced for medicinal purposes seem to be less invasive. Most of the casual and naturalized species of Taiwan originated from the Tropical Americas, followed by Asia and Europe.

We summarize information on naturalized and invasive conifers (class Pinopsida) worldwide (data from 40 countries, some with remote states/territories), and contrast these findings with patterns for other gymnosperms (classes Cycadopsida, Gnetopsida and Ginkgoopsida) and for woody angiosperms. Eighty conifer taxa (79 species and one hybrid; 13% of species) are known to be naturalized, and 36 species (6%) are ‘invasive’. This categorization is based on objective and conservative criteria relating to consistency of reproduction, distance of spread from founders, and degree of reliance on propagules from the founder population for persistence in areas well outside the natural range of species. Twenty-eight of the known invasive conifers belong to one family (Pinaceae) and 21 of these are in one genus (Pinus). The Cupressaceae (including Taxodiaceae) has six known invasive species (4%) in four genera, but the other four conifer families have none. There are also no known invasive species in classes Cycadopsida, Gnetopsida or Ginkgoopsida. No angiosperm family comprising predominantly trees and shrubs has proportionally as many invasive species as the Pinaceae. Besides the marked taxonomic bias in favour of Pinaceae, and Pinus in particular, invasiveness in conifers is associated with a syndrome of life-history traits: small seed mass (

This study was conducted in years 2000 to 2003 to compile a comprehensive list of naturalized species with background information, including origins, life forms, habits, usages, year of the first collection, and status. Major herbaria (TAI, HAST, TAIF, and NCKU) were visited to examine specimen records. Relevant publications and reliable websites and many other resources were also examined extensively for background information. Total 341 species in 222 genera and 60 families were documented as naturalized in Taiwan, representing 7.9% of the local flora. Besides, 25 species were considered as possibly naturalized due to insufficient evidences. A large portion (90.6%) of species reported here, were reported as “weeds” in other countries. Almost a half of the naturalized species (48.3%) were introduced from Americas.