Logging,exotic plant invasions,and native plant reassembly in a lowland tropical rain forest

Habitat modification and biological invasions are key drivers of global environmental change. However, the extent and impact of exotic plant invasions in modified tropical landscapes remain poorly understood. We examined whether logging drives exotic plant invasions and whether their combined influences alter understory plant community composition in lowland rain forests in Borneo. We tested the relationship between understory communities and local‐ and landscape‐scale logging intensity, using leaf area index (LAI) and aboveground biomass (AGB) data from 192 plots across a logging‐intensity gradient from primary to repeatedly logged forests. Overall, we found relatively low levels of exotic plant invasions, despite an intensive logging history. Exotic species were more speciose, had greater cover, and more biomass in sites with more local‐scale canopy loss. Surprisingly, though, exotic species invasion was not related to either landscape‐scale canopy loss or road configuration. Moreover, logging and invasion did not seem to be acting synergistically on native plant composition, except that seedlings of the canopy‐dominant Dipterocarpaceae family were less abundant in areas with higher exotic plant biomass. Current low levels of invasion, and limited association with native understory community change, suggest there is a window of opportunity to manage invasive impacts. We caution about potential lag effects and the possibly severe negative impacts of exotic plant invasions on the long‐term quality of tropical forest, particularly where agricultural plantations function as permanent seed sources for recurrent dispersal along logging roads. We therefore urge prioritization of strategic management plans to counter the growing threat of exotic plant invasions in modified tropical landscapes.     

Global Salmonidae introductions reveal stronger ecological effects of changing intraspecific compared to interspecific diversity

The introduction of organisms within the native range of wild conspecifics is a widespread phenomenon and locally modifies patterns in intraspecific diversity. However, our knowledge of the resulting ecological effects, as opposed to those caused by invasion‐induced changes in interspecific diversity, is still limited. Here, we investigated the ecological effects of native and non‐native invaders across levels of biological organisations and recipient organisms using the global and long history introductions of salmonids. Our meta‐analysis demonstrated that the global effects of native species introductions exceeded those induced by non‐native invaders. The impacts of native invaders were primarily manifested at the individual level on wild conspecifics, but remained largely unexplored on other native organisms and at the community and ecosystem levels. Overlooked and poorly appreciated, quantifying the impacts of native invaders has important implications because human‐assisted introductions of domesticated organisms are ubiquitous and likely to proliferate in the future.     

The unseen invaders: introduced earthworms as drivers of change in plant communities in North American forests (a meta‐analysis)

Globally, biological invasions can have strong impacts on biodiversity as well as ecosystem functioning. While less conspicuous than introduced aboveground organisms, introduced belowground organisms may have similarly strong effects. Here, we synthesize for the first time the impacts of introduced earthworms on plant diversity and community composition in North American forests. We conducted a meta‐analysis using a total of 645 observations to quantify mean effect sizes of associations between introduced earthworm communities and plant diversity, cover of plant functional groups, and cover of native and non‐native plants. We found that plant diversity significantly declined with increasing richness of introduced earthworm ecological groups. While plant species richness or evenness did not change with earthworm invasion, our results indicate clear changes in plant community composition: cover of graminoids and non‐native plant species significantly increased, and cover of native plant species (of all functional groups) tended to decrease, with increasing earthworm biomass. Overall, these findings support the hypothesis that introduced earthworms facilitate particular plant species adapted to the abiotic conditions of earthworm‐invaded forests. Further, our study provides evidence that introduced earthworms are associated with declines in plant diversity in North American forests. Changing plant functional composition in these forests may have long‐lasting effects on ecosystem functioning.     

