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1.
The intentional introduction of exotic species can increase the level of local biodiversity, enrich people's material lives, and bring significant social and economic benefits that are also the symbols of human progress. However, along with the frequent intercourse among countries and regions, the frequency of uncontrolled crossregional migration of species is increased and there is a lack of scientific management strategy for the intentional introduction of exotic species. Exotic species invasion, which is behind habitat fragmentation, has become the second largest threatening factor to the maintenance of the global-scale level of biological diversity. Exotic species invasion can destroy the structure of an ecosystem, disturb the economic life of a society, and do harm to human health. In this paper, the authors review some of the ecological explanations for issues such as "what causes or mechanisms have led to the successful invasion of exotic species", including the "ideal weeds characteristics", "biodiversity resistance hypothesis", "enemies release hypothesis", "evolution of increased competitive ability hypothesis", "niche opportunity hypothesis", and "novel weapon hypothesis". The authors also analyze and evaluate the background and theoretical basis of the hypotheses, providing explanations for some phenomena, as well as the deficiencies of these explanations. 相似文献
2.
Peter Alpert 《Biological invasions》2006,8(7):1523-1534
Introduced species, those dispersed outside their natural ranges by humans, now cause almost all biological invasions, i.e.,
entry of organisms into habitats with negative effects on organisms already there. Knowing whether introduction tends to give
organisms specific ecological advantages or disadvantages in their new habitats could help understand and control invasions.
Even if no specific species traits are associated with introduction, introduced species might out-compete native ones just
because the pool of introduced species is very large (“global competition hypothesis”). Especially in the case of intentional
introduction, high initial propagule pressure might further increase the chance of establishment, and repeated introductions
from different source populations might increase the fitness of introduced species through hybridization. Intentional introduction
screens species for usefulness to humans and so might select for rapid growth and reproduction or carry species to suitable
habitats, all which could promote invasiveness. However, trade offs between growth and tolerance might make introduced species
vulnerable to extreme climatic events and cause some invasions to be transient (“reckless invader hypothesis”). Unintentional
introduction may screen for species associated with human-disturbed habitats, and human disturbance of their new habitats
may make these species more invasive. Introduction and natural long-distance dispersal both imply that species have neither
undergone adaptation in their new habitats nor been adapted to by other species there. These two characteristics are the basis
for many well-known hypotheses about invasion, including the “biotic resistance”, “enemy release”, “evolution of increased
competitive ability” and “novel weapon” hypotheses, each of which has been shown to help explain some invasions. To the extent
that biotic resistance depends upon local adaption by native species, altering selection pressures could reduce resistance
and promote invasion (“local adaptation hypothesis”), and restoring natural regimes could reverse this effect. 相似文献
3.
Novel or emergent ecosystems arising from human action present both threats and opportunities for biodiversity. It has been
suggested that exotic species can “facilitate” or “inhibit” native biodiversity through habitat modification. In Britain,
there is a discussion over the contribution to biodiversity of plantations of exotic conifer species as these are commonly
thought to have little relevancy as a habitat for native biodiversity. To address this we compared the species richness of
a range of different taxonomic groups (lichens, bryophytes, fungi, vascular plants, invertebrates and songbirds) in exotic
and native forest stands of differing structural stages in northern and southern Britain. In terms of overall native species-richness
there was no significant difference between the exotic and the native stands. In the north, six species groups showed higher
values in the exotic Sitka spruce (Picea sitchensis) stands with the remaining six showing higher values in the native Scots pine (Pinus sylvestris) stands. Most notably, lichen species richness was much lower in the exotic stands compared to the native stands, whereas
bryophyte and fungal species richness was proportionately higher in the exotic stands. In the south, five species groups (all
invertebrate taxa) showed higher species richness in exotic Norway spruce (Picea abies) stands compared to native oak (Quercus robur) stands. Five species groups had higher species-richness in the oak stands, in particular lichens and fungi. It is concluded
that emergent ecosystems of exotic conifer species are not irrelevant to biodiversity. Where already well-established they
can provide habitat for native species particularly if native woodland is scarce and biodiversity restoration is an immediate
priority. 相似文献
4.
