Contrasting patterns of naturalized plant richness in the Americas: Numbers are higher in the North but expected to rise sharply in the South

With increasing availability of plant distribution data, the information about global plant diversity is improving rapidly. Recently, Ulloa Ulloa et al. (2017) presented the first comprehensive overview of the native vascular flora of the Americas, yielding a total count of 124,993 native species. Of these, 51,241 occur in North America and 82,052 in South America. By combining these data with the information in the Global Naturalized Alien Flora (GloNAF) database of naturalized alien floras, we point out that for a complete picture of the regional and continental plant richness, the naturalized alien species need to be considered. Ignoring this novel component of regional floras can lead to an inaccurate picture of overall change in biodiversity in the Anthropocene. We show that North and South America might face contrasting challenges in terms of potential threats to biodiversity posed by alien plant species, because of the different past and present dynamics of invasions and predictions of future development. In total, there are 7,042 naturalized alien plants occurring in the Americas, with 6,122 recorded in North America and 2,677 in South America; if only introductions from other continents are considered additions to the native continental flora make up 6.9 and 1.4 %, respectively. Nevertheless, predictions of naturalized plant trajectories based on global trade dynamics and climate change suggest that considerable increases in naturalized plant numbers are expected in the next 20 years for emerging South American economies, which could reverse the present state.     

Patterns of plant invasions in China: Taxonomic,biogeographic, climatic approaches and anthropogenic effects

This study was aimed to determine the patterns as well as the effects of biological, anthropogenic, and climatic factors on plant invasions in China. About 270 volumes of national and regional floras were employed to compile a naturalized flora of China. Habit, life form, origin, distribution, and uses of naturalized plants were also analyzed to determine patterns on invasion. Correlations between biological, anthropogenic and climatic parameters were estimated at province and regional scales. Naturalized species represent 1% of the flora of China. Asteraceae, Fabaceae, and Poaceae are the dominant families, but Euphorbiaceae and Cactaceae have the largest ratios of naturalized species to their global numbers. Oenothera, Euphorbia, and Crotalaria were the dominant genera. Around 50% of exotic species were introduced intentionally for medicinal purposes. Most of the naturalized species originated in tropical America, followed by Asia and Europe. Number of naturalized species was significantly correlated to the number of native species/log area. The intensity of plant invasion showed a pattern along climate zones from mesic to xeric, declining with decreasing temperature and precipitation across the nation. Anthropogenic factor, such as distance of transportation, was significantly correlated to plant invasions at a regional scale. Although anthropogenic factors were largely responsible for creating opportunities for exotic species to spread and establish, the local biodiversity and climate factors were the major factors shaping the pattern of plant invasions in China. The warm regions, which are the hot spots of local biodiversity, and relatively developed areas of China, furthermore, require immediate attentions.     

Risk Assessment and Invasion Characteristics of Alien Plants in and Around the Agro-Pastoral Ecotone of Northern China

Two risk assessment protocols were adopted to assess the risks posed by alien plants that naturalized or non-naturalized in the agro-pastoral ecotone of northern China (AGENC). In this study the Risk Assessment for Central Europe method revealed that more than two-thirds of the 19 naturalized and four-fifths of the 17 non-naturalized alien plants presented high or moderate risk, and all 36 alien plants were considered to be rejected for their potential agricultural and environmental risks under the Australian Weed Risk Assessment system. On the characteristics of plant invasions, more attention should be given to disturbed habitats rather than these relative natural or closed ecosystems, and also be prudent and careful of the alien plants that are introduced as useful plants from North or South America and unintentional introduction from Europe. Moreover, annuals needed special attention: three-quarters of the alien plants were annual species, only a few were biennial (8.3%), perennial (11.1%), liana and tree plants (2.8%). Plant invasions are not extremely serious in the AGENC, but there are several alien plants that have naturalized and spread themselves in the region. However, attention should be given in the future to predicting and preventing plant invasions in this fragile region.     