Global ecological impacts of invasive species in aquatic ecosystems

The introduction of invasive species, which often differ functionally from the components of the recipient community, generates ecological impacts that propagate along the food web. This review aims to determine how consistent the impacts of aquatic invasions are across taxa and habitats. To that end, we present a global meta‐analysis from 151 publications (733 cases), covering a wide range of invaders (primary producers, filter collectors, omnivores and predators), resident aquatic community components (macrophytes, phytoplankton, zooplankton, benthic invertebrates and fish) and habitats (rivers, lakes and estuaries). Our synthesis suggests a strong negative influence of invasive species on the abundance of aquatic communities, particularly macrophytes, zooplankton and fish. In contrast, there was no general evidence for a decrease in species diversity in invaded habitats, suggesting a time lag between rapid abundance changes and local extinctions. Invaded habitats showed increased water turbidity, nitrogen and organic matter concentration, which are related to the capacity of invaders to transform habitats and increase eutrophication. The expansion of invasive macrophytes caused the largest decrease in fish abundance, the filtering activity of filter collectors depleted planktonic communities, omnivores (including both facultative and obligate herbivores) were responsible for the greatest decline in macrophyte abundance, and benthic invertebrates were most negatively affected by the introduction of new predators. These impacts were relatively consistent across habitats and experimental approaches. Based on our results, we propose a framework of positive and negative links between invasive species at four trophic positions and the five different components of recipient communities. This framework incorporates both direct biotic interactions (predation, competition, grazing) and indirect changes to the water physicochemical conditions mediated by invaders (habitat alteration). Considering the strong trophic links that characterize aquatic ecosystems, this framework is relevant to anticipate the far‐reaching consequences of biological invasions on the structure and functionality of aquatic ecosystems.     

Evolutionary responses of natives to introduced species: what do introductions tell us about natural communities?

Biological invasions dramatically affect the distribution, abundance and reproduction of many native species. Because of these ecological effects, exotic species can also influence the evolution of natives exposed to novel interactions with invaders. Evolutionary changes in natives in response to selection from exotics are usually overlooked, yet common responses include altered anti-predator defenses, changes in the spectrum of resources and habitats used, and other adaptations that allow native populations to persist in invaded areas. Whether a native population is capable of responding evolutionarily to selection from invaders will depend on the demographic impact of the invader, the genetic architecture and genetic variability of the native population and potentially the history of previous invasions. In some cases, natives will fail to evolve or otherwise adapt, and local or global extinction will result. In other cases, adaptive change in natives may diminish impacts of invaders and potentially promote coexistence between invaders and natives. Here, we review the evidence for evolutionary responses of native species to novel community members. We also discuss how the effects of introduced species may differ from those caused by natural range expansions of native species. Notably, introduced species may come from remote biotas with no previous evolutionary history with the native community. In addition, the rate of addition of introduced species into communities is much greater than all but the most extreme cases of historical biotic exchange. Understanding the evolutionary component of exotic/native species interactions is critical to recognizing the long-term impacts of biological invasions, and to understanding the role of evolutionary processes in the assembly and dynamics of natural communities.     

Can Invasive Species Facilitate Native Species? Evidence of How, When, and Why These Impacts Occur

Although the predatory and competitive impacts of biological invasions are well documented, facilitation of native species by non-indigenous species is frequently overlooked. A search through recent ecological literature found that facilitative interactions between invasive and native species occur in a wide range of habitats, can have cascading effects across trophic levels, can re-structure communities, and can lead to evolutionary changes. These are critical findings that, until now, have been mostly absent from analyses of ecological impacts of biological invasions. Here I present evidence for several mechanisms that exemplify how exotic species can facilitate native species. These mechanisms include habitat modification, trophic subsidy, pollination, competitive release, and predatory release. Habitat modification is the most frequently documented mechanism, reflecting the drastic changes generated by the invasion of functionally novel habitat engineers. Further, I predict that facilitative impacts on native species will be most likely when invasive species provide a limiting resource, increase habitat complexity, functionally replace a native species, or ameliorate predation or competition. Finally, three types of facilitation (novel, substitutive, and indirect) define why exotic species can lead to facilitation of native species. It is evident that understanding biological invasions at the community and ecosystem levels will be more accurate if we integrate facilitative interactions into future ecological research. Since facilitative impacts of biological invasions can occur with native endangered species, and can have wide-ranging impacts, these results also have important implications for management, eradication, and restoration.Contribution Number 2293, Bodega Marine Laboratory, University of California at Davis.     