Saving camels from straws: how propagule pressure-based prevention policies can reduce the risk of biological invasion 总被引:1,自引:0,他引:1
Nonnative species that harm or have the potential to cause harm to the environment, economy, or human health are known as
invasive species. Propagule pressure may be the most important factor in establishment success of nonnative species of various
taxa in a variety of ecosystems worldwide, and strong evidence is emerging that propagule pressure determines both the scale
of invasion extent and impact. In a limited way, the US government is applying a “propagule pressure approach” in a variety
of prevention policy contexts aimed at minimizing the impact of harmful organisms. However, there are also readily apparent
opportunities for enacting propagule pressure-based measures to fill current gaps in invasive species prevention and control
at national, state, and local levels. An explicit focus on propagule pressure-based policies could substantially increase
the effectiveness of US efforts to prevent the introduction of invasive species through by intentional and unintentional introductions.
The views expressed in this paper are solely those of the authors and do not necessarily reflect those of the US government.
“As the last straw breaks the laden camel’s back...”
-Charles Dickens, Dombey and Son 相似文献
5.
6.
Forestry is obliged to record as well as maintain and/or enhance biological diversity in forests due to national and international
agreements. Accordingly, it is necessary to work out methodological approaches for the assessment of biodiversity in forests.
In the study presented here, we focus on the total plant species pool (563 vascular plant and bryophyte species) of pine (Pinus sylvestris L.) forests in NE Germany to identify indicators for plant species richness. We distinguished several groups like “herb”,
“grass-like”, “woody”, “endangered”, and “exotic species”, for which we detected indicators for low (class #1), intermediate
(class #2), and high (class #3) species numbers. From a total of 84 species, which were identified by a three-step procedure,
most indicators were found for class #3. Only few indicators have been revealed for intermediate species numbers, i.e. class
#2. With help of Ellenberg’s ecological indicator values and information on the main occurrence in Central European vegetation
types and plant communities, respectively, we characterized the indicator species ecologically. The ecological site preferences
of the indicator species in general reflect the fact that species richness is highest in base-rich, light, and anthropogenically
disturbed pine forests. On the contrary, species-poor forests were revealed by indicators, which mainly occur on acidic sites.
It is concluded that a considerable set of indicators for species richness can help facilitate biodiversity assessments in
forestry and ecosystem restoration practice.
Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
7.
Michael P. Moulton Wendell P. Cropper Jr. Linda E. Moulton Michael L. Avery David Peacock 《Biodiversity and Conservation》2012,21(1):155-174
Introduced species are widely believed to represent a significant threat to conservation of biological diversity. A better
understanding of the ecological factors associated with successful species establishment should lead to improved management
and mitigation of these introductions. The “propagule pressure hypothesis”, implying a greater chance of successful introduction
with greater numbers introduced, has been widely accepted as a principal ecological factor in explaining establishment of
exotic species. The historical record of bird introductions in a few locations, including the state of Victoria in Australia,
has been advanced as the principal quantitative support for the hypothesis. We compiled lists of bird species introductions
into Australia from several sources, and discovered inconsistencies in the records of introductions. In a series of comparisons,
we found that the historical record of passerine introductions to Australia does not support the propagule pressure hypothesis
unless superfluous introductions of already successful species are included. An additional problem with previous analyses
is the inclusion of unsuccessful haphazard cage escapes. 相似文献
8.
Plant community diversity and native plant abundance decline with increasing abundance of an exotic annual grass 总被引:1,自引:0,他引:1
Davies KW 《Oecologia》2011,167(2):481-491
Exotic plants are generally considered a serious problem in wildlands around the globe. However, some argue that the impacts
of exotic plants have been exaggerated and that biodiversity and other important plant community characteristics are commonly
improved with invasion. Thus, disagreement exists among ecologists as to the relationship of exotic plants with biodiversity
and native plant communities. A better understanding of the relationships between exotic plants and native plant communities
is needed to improve funding allocation and legislation regarding exotic plants, and justify and prioritize invasion management.