Plant introduction,naturalization, and invasion in French Guiana (South America)

Continental tropical ecosystems are generally viewed as less vulnerable to biological invasions than island ones. Their apparent resistance to invasive alien species is often attributed to their higher native biota diversity and complexity. However, with the increase of human activities and disturbances and the accelerate rate of introductions of plant species, these apparently resilient continental ecosystems are now experiencing alien plant naturalization and invasion events. In order to illustrate this emergent phenomenon, we compiled a list of all known introduced and naturalized plant species in French Guiana (Guiana Shield, South America). A total of 490 alien plants were recorded, about 34% of which are currently naturalized, mainly species belonging to the Acanthaceae and Fabaceae (Faboideae) in the Eudicotyledons, and Poaceae (grasses) and Arecaceae (palms) in the Monocotyledons. The coastal dry and wet savannas appears to be vulnerable to plant invasion (with 165 naturalized species, about 34% of the alien flora), especially by Acacia mangium (Mimosaceae) and Melaleuca quinquenervia (Myrtaceae) which are forming localized but dense monotypic stands. Both tree species, intentionnally introduced for reforestation, rehabilitation, and as garden ornamentals and have the potential to spread with increasing human disturbances The number and abundance of naturalized alien plants in the relatively undisturbed tropical lowland rainforests and savannas remains still very low. Therefore, surveillance, early detection, and eradication of potential plant invaders are crucial; moreover collaboration with neighbouring countries of the Guiana Shield is essential to prevent the introduction of potentially invasive species which are still not present in French Guiana.     

Traits explain invasion of alien plants into tropical rainforests

• 1. The establishment of new botanic gardens in tropical regions highlights a need for weed risk assessment tools suitable for tropical ecosystems. The relevance of plant traits for invasion into tropical rainforests has not been well studied.
• 2. Working in and around four botanic gardens in Indonesia where 590 alien species have been planted, we estimated the effect of four plant traits, plus time since species introduction, on: (a) the naturalization probability and (b) abundance (density) of naturalized species in adjacent native tropical rainforests; and (c) the distance that naturalized alien plants have spread from the botanic gardens.
• 3. We found that specific leaf area (SLA) strongly differentiated 23 naturalized from 78 non‐naturalized alien species (randomly selected from 577 non‐naturalized species) in our study. These trends may indicate that aliens with high SLA, which had a higher probability of naturalization, benefit from at least two factors when establishing in tropical forests: high growth rates and occupation of forest gaps. Naturalized aliens had high SLA and tended to be short. However, plant height was not significantly related to species'' naturalization probability when considered alongside other traits.
• 4. Alien species that were present in the gardens for over 30 years and those with small seeds also had higher probabilities of becoming naturalized, indicating that garden plants can invade the understorey of closed canopy tropical rainforests, especially when invading species are shade tolerant and have sufficient time to establish.
• 5. On average, alien species that were not animal dispersed spread 78 m further into the forests and were more likely to naturalize than animal‐dispersed species. We did not detect relationships between the measured traits and estimated density of naturalized aliens in the adjacent forests.
• 6. Synthesis: Traits were able to differentiate alien species from botanic gardens that naturalized in native forest from those that did not; this is promising for developing trait‐based risk assessment in the tropics. To limit the risk of invasion and spread into adjacent native forests, we suggest tropical botanic gardens avoid planting alien species with fast carbon capture strategies and those that are shade tolerant.

     

Influence of different landscape design styles on plant invasions in Central Europe

When considering the most frequent invasive exotic plants on an international scale, it is evident that the majority are ornamentals and that they were deliberately introduced in relation to landscape design. Although there are worldwide numerous lists of invasive exotic plants—which means plants that have harmful effects on native biodiversity—an assessment of the contribution of different landscape design styles on plant invasions has not been done. We used the extensive database on the history of introduction and naturalization of alien plants into natural habitats of Central Europe (Lohmeyer and Sukopp, Agriophyten in der Vegetation Mitteleuropas in: Schriftenreihe Vegetationskunde 25, 1992; Nachtrag: Braunschweiger Geobotan Arbeiten 8:179–220, 2001) to examine how many alien ornamental plants there are in the different natural habitats; and how many of them are invasive exotic plants and—in contrast—how many have not spread significantly. Also, we researched contributions by different landscape design styles to these plant invasions since medieval times. Of the estimated 12,000 alien plant species introduced into Central Europe since the Neolithic period, 279 taxa (2.3 %) are currently identified as being naturalized in natural habitats; 103 (0.86 %) of these naturalized taxa are ornamentals, and of these, 40 (0.33 %) are invasive exotic plants. Our investigation has shown a correlation between the frequency of plant invasions and changes in landscape-design styles. Evaluating the impact of plant invasions through horticulture and landscape design on native biodiversity, our study illustrates that it is significantly lower in Central Europe than in other parts of the world.     

