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81.
The spread of alien plant species is a critical ecological event worldwide, but the forces that control this spread are not
well documented. Alien plant species are well known to disrupt ecological services of native ecosystems, change the composition
of native habitats, and often lead to the extirpation of native flora and fauna. Here, we report on life history patterns
of plant species with rapidly spreading and declining ranges in North America’s major urban region. We tested for differences
in life history traits between the 466 native and alien woody flora of the New York metropolitan area. We also examined the
relationship between life history traits and change in distribution in the New York metropolitan area between 1900 and 2000.
Native and alien species of the New York metropolitan area differ with respect to pollination vector and breeding system.
However, pollination vector and breeding system are not associated with success, defined here as increasing range spread in
the urban environment; instead, fruit type (dispersal), life form and origin are important determinants of success. Alien
species that are deciduous trees, shrubs or vines with fleshy fruit are the most successful in increasing their distribution
in this urban landscape. Newly introduced species with these characteristics are expected to have a better chance at establishing
in similar urban landscapes and should be targets for intensive management. The ability to predict which alien species will
become invasive is also a valuable tool for the prevention of invasions by newly introduced plant species. 相似文献
82.
Russell H. Messing Michelle N. Tremblay Edward B. Mondor Robert G. Foottit Keith S. Pike 《Biological invasions》2007,9(5):601-607
Invasive species have had devastating impacts on the fauna and flora of the Hawaiian Islands. While the negative effects of
some invasive species are obvious, other species are less visible, though no less important. Aphids (Homoptera: Aphididae)
are not native to Hawai’i but have thoroughly invaded the Island chain, largely as a result of anthropogenic influences. As
aphids cause both direct plant feeding damage and transmit numerous pathogenic viruses, it is important to document aphid
distributions and ranges throughout the archipelago. On the basis of an extensive survey of aphid diversity on the five largest
Hawaiian Islands (Hawai’i, Kaua’i, O’ahu, Maui, and Moloka’i), we provide the first evidence that invasive aphids feed not
just on agricultural crops, but also on native Hawaiian plants. To date, aphids have been observed feeding and reproducing
on 64 native Hawaiian plants (16 indigenous species and 48 endemic species) in 32 families. As the majority of these plants
are endangered, invasive