The role of species traits and taxonomic patterns in alien bird impacts

Aim To test whether the distribution of alien bird impacts varies across bird families and regions of origin, and to investigate whether species traits associated with successful introductions can predict which species will have negative impacts in the new area of introduction. Location Europe and the Mediterranean Basin. Methods Combining historical information and published literature about negative economic, biological and human health impacts, we compared the distribution of impacts among bird families and native origins of bird species for three major types of impact (economic, biodiversity and human health). We examined the relationships between ecological, biological and reproductive characteristics of species and the severity of the impacts. Results The majority of alien species with reported impacts originated from the Afrotropical, Indo‐Malayan and Palaearctic biogeographical regions. The distribution of alien bird species in Europe with reported impacts shows a taxonomic bias and largely mirrors patterns of establishment. While most species had primarily either economic or biodiversity impacts, several species in the Anatidae, Corvidae, Passeridae, Phasianidae and Sturnidae families were associated with moderate to serious negative impacts on both economic resources and native biodiversity. After controlling for taxonomic effects, species with the greatest overall impacts were habitat generalists and multi‐brooded, while species with smaller bodies and the tendency to form large feeding or roosting flocks were linked with greater impacts on native biodiversity. Main conclusions This study presents the first synthesis of published impact data for alien birds and provides a broad‐scale perspective on factors that contribute to their impacts. The results show that accounting for both species traits and taxonomy improves our ability to predict the impacts of alien bird species. Because several species are currently in the early stages of establishment in Europe, there may be an opportunity to limit negative impacts with efforts that promote proactive strategies against species and families possessing the above characteristics.     

Evaluating differences in the shape of native and alien plant trait distributions will bring new insights into invasions of plant communities

Failure to quantify differences in the shape of inter‐specific trait distributions (e.g., skew, kurtosis) when comparing co‐occurring alien and native plants hinders the integration of biological invasions and plant community ecology. Within a plant community, understanding the circumstances that lead to the shape of the inter‐specific distribution of one or more functional plant traits being unimodal, bimodal, multimodal or skewed has the potential to shed new light on community vulnerability to invasion, subsequent ecosystem impacts and the selection pressures (e.g., stabilizing, directional or disruptive) acting upon native and alien species. Ignoring differences in the shape of inter‐specific trait distributions of alien and native species could miss important insights into plant invasions, including: the existence of unsaturated native plant communities, empty niches, shifting trait optima of species as a result of environmental change and incomplete colonization–extinction processes following invasion. Future comparisons of functional trait differences between native and alien species should include assessment of the shapes of inter‐specific trait distributions since these may differ even when the mean values of traits are similar for native and alien species. The infrequent application of such approaches may explain the limited generalizations regarding the drivers and consequences of plant invasions in plant communities.     

Invasion impacts local species turnover in a successional system

Exotic plant invasions are often associated with declines in diversity within invaded communities. However, few studies have examined the local community dynamics underlying these impacts. Changes in species richness associated with plant invasions must occur through local changes in extinction and/or colonization rates within the community. We used long‐term, permanent plot data to evaluate the impacts of the exotic vine Lonicera japonica. Over time, species richness declined with increasing L. japonica cover. L. japonica reduced local colonization rates but had no effect on extinction rates. Furthermore, we detected significant reductions in the immigration of individual species as invasion severity increased, showing that some species are more susceptible to invasion than others. These findings suggest that declines in species richness associated with L. japonica invasion resulted from effects on local colonization rates only and not through the competitive displacement of established species.     