Simulating plant invasion dynamics in mountain ecosystems under global change scenarios

Across the globe, invasive alien species cause severe environmental changes, altering species composition and ecosystem functions. So far, mountain areas have mostly been spared from large‐scale invasions. However, climate change, land‐use abandonment, the development of tourism and the increasing ornamental trade will weaken the barriers to invasions in these systems. Understanding how alien species will react and how native communities will influence their success is thus of prime importance in a management perspective. Here, we used a spatially and temporally explicit simulation model to forecast invasion risks in a protected mountain area in the French Alps under future conditions. We combined scenarios of climate change, land‐use abandonment and tourism‐linked increases in propagule pressure to test if the spread of alien species in the region will increase in the future. We modelled already naturalized alien species and new ornamental plants, accounting for interactions among global change components, and also competition with the native vegetation. Our results show that propagule pressure and climate change will interact to increase overall species richness of both naturalized aliens and new ornamentals, as well as their upper elevational limits and regional range‐sizes. Under climate change, woody aliens are predicted to more than double in range‐size and herbaceous species to occupy up to 20% of the park area. In contrast, land‐use abandonment will open new invasion opportunities for woody aliens, but decrease invasion probability for naturalized and ornamental alien herbs as a consequence of colonization by native trees. This emphasizes the importance of interactions with the native vegetation either for facilitating or potentially for curbing invasions. Overall, our work highlights an additional and previously underestimated threat for the fragile mountain flora of the Alps already facing climate changes, land‐use transformations and overexploitation by tourism.     

Little evidence of invasion by alien conifers in Europe

Aim Conifers are invasive species in many parts of the world, especially in the Southern Hemisphere. There are many introduced conifers in Europe, but their status as alien species is poorly documented. We conducted a comprehensive literature review to ascertain the extent to which alien conifers can be considered invasive. Location Europe. Methods We reviewed the historical record of alien conifer invasion in Europe (i.e. species with a native range outside the continental boundaries of Europe) by screening the DAISIE database and the ISI Web of Science. Results According to DAISIE, there are 54 alien conifer species in Europe. Pseudotsuga menziesii is the species recorded as naturalized in the most countries (12) and the UK is the country with the most naturalized species (18). Thirty‐seven of these conifers have been studied, to some extent, in a total of 131 papers (212 records). Nevertheless, only a few papers have investigated aspects related to biological invasions. In fact, the species are not referred to as alien by the authors in more than half of the papers (66%). Twenty‐five per cent of the papers have investigated plant traits, 46% are about biotic and abiotic factors influencing tree performance and 29% deal with ecological and economic impacts. Most papers are related to entomology, dealing with natural enemies affecting the alien conifers. Main conclusions Scientists have not yet perceived alien conifers in Europe as problematic species. Moreover, the low introduction effort, long lag‐time since plantation and phylogenetic closeness between alien and native conifers are possible reasons for their low expansion in Europe to date. From a management point of view, careful observations of sites with alien conifers is necessary to watch for new invasions. From a scientific perspective, thorough analyses of the extent that introduction, rates of naturalization and biogeographical differences influence invasive spread between the two hemispheres will prove timely.     