To evaluate these relationships, 65 shrub–bunchgrass plant communities with varying densities of an exotic annual grass, Taeniatherum caput-medusae (L.) Nevski (medusahead), were sampled across 160,000 ha in southeastern Oregon, United States. Environmental factors were
generally not correlated with plant community characteristics when exotic annual grass density was included in models. Plant
diversity and species richness were negatively correlated with exotic annual grass density. Exotic annual grass density explained
62% of the variation in plant diversity. All native plant functional groups, except annual forbs, exhibited a negative relationship
with T. caput-medusae. The results of this study suggest that T. caput-medusae invasions probably have substantial negative impacts on biodiversity and native plant communities. The strength of the relationships
between plant community characteristics and T. caput-medusae density suggests that some exotic plants are a major force of change in plant communities and subsequently threaten ecosystem
functions and processes. However, experimental studies are needed to fully substantiate that annual grass invasion is the
cause of these observed correlations. 相似文献
9.
Roderic D. M. Page 《Organisms Diversity & Evolution》2010,10(4):343-349
In a 2003 essay E. O. Wilson outlined his vision for an “encyclopaedia of life” comprising “an electronic page for each species
of organism on Earth”, each page containing “the scientific name of the species, a pictorial or genomic presentation of the
primary type specimen on which its name is based, and a summary of its diagnostic traits.” Although biodiversity informatics
has generated numerous online resources, including some directly inspired by Wilson’s essay (e.g., iSpecies and EOL), we are
still some way from the goal of having available online all relevant information about a species, such as its taxonomy, evolutionary
history, genomics, morphology, ecology, and behaviour. While the biodiversity community has been developing a plethora of
databases, some with overlapping goals and duplicated content, Wikipedia has been slowly growing to the point where it now
has over 100,000 pages on biological taxa. My goal in this essay is to explore the idea that, largely independent of the aims
of biodiversity informatics and well-funded international efforts, Wikipedia has emerged as potentially the best platform
for fulfilling E. O. Wilson’s vision. 相似文献
10.
Exotic species richness and native species endemism increase the impact of exotic species on islands
Jessica C. Walsh Oscar Venter Richard A. Fuller Tim M. Blackburn Hugh P. Possingham 《Global Ecology and Biogeography》2012,21(8):841-850
Aim Exotic species pose one of the most significant threats to biodiversity, especially on islands. The impacts of exotic species vary in severity among islands, yet little is known about what makes some islands more susceptible than others. Here we determine which characteristics of an island influence how severely exotic species affect its native biota. Location We studied 65 islands and archipelagos from around the world, ranging from latitude 65° N to 54° S. Methods We compiled a global database of 10 island characteristics for 65 islands and determined the relative importance of each characteristic in predicting the impact of exotic species using multivariate modelling and hierarchical partitioning. We defined the impact of exotic species as the number of bird, amphibian and mammal (BAM) species listed by the International Union for Conservation of Nature (IUCN) as threatened by exotics, relative to the total number of BAM species on that island. Results We found that the impact of exotic species is more severe on islands with more exotic species and a greater proportion of native species that are endemic. Unexpectedly, the level of anthropogenic disturbance did not influence an island's susceptibility to the impacts of exotic species. Main conclusions By coupling our results with studies on the introduction and establishment of exotic species, we conclude that colonization pressure, or invasion opportunities, influences all stages of the invasion process. However, species endemism, the other important factor determining the impact of exotic species, is not known to contribute to introduction and establishment success on islands. This demonstrates that different factors correlate with the initial stages of the invasion process and the subsequent impacts of those invaders, highlighting the importance of studying the impacts of exotic species directly. Our study helps identify islands that are at risk of impact by exotics and where investment should focus on preventing further invasions. 相似文献
11.
Helen E. Roy Patrick De Clercq Lori-Jayne Lawson Handley Remy L. Poland John J. Sloggett Eric Wajnberg 《BioControl》2011,56(4):375-382
Invasive alien species (IAS) coupled with climate change have been referred to as a “deadly duo”. Until recently research
on invasion biology has centred mainly on alien plants and vertebrates, despite the numerical dominance of alien arthropods.
Arthropods are the largest group of IAS worldwide and many can play a beneficial role, particularly in controlling insect
and mite pests. Indeed, 1590 terrestrial arthropod species have been identified as alien to Europe but only a fraction has
been shown to cause either an ecological or economical impact, yet knowledge is severely limited by a paucity of data. The
IOBC/WPRS Working Group “Benefits and Risks of Exotic Biological Control Agents” developed the theme of this special issue
to begin to address the limitations in understanding of this important research area. It represents a timely synthesis of
current ecological knowledge and research on alien arthropod predators and parasitoids. 相似文献
12.