Ecological effects of non‐native species in marine ecosystems relate to co‐occurring anthropogenic pressures

Predictors for the ecological effects of non‐native species are lacking, even though such knowledge is fundamental to manage non‐native species and mitigate their impacts. Current theories suggest that the ecological effects of non‐native species may be related to other concomitant anthropogenic stressors, but this has not been tested at a global scale. We combine an exhaustive meta‐analysis of the ecological effects of marine non‐native species with human footprint proxies to determine whether the ecological changes due to non‐native species are modulated by co‐occurring anthropogenic impacts. We found that non‐native species had greater negative effects on native biodiversity where human population was high and caused reductions in individual performance where cumulative human impacts were large. On this basis we identified several marine ecoregions where non‐native species may have the greatest ecological effects, including areas in the Mediterranean Sea and along the northwest coast of the United States. In conclusion, our global assessment suggests coexisting anthropogenic impacts can intensify the ecological effects of non‐native species.     

淡水鱼类入侵种的分布、入侵途径、机制与后果

生物入侵已经成为全球面临的三大环境问题之一。鱼类入侵现象也随全球经济一体化的进程日益严重。本文综述了全球淡水鱼类入侵的现状和研究进展, 包括鱼类入侵的定义及分布、入侵途径和机制、产生的生态和社会经济影响以及预防措施等。据统计, 目前全球外来鱼类达624种, 该数量超过30年前的两倍。外来鱼类主要通过水产养殖(51%)、观赏渔业(21%)、休闲垂钓(12%)、渔业捕捞运输(7%)等多种途径被引进。入侵鱼类对本地种产生了捕食、种内种间竞争、杂交和疾病传播等负面影响, 破坏本地生态系统, 但是其正面的生态及社会经济影响也不可忽略。近20年来全球鱼类入侵日益受到重视, 相关论文发表数量翻了8倍。值得提出的是, 近10年来全球鱼类入侵风险评价系统的研究显著增加, 一些鱼类入侵模型已应用于五大洲的多个国家。我国淡水外来鱼类共计439种。然而, 我国关于鱼类入侵的研究起步较晚, 发表文献数仅占全球的3.7%, 且主要研究方向仍集中在入侵物种的分布及生物学特性等基础研究上, 缺乏对于鱼类入侵机制及风险评价预测的研究。因此, 我们建议: (1)开展全国范围的本底调查并建立数据库, 实现数据共享, 明确鱼类入侵的历史与分布现状; (2)联合多个政府部门和机构, 对鱼类入侵进行长期观测, 从整个水生生态系统的角度出发, 深入了解其入侵机制及其产生的正面和负面生态和社会经济影响; (3)加强增殖放流的科学研究和管理; (4)构建区域性外来鱼类入侵风险评价系统, 有效预测鱼类入侵活动, 评价入侵种的危害, 并为相关政府部门的决策提供科学依据。     

Global distribution,entry routes,mechanisms and consequences of invasive freshwater fish

Biological invasion is now considered one of the three major environmental issues worldwide. Freshwater fish invasion becomes more serious with globalization of the world economy. We reviewed the current status of global freshwater fish invasions and discussed the definitions, distributions, introduction pathways, mechanisms, ecological and economic impacts, and risk assessments of freshwater fish invasions. Non-native fish are mainly introduced through food aquaculture (51%), as ornamental fish (21%), or for sport fishing (12%) and fisheries (7%). The number of introduced fish has reached 624 species, doubled the number found thirty years ago. Successful invasions may bring many negative ecological consequences, such as predation, hybridization, structure and function alteration of local freshwater ecosystems, as well as diseases transmission. However, it also brings positive biological and economic values. The number of fish invasion studies has increased eight times over the last 20 years, with studies mainly focusing on biology and the biological impact of invasive fish species. Risk assessments of freshwater fish invasions were studied over the last 10 years, and fish invasiveness screening models have been applied in countries of five continents. The number of non-native freshwater fish in China totaled 439. However, research papers on freshwater fish invasions in China was only 3.7% of the global total, and these researches were mainly on the distribution and biology of invasive fish species, and very few studies included risk assessments. Therefore, we suggest investigating the history, distribution, and mechanisms of invasive species at the national level, evaluating both the positive and negative effects of freshwater fish invasions, and also reinforcing studies of risk assessments in China.     