Effects of climate change and horticultural use on the spread of naturalized alien garden plants in Europe

Climate warming is supposed to enlarge the area climatically suitable to the naturalization of alien garden plants in temperate regions. However, the effects of a changing climate on the spread of naturalized ornamentals have not been evaluated by spatially and temporarily explicit range modelling at larger scales so far. Here, we assess how climate change and the frequency of cultivation interactively determine the spread of 15 ornamental plants over the 21st century in Europe. We coupled species distribution modelling with simulations of demography and dispersal to predict range dynamics of these species in annual steps across a 250 × 250 m raster of the study area. Models were run under four scenarios of climate warming and six levels of cultivation intensity. Cultivation frequency was implemented as size of the area used for planting a species. Although the area climatically suitable to the 15 species increases, on average, the area predicted to be occupied by them in 2090 shrinks under two of the three climate change scenarios. This contradiction obviously arises from dispersal limitations that were pronounced although we assumed that cultivation is spatially adapting to the changing climate. Cultivation frequency had a much stronger effect on species spread than climate change, and this effect was non‐linear. The area occupied increased sharply from low to moderate levels of cultivation intensity, but levelled off afterwards. Our simulations suggest that climate warming will not necessarily foster the spread of alien garden plants in Europe over the next decades. However, climatically suitable areas do increase and hence an invasion debt is likely accumulating. Restricting cultivation of species can be effective in preventing species spread, irrespective of how the climate develops. However, for being successful, they depend on high levels of compliance to keep propagule pressure at a low level.     

Contrasting patterns in the invasions of European terrestrial and freshwater habitats by alien plants,insects and vertebrates

Aim To provide the first comparative overview on the current numbers of alien species that invade representative European terrestrial and freshwater habitats for a range of taxonomic groups. Location Europe. Methods Numbers of naturalized alien species of plants, insects, herptiles, birds and mammals occurring in 10 habitats defined according to the European Nature Information System (EUNIS) were obtained from 115 regional data sets. Only species introduced after ad 1500 were considered. Data were analysed by ANCOVA and regression trees to assess whether differences exist among taxonomic groups in terms of their habitat affinity, and whether the pattern of occurrence of alien species in European habitats interacts with macroecological factors such as insularity, latitude or area. Results The highest numbers of alien plant and insect species were found in human‐made, urban or cultivated habitats; if controlled for habitat area in the region, wetland and riparian habitats appeared to support relatively high numbers of alien plant species too. Invasions by vertebrates were more evenly distributed among habitats, with aquatic and riparian, woodland and cultivated land most invaded. Mires, bogs and fens, grassland, heathland and scrub were generally less invaded. Habitat and taxonomic group explained most variation in the proportions of alien species occurring in individual habitats related to the total number of alien species in a region, and the basic pattern determined by these factors was fine‐tuned by geographical variables, namely by the mainland–island contrast and latitude, and differed among taxonomic groups. Main conclusions There are two ecologically distinct groups of alien species (plants and insects versus vertebrates) with strikingly different habitat affinities. Invasions by these two contrasting groups are complementary in terms of habitat use, which makes an overall assessment of habitat invasions in Europe possible. Since numbers of naturalized species in habitats are correlated among taxa within these two groups, the data collected for one group of vertebrates, for example, could be used to estimate the habitat‐specific numbers of alien species for other vertebrate groups with reasonable precision, and the same holds true for insects and plants.     

不受欢迎的生物多样性：香港的外来植物物种

香港早在19世纪中叶开始就有外来植物入侵的记录,迄今为止,已发现多达238种已归化的外来或怀疑为外来的植物,其中又以薇甘菊（Mikania micrantha)、五爪金龙（Ipomoea cairica)、假臭草（Eupatorium catarium)、大黍（Panicum maximum)等最常见,外来植物最常见于受人为干扰的生境,例如荒废农田及路旁等,而较少在天然林地生境及贫瘠的灌草丛中发现,外来植物的对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少了生境及贫瘠的灌草丛中发现,外来植物对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少少了生境及动植物的多样性,外来动物对香港原生植物影响最大的是于20世纪70年代入侵的松树线虫（Bur-saphelenchus xylophilus)。外来的脊椎动物也有可能对香港的植物被演替产生影响,目前香港的外来植物当中,有些在大陆较少分布或没有记录,作为华南最大的港口,香港对外来物种的引入扮演着重要的角色,因此制定控制外来种在香港及华南地区的引入及传播的政策及措施非常重要。     

Upper-montane plant invasions in the Hawaiian Islands: Patterns and opportunities