Stefano Scalercio Roberto Pizzolotto Pietro Brandmayr 《Biodiversity and Conservation》2007,16(12):3463-3479
This paper is an attempt to outline a protocol for animal diversity census and evaluation aimed for areas in view of landscape
planning of territories of hundred square kilometres and more, that may work utilising different faunal groups and be anyway
useful at various scales. Many papers are addressed to elaborate tools for landscape planning starting from biodiversity evaluation
and butterflies are often utilised because of their sensitivity to landscape modifications. In this work, the biodiversity
evaluation has been performed using three hierarchically linked landscape units at micro-, meso- and macroscale. Being species
diversity values often inadequate to define the conservation interest of a landscape portion, more importance has been given
to which species compose the species assemblages. A community vulnerability Index was coded and used for evaluating potential
consequences of human disturbance on butterfly assemblages. Forty-four year samples were gained by visual census in the Sila
Greca, Southern Italy, on an area of approximately 520 square kilometres. During 5 years work, 2,535 specimens and 94 species
were recorded, equal to 75.8% of the whole Calabrian fauna. Four vulnerability levels have been established and used for mapping
butterfly assemblage vulnerability in the area, starting from a vegetation map. Species richness was found somewhat contradictory
at micro-scale, where the community vulnerability Index gives a sounder approach. S diversity gives a more reliable picture of naturalness at meso-scale, a level we identified with the “ecotope”. At this more
“geomorphic” scale level, biological functions reflected by butterfly assemblages revealed to be clearly linked to seral processes.
Similarity analysis results show that the ecotope species richness, here called “eta-diversity”, could be an useful measure
of zoological landscape (faunation) potentialities. 相似文献
13.
Patterns of Plant Invasions: A Case Example in Native Species Hotspots and Rare Habitats 总被引:3,自引:0,他引:3
Thomas J. Stohlgren Yuka Otsuki Cynthia A. Villa Michelle Lee Jayne Belnap 《Biological invasions》2001,3(1):37-50
Land managers require landscape-scale information on where exotic plant species have successfully established, to better guide
research, control, and restoration efforts. We evaluated the vulnerability of various habitats to invasion by exotic plant
species in a 100,000 ha area in the southeast corner of Grand Staircase-Escalante National Monument, Utah. For the 97 0.1-ha
plots in 11 vegetation types, exotic species richness (log10) was strongly negatively correlated to the cover of cryptobiotic soil crusts (r = −0.47, P < 0.001), and positively correlated to native species richness (r = 0.22, P < 0.03), native species cover (r = 0.23, P < 0.05), and total nitrogen in the soil (r = 0.40, P < 0.001). Exotic species cover was strongly positively correlated to exotic species richness (r = 0.68, P < 0.001). Only 6 of 97 plots did not contain at least one exotic species. Exotic species richness was particularly high in
locally rare, mesic vegetation types and nitrogen rich soils. Dry, upland plots (n = 51) had less than half of the exotic species richness and cover compared to plots (n = 45) in washes and lowland depressions that collect water intermittently. Plots dominated by trees had significantly greater
native and exotic species richness compared to plots dominated by shrubs. For the 97 plots combined, 33% of the variance in
exotic species richness could be explained by a positive relationship with total plant cover, and negative relationships with
the cover of cryptobiotic crusts and bare ground. There are several reasons for concern: (1) Exotic plant species are invading
hot spots of native plant diversity and rare/unique habitats. (2) The foliar cover of exotic species was greatest in habitats
that had been invaded by several exotic species.(3) Continued disturbance of fragile cryptobiotic crusts by livestock, people,
and vehicles may facilitate the further invasion of exotic plant species.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The role of trade-offs in biodiversity conservation planning: Linking local management, regional planning and global conservation efforts 总被引:4,自引:0,他引:4
Biodiversity conservation planning requires trade-offs, given the realities of limited resources and the competing demands
of society. If net benefits for society are important, biodiversity assessment cannot occur without other sectoral factors
“on the table”. In trade-offs approaches, the biodiversity value of a given area is expressed in terms of the species or other
components of biodiversity that it has that are additional to the components protected elsewhere. That “marginal gain” is
called thecomplementarity value of the area. A recent whole-country planning study for Papua New Guinea illustrates the importance of complementarity-based
tradeoffs in determining priority areas for biodiversity conservation, and for designing economic instruments such as biodiversity
levies and offsets. Two international biodiversity programs provide important new opportunities for biodiversity trade-offs
taking complementarity into account. Both the Millennium Ecosystem Assessment and the Critical Ecosystems or “hotspots” programs
can benefit from an explicit framework that incorporates tradeoffs, in which a balance is achieved not only by land-use allocation
among areas, but also by the crediting of partial protection of biodiversity provided by sympathetic management within areas.