Reduced vertebrate diversity independent of spatial scale following feral swine invasions

Biological invasions often have contrasting consequences with reports of invasions decreasing diversity at small scales and facilitating diversity at large scales. Thus, previous literature has concluded that invasions have a fundamental spatial scale‐dependent relationship with diversity. Whether the scale‐dependent effects apply to vertebrate invaders is questionable because studies consistently report that vertebrate invasions produce different outcomes than plant or invertebrate invasions. Namely, vertebrate invasions generally have a larger effect size on species richness and vertebrate invaders commonly cause extinction, whereas extinctions are rare following invertebrate or plant invasions. In an agroecosystem invaded by a non‐native ungulate (i.e., feral swine, Sus scrofa), we monitored species richness of native vertebrates in forest fragments ranging across four orders of magnitude in area. We tested three predictions of the scale‐dependence hypothesis: (a) Vertebrate species richness would positively increase with area, (b) the species richness y‐intercept would be lower when invaded, and (c) the rate of native species accumulation with area would be steeper when invaded. Indeed, native vertebrate richness increased with area and the species richness was 26% lower than should be expected when the invasive ungulate was present. However, there was no evidence that the relationship was scale dependent. Our data indicate the scale‐dependent effect of biological invasions may not apply to vertebrate invasions.     

Coupling long-term studies with meta-analysis to investigate impacts of non-native crayfish on zoobenthic communities

1. Biological invasions are widely recognised as a significant component of human‐caused environmental change and a primary threat to native biodiversity. The negative impacts of species invasions are particularly evident for freshwater crayfish faunas. 2. This study provides novel insight into the ecological effects of native and non‐native crayfish on zoobenthic communities (with emphasis on the non‐native rusty crayfish, Orconectes rusticus) across broad scales by combining a meta‐analysis of small‐scale experimental studies with a long‐term observational study conducted over a 24 year period in Sparkling Lake, Wisconsin, U.S.A. (46°00′N, 89°42′W). 3. The meta‐analysis summarised quantitatively the results of cage experiments for seven species of crayfish spanning four continents. We found that total zoobenthos densities (primarily Gastropoda and Diptera) were significantly lower in treatments containing crayfish relative to controls; a result that was significant for non‐native crayfish but not for crayfish in their native range, perhaps owing to a small sample size. In contrast to other species, rusty crayfish were also negatively associated with Ephemeroptera. 4. Results from the time series analysis comparing temporal trends in rusty crayfish and invertebrate abundances from Sparkling Lake were consistent with the findings from the meta‐analysis. Rusty crayfish were negatively correlated with the abundance of total zoobenthos, Diptera, Ephemeroptera and Odonata, as well as families of Trichoptera. 5. By coupling the results from short and long‐term research, our study offers greater insight into the nature of crayfish‐invertebrate interactions in aquatic systems, revealing consistent effects of invasive crayfish on native fauna. The control and management of invasive species is facilitated by the knowledge that well executed small‐scale studies may be extrapolated to understand larger‐scale ecological interactions.     

Niche expansion in a resilient endemic species following introduction of a novel top predator

相似文献   

Niche conservatism among non‐native vertebrates in Europe and North America

Niche conservatism, the hypothesis that niches remain constant through time and space, is crucial for the study of biological invasions as it underlies native‐range based predictions of invasion risk. Niche changes between native and non‐native populations are increasingly reported. However, it has been argued that these changes arise mainly because in their novel range, species occupy only a subset of the environments they inhabit in their native range, and not because they expand into environments entirely novel to them. Here, using occurrences of 29 vertebrate species native to either Europe or North America and introduced into the other continent, we assess the prevalence of niche changes between native and non‐native populations and assess whether the changes detected are caused primarily by native niche unfilling in the non‐native range rather than by expansion into novel environments. We show that niche overlap between native and non‐native populations is generally low because of a large degree of niche unfilling in the non‐native range. This most probably reflects an ongoing colonization of the novel range, as niche changes were smaller for species that were introduced longer ago and into a larger number of locations. Niche expansion was rare, and for the few species exhibiting larger amounts of niche overlap, an unfilling of the niche in the native range (e.g. through competition or dispersal limitations) is the most probable explanation. The fact that for most species, the realized non‐native niche is a subset of the realized native niche allows native‐range based niche models to generate accurate predictions of invasion risk. These results suggest that niche changes arising during biological invasions are strongly influenced by propagule pressure and colonization processes, and we argue that introduction history should be taken into account when evaluating niche conservatism in the context of biological invasions.     