In the Hawaiian Islands, massive volcanoes have created extreme elevation gradients, resulting in environments ranging from nearly tropical to alpine, spread across a distance of only a few dozen kilometers. Although the Hawaiian Islands are widely recognized for opportunities to study lowland tropical forest invasions, less attention has been paid to invasions of Hawaii's upper-montane forest, sub-alpine and alpine environments. This study synthesizes current knowledge of plant naturalization in upper-montane environments of the Hawaiian Islands in order to (1) determine whether patterns of tropical versus temperate species invasion change with elevation, and (2) evaluate whether upper-montane invaders are having significant impacts on native plant communities. A total of 151 naturalized plant species have been recorded at 2000 m or higher. Most species (93%) are herbaceous, and over half (52%) are native to Europe/Eurasia. Twenty-one species (14%) are reported to be disruptive in native plant communities, mainly by forming dense stands that appear to inhibit recruitment of natives, but also by altering vegetation structure or causing changes in ecosystem processes. Fourteen species (9%) were first recorded within the past 30 years, indicating that new invasions of upper-montane habitats are ongoing. At 1200 m elevation, only 38% of naturalized species are temperate in origin, but the proportion of temperate species increases linearly with elevation up to 3000 m (alpine habitat), where all naturalized species are temperate in origin and over 80% are native to Europe/Eurasia. Declining temperature along the elevation gradient probably drives this pattern. The extreme elevation gradients in the Hawaiian Islands provide specific opportunities for comparative studies on the ecology and evolution of temperate invaders while also creating a unique field environment for understanding interactions between temperate and tropical species.     

Naturalization of introduced plants: ecological drivers of biogeographical patterns

CONTENTS: Summary 383 I. Introduction 383 II. The introduction-naturalization-invasion continuum for conceptualizing biological invasions 384 III. The biogeographical background for studying naturalization: variation among populations and regions 385 IV. Factors determining naturalization in plants 388 Acknowledgements 392 References 392 SUMMARY: The literature on biological invasions is biased in favour of invasive species - those that spread and often reach high abundance following introduction by humans. It is, however, also important to understand previous stages in the introduction-naturalization-invasion continuum ('the continuum'), especially the factors that mediate naturalization. The emphasis on invasiveness is partly because most invasions are only recognized once species occupy large adventive ranges or start to spread. Also, many studies lump all alien species, and fail to separate introduced, naturalized and invasive populations and species. These biases impede our ability to elucidate the full suite of drivers of invasion and to predict invasion dynamics, because different factors mediate progression along different sections of the continuum. A better understanding of the determinants of naturalization is important because all naturalized species are potential invaders. Processes leading to naturalization act differently in different regions and global biogeographical patterns of plant invasions result from the interaction of population-biological, macroecological and human-induced factors. We explore what is known about how determinants of naturalization in plants interact at various scales, and how their importance varies along the continuum. Research that is explicitly linked to particular stages of the continuum can generate new information that is appropriate for improving the management of biological invasions if, for example, potentially invasive species are identified before they exert an impact.     

The biogeography of naturalization in alien plants

Aim  This paper reviews the main geographical determinants of naturalization in plants.
Location  Global.
Methods  Comparative studies of large data sets of alien floras are the main source of information on global patterns of naturalization.
Results  Temperate mainland regions are more invaded than tropical mainland regions but there seems to be no difference in invasibility of temperate and tropical islands. Islands are more invaded than the mainland. The number of naturalized species in temperate regions decreases with latitude and their geographical ranges increase with latitude. The number of naturalized species on islands increases with temperature. Naturalized species contribute to floristic homogenization, but the phenomenon is scale-dependent.
Main conclusions  Some robust patterns are evident from currently available data, but further research is needed on several aspects to advance our understanding of the biogeography of naturalization of alien plants. For example, measures of propagule pressure are needed to determine the invasibility of communities/ecosystems/regions. The patterns discussed in this paper are derived largely from numbers and proportions of naturalized species, and little is known about the proportion of introduced species that become naturalized. Further insights on naturalization rates, i.e. the proportion of aliens that successfully naturalize within regions, and on geographical and other determinants of its variation would provide us with better understanding of the invasion process. Comparative studies, and resulting generalizations, are almost exclusively based on numbers of species, but alien species differ in their impact on native biodiversity and ecosystem processes.     