For both international programs, our trade-offs framework can provide a natural linkage between local, regional and global
planning levels. 相似文献
15.
Daniel J. Larkin 《Biological invasions》2012,14(4):827-838
There are often lag phases in plant invasions, seemingly dormant periods between arrival in a new range and rapid population growth. Lags impede prioritization
of invasive-species control efforts: when eradication is most feasible, it is often unclear whether a species is benign or
a potentially harmful “sleeper weed.” I used herbarium records to estimate lag phases for invasive or potentially invasive
plant species in three regions of the upper Midwest. I tested whether factors related to species’ invasion epidemiology, traits,
or the habitats they invade were correlated with lag lengths. From an initial pool of 151 species, there were sufficient records
to test for lags in 76 for northern Wisconsin, 90 for southern Wisconsin, and 91 for the southern Lake Michigan region. Lags
were identified in 77% (197) of these 257 datasets and ranged from 3–140 years with a mean of 47.3 ± 34.6 (SD). Lags differed
by native range, introduction pathway, growth form and habit, dispersal mode, flowering phenology, pollination mode for a
subset of species, and breadth, light availability, and water availability of invaded habitats. However, estimated lags were
highly variable and tested factors did not have strong explanatory power. Exotic species comprised an increasing proportion
of total herbarium records. Of the species with known introduction pathways, 85% were intentionally introduced, mainly as
ornamentals. The long durations, high variability, and low predictability of lags, along with human culpability for an increasingly
non-native flora, support a cautious approach to species introductions. 相似文献
16.
Robert Stephen Cantrell Chris Cosner William F. Fagan 《Journal of mathematical biology》1998,37(6):491-533
Habitat degradation is the slow – and often subtle – deterioration in habitat quality that accompanies human activities through
increases in road density, pesticide use, hunting pressure, etc. Such degradation is of particular concern in fragmented habitats
where economic or jurisdictional boundaries rather than ecological ones determine the level of exploitation adjoining habitat
patches endure. To examine the consequences habitat degradation might have on species interactions, we posited a patch of
pristine habitat surrounded by “matrix” habitat whose degradation level was variable. Using a coupled pair of diffusive Lotka–Volterra
competition equations with Robin (mixed) boundary conditions, we modeled the dynamics of two competing species inhabiting
the pristine patch and incorporated matrix degradation through a tunable “hostility” parameter representing species’ mortality
rates in the matrix. We found that the numerical range of competition coefficients over which one species is the competitive
dominant and the other inferior may grow or shrink as matrix quality deteriorates. In some cases, degradation of the exterior
habitat would bring about a complete competitive reversal inside the preserve. This result, wherein a formerly inferior species supplants a formerly dominant one – even inside the “protected”
remnant patch itself – has policy implications for both nature reserve design and management of human activities outside park
boundaries.
Received: 30 April 1997 相似文献
17.
Joseph K. Bailey Jennifer A. Schweitzer Brian J. Rehill Duncan J. Irschick Thomas G. Whitham Richard L. Lindroth 《Biological invasions》2007,9(6):715-722
The global ecological impacts of introduced and exotic species can be dramatic, leading to losses in biodiversity and ecosystem
“meltdown”, however, the evolutionary impacts of introduced species are much less understood. Further, very few studies have
examined whether mammalian herbivores can act as agents of natural selection for plant traits. We examined the hypothesis
that variation in aspen phytochemistry resulted in selective herbivory by Cervus elaphus (elk), an introduced mammalian herbivore. With the experimental removal of a large elk exclosure, elk selectively eliminated
60% of an aspen population previously protected from herbivory resulting in a dramatic shift in the phytochemical composition
of the aspen forest. Selection gradients (β) varied from 0.52 to 0.66, well above average relative to other studies of selection.