Morphological and life‐history responses of anurans to predation by an invasive crayfish: an integrative approach

Predator‐induced phenotypic plasticity has been widely documented in response to native predators, but studies examining the extent to which prey can respond to exotic invasive predators are scarce. As native prey often do not share a long evolutionary history with invasive predators, they may lack defenses against them. This can lead to population declines and even extinctions, making exotic predators a serious threat to biodiversity. Here, in a community‐wide study, we examined the morphological and life‐history responses of anuran larvae reared with the invasive red swamp crayfish, Procambarus clarkii, feeding on conspecific tadpoles. We reared tadpoles of nine species until metamorphosis and examined responses in terms of larval morphology, growth, and development, as well as their degree of phenotypic integration. These responses were compared with the ones developed in the presence of a native predator, the larval dragonfly Aeshna sp., also feeding on tadpoles. Eight of the nine species altered their morphology or life history when reared with the fed dragonfly, but only four when reared with the fed crayfish, suggesting among‐species variation in the ability to respond to a novel predator. While morphological defenses were generally similar across species (deeper tails) and almost exclusively elicited in the presence of the fed dragonfly, life‐history responses were very variable and commonly elicited in the presence of the invasive crayfish. Phenotypes induced in the presence of dragonfly were more integrated than in crayfish presence. The lack of response to the presence of the fed crayfish in five of the study species suggests higher risk of local extinction and ultimately reduced diversity of the invaded amphibian communities. Understanding how native prey species vary in their responses to invasive predators is important in predicting the impacts caused by newly established predator–prey interactions following biological invasions.     

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.     

Poised to prosper? A cross‐system comparison of climate change effects on native and non‐native species performance

Climate change and biological invasions are primary threats to global biodiversity that may interact in the future. To date, the hypothesis that climate change will favour non‐native species has been examined exclusively through local comparisons of single or few species. Here, we take a meta‐analytical approach to broadly evaluate whether non‐native species are poised to respond more positively than native species to future climatic conditions. We compiled a database of studies in aquatic and terrestrial ecosystems that reported performance measures of non‐native (157 species) and co‐occurring native species (204 species) under different temperature, CO₂ and precipitation conditions. Our analyses revealed that in terrestrial (primarily plant) systems, native and non‐native species responded similarly to environmental changes. By contrast, in aquatic (primarily animal) systems, increases in temperature and CO₂ largely inhibited native species. There was a general trend towards stronger responses among non‐native species, including enhanced positive responses to more favourable conditions and stronger negative responses to less favourable conditions. As climate change proceeds, aquatic systems may be particularly vulnerable to invasion. Across systems, there could be a higher risk of invasion at sites becoming more climatically hospitable, whereas sites shifting towards harsher conditions may become more resistant to invasions.     

Detection of native-alien populations of Anisandrus dispar (Fabricius, 1792) in Europe

The human-mediated introduction and movement of alien populations of species within their native range is still a little-explored topic. This phenomenon may cause genetic contamination of local populations and be the introduction pathway of new associated microorganisms and fungi, potentially able to modify the interspecific relationships between insects and host-plants with serious ecological and economic impacts. In the present contribution, we produced the first evidence of a native-alien population of the Palearctic ambrosia beetle Anisandrus dispar occurring in Europe, highlighting that individuals belonging to different populations of a species can disperse via commercial trade within its native biogeographic range resulting in cryptic invasions. Our findings support the idea that the movement of native species within their native distribution range can be more common than previously suspected.