Alien plant species favoured over congeneric natives under experimental climate warming in temperate Belgian climate

Climate warming and biological invasions by alien species are two key factors threatening the world’s biodiversity. To date, their impact has largely been studied independently, and knowledge on whether climate warming will promote invasions relies strongly on bioclimatic models. We therefore set up a study to experimentally compare responses to warming in native and alien plant species. Ten congeneric species pairs were exposed to ambient and elevated temperature (+3°C) in sunlit, climate-controlled chambers, under optimal water and nutrient supply to avoid interaction with other factors. All species pairs combined, total plant biomass reacted differently to warming in alien versus native species, which could be traced to significantly different root responses. On average, native species became less productive in the warmer climate, whereas their alien counterparts showed no response. The three alien species with the strongest warming response (Lathyrus latifolius, Cerastium tomentosum and Artemisia verlotiorum) are currently non-invasive but all originate from regions with a warmer climate. Still, other alien species that also originate from warmer regions became less or remained equally productive. Structural or ecophysiological acclimation to warming was largely absent, both in native and alien species, apart from light-saturated photosynthetic rate, where warming tended to restrain the native but not the alien species. A difference in the capacity to acclimate photosynthetic rates to the new climate may therefore have caused the contrasting biomass response. Future experiments are needed to ascertain whether climate warming can effectively tip the balance between native and alien competitors.     

Naturalization of ornamental plant species in public green spaces and private gardens

Ornamental horticulture is the most important pathway for alien plant introductions worldwide, and consequently, invasive spread of introduced plants often begins in urban areas. Although most introduced ornamental garden-plant species are locally not naturalized yet, many of them have shown invasion potential elsewhere in the world, and might naturalize when climate changes. We inventoried the planted flora of 50 public and 61 private gardens in Radolfzell, a small city in southern Germany, to investigate whether local naturalization success of garden plants is associated with their current planting frequency, climatic suitability (as assessed with climatic niche modelling) and known naturalization status somewhere in the world. We identified 954 introduced garden-plant species, of which 48 are already naturalized in Radolfzell and 120 in other parts of Germany. All currently naturalized garden plants in Radolfzell have a climatic suitability probability of ≥ 0.75 and are naturalized in ≥ 13 out of 843 regions globally. These values are significantly higher than those of garden plants that have not become locally naturalized yet. Current planting frequencies, however, were not related to current naturalization success. Using the identified local naturalization thresholds of climatic suitability and global naturalization frequency, and climate projections for the years 2050 and 2070, we identified 45 garden-plant species that are currently not naturalized in Radolfzell but are likely to become so in the future. Although our approach cannot replace a full risk assessment, it is well-suited and applicable as one element of a screening or horizon scanning-type approach.     

Do climatically similar regions contain similar alien floras? A comparison between the mediterranean areas of central Chile and California

Aim Taxonomic comparisons of alien floras across climatically similar regions have been proposed as a powerful approach for increasing our understanding of plant invasions across scales. However, detailed comparisons between the alien biotas of climatically similar regions are scarce. This study aims to compare the taxonomic patterns of alien species richness in mediterranean‐type climate areas of central Chile and California, in order to better understand how climatically similar regions converge or diverge in terms of their alien flora. Location Central Chile and California, United States. Methods We compared the alien floras of the state of California in the United States and central Chile, considering within‐region variation and taxonomic composition up to the species level. To test for within‐region variation, administrative units and counties were grouped within seven latitudinal bands for each region. We tested for differences in the relative contributions of the various origins of the naturalized species to each region. We used a family naturalization index to establish which families had relatively higher numbers of naturalized species in each region. We evaluated the similarity, using cluster analyses with Jaccard’s similarity index, of alien taxa between regions and latitudinal bands using presence–absence matrices at the species, genus and family levels. We used principal components analysis to determine the presence of a compositional gradient including all latitudinal bands. Results We recorded 1212 alien plant species in California and 593 in central Chile, of which 491 are shared between the two regions. These figures include 25 species that are native to California and 37 that are native to Chile. A comparison between the alien floras of central Chile and California reveals three major trends: (1) higher naturalized species diversity for California than for Chile, at all taxonomic levels; (2) differences in the proportion of species according to origin, with America, Africa, Asia and Australia providing a larger number of species in California than in Chile; (3) segregation between regions in terms of taxonomic composition of their alien flora, and a rather weak differentiation within regions; and (4) a trend towards higher similarity between the alien floras of latitudinal bands associated with higher levels of human disturbances. Main conclusions The alien floras of central Chile and California are significantly different, but this difference diminishes in highly disturbed areas. Thus, the current high levels of species movement caused by globalization, together with increasing levels of anthropogenic disturbances, should reduce the differentiation of the alien floras in these regions, increasing overall biotic homogenization.     