These results indicate that introduced herbivores can have rapid evolutionary consequences even on long lived native species.
Because there are fundamental links between phytochemistry, biodiversity and ecosystem processes, the effects of an introduced
herbivore are likely to have cascading impacts on the services ecosystems provide. 相似文献
18.
The Laurentian Great Lakes have been subject to numerous introductions of nonindigenous species, including two recent benthic
fish invaders, Eurasian ruffe (Gymnocephalus cernuus) and round gobies (Neogobius melanostomus), as well as the benthic bivalve, zebra mussel (Dreissena polymorpha). These three exotic species, or “exotic triad,” may impact nearshore benthic communities due to their locally high abundances
and expanding distributions. Laboratory experiments were conducted to determine (1) whether ruffe and gobies may compete for
habitat and invertebrate food in benthic environments, and (2) if zebra mussels can alter those competitive relationships
by serving as an alternate food source for gobies. In laboratory mesocosms, both gobies and ruffe preferred cobble and macrophyte
areas to open sand either when alone or in sympatry. In a 9-week goby–ruffe competition experiment simulating an invasion
scenario with a limited food base, gobies grew faster than did ruffe, suggesting that gobies may be competitively superior
at low resource levels. When zebra mussels were added in a short-term experiment, the presence or absence of mussels did not
affect goby or ruffe growth, as few zebra mussels were consumed. This finding, along with other laboratory evidence, suggests
that gobies may prefer soft-bodied invertebrate prey over zebra mussels. Studies of interactions among the “exotic triad”,
combined with continued surveillance, may help Great Lakes fisheries managers to predict future population sizes and distributions
of these invasive fish, evaluate their impacts on native food webs, and direct possible control measures to appropriate species. 相似文献
19.
外来杂草在我国的危害性及其管理对策 总被引:98,自引:3,他引:95
外来杂草已对我国的农作物生产、果园、草坪、环境和生物多样性等赞成了严重危害。外来杂草之所以能在传入地产生危害,与它们所具有的特性和当地缺乏环境阻力密切相关。对外来杂草的管理应从防止外来杂草传入和对现有的外来杂草初稿除两方面采取措施。防止传入的措施包括:(1)加强植物检疫;(2)建立外来植物引种驯化的风险性评价制度;(3)鼓励利用本土植物。对现有外来杂草的防除,则应采取综合性的防除措施:(1)防治生态破坏;(2)开展外来杂草的生物控制;(3)利用经济植物进行生境替代控制;(4)开展对外来杂草的利用。 相似文献
20.
Silvia E. Burkart Rolando J. C. León María C. Conde Susana B. Perelman 《Plant Ecology》2011,212(6):1009-1024
In order to provide a baseline for management decisions, we evaluated vegetation heterogeneity among 38 remnant grasslands
located on high agronomic potential soils along a five degree-east–west transect in the cropping Pampa. This extensive region
has been cultivated for well over a century, small-scale traditional forms of agriculture were progressively replaced with
large-scale industrial forms and its cropped area has more than doubled in the last 25 years, threatening the maintenance
of biodiversity associated to productive soils. We characterized the diversity of this grassland patches, identified its main
environmental drivers and searched for factors that favor their invasion by exotic plant species. Vegetation samples were
analysed through Canonical Correspondence Analysis, proportional distribution of functional groups was compared and regression
models were estimated to identify variables associated with exotic species importance. Water availability, determined by climate
and soil characteristics, was the main driving factor of floristic heterogeneity in these grasslands. Exotic richness, mostly
of Eurasian species, increases toward the east, related to proximity to the entrance port. The functional group of C4 native grasses seems to be responsible for biotic resistance to invasion. More than 80% of the species recorded during the
first vegetation registers in 1930 are still present, while the number of exotics was seven-fold increased. Despite covering
small areas as isolated stands, these are hot spots of native biodiversity and must be the object of increasing attention
for conservation and restoration in order to protect the biodiversity of an extensive agricultural landscape. 相似文献