Arbuscular mycorrhizal status of some Kashmir Himalayan alien invasive plants

In view of the recently reported role of arbuscular mycorrhizas (AM) in plant invasions, we examined 63 alien plant species representing 26 families, collected from diverse habitat types in the Kashmir Himalaya, India, for the extent and type of their AM association. Based on the percent AM fungal root length colonization (% RLC), the investigated plants were categorized into five classes (class A = 0–5% RLC, class B = 6–25%, class C = 26–50%, class D = 51–75%, and class E = 76–100%). The number of species belonging to each of these classes was 7, 6, 22, 19, and 9, respectively. The AM colonization in 33 plant species was of Arum-type, 18 species was of Paris-type, and eight species harbored an intermediate type. Such baseline information on a large number of alien plants inhabiting diverse habitats in different biogeographical regions is needed for elucidating the role of AM fungi in alien plant invasions.     

华南地区外来入侵和归化植物分析

为了解华南地区外来植物现状,通过野外调查和查阅文献等,确定华南地区有外来入侵和归化植物45科141属223种,以菊科(Asteraceae,38种)、豆科(Fabaceae,36种)、禾本科(Poaceae,19种)植物为主,其中草本植物和原产美洲的植物占优势,分别有204种(占总数的91.5%)和163种(占73.1%)。广东外来入侵植物有159种,归化植物23种;广西有入侵植物135种,归化植物16种;海南有入侵植物111种,归化种15种;香港有入侵植物105种,归化植物9种;澳门有入侵植物89种,归化种4种;华南5省区共有的外来入侵和归化植物为57种(55种为入侵植物,2种为归化植物)。广东是外来植物种类最多的地区,与其他4省区共有的外来入侵和归化植物种类也最多,说明广东同时是外来植物输入和输出大省。由于气候和生态生境的相似性,各省区都面临着其他植物从周边地区入侵的风险,因此在治理入侵植物时,应建立联合防控机制对外来入侵植物的联合监测和防控,以提升外来入侵植物的治理成效和降低其对人类健康和生态安全的威胁。     

Do invasive alien plants benefit more from global environmental change than native plants?

Invasive alien plant species threaten native biodiversity, disrupt ecosystem functions and can cause large economic damage. Plant invasions have been predicted to further increase under ongoing global environmental change. Numerous case studies have compared the performance of invasive and native plant species in response to global environmental change components (i.e. changes in mean levels of precipitation, temperature, atmospheric CO₂ concentration or nitrogen deposition). Individually, these studies usually involve low numbers of species and therefore the results cannot be generalized. Therefore, we performed a phylogenetically controlled meta‐analysis to assess whether there is a general pattern of differences in invasive and native plant performance under each component of global environmental change. We compiled a database of studies that reported performance measures for 74 invasive alien plant species and 117 native plant species in response to one of the above‐mentioned global environmental change components. We found that elevated temperature and CO₂ enrichment increased the performance of invasive alien plants more strongly than was the case for native plants. Invasive alien plants tended to also have a slightly stronger positive response to increased N deposition and increased precipitation than native plants, but these differences were not significant (N deposition: P = 0.051; increased precipitation: P = 0.679). Invasive alien plants tended to have a slightly stronger negative response to decreased precipitation than native plants, although this difference was also not significant (P = 0.060). So while drought could potentially reduce plant invasion, increases in the four other components of global environmental change considered, particularly global warming and atmospheric CO₂ enrichment, may further increase the spread of invasive plants in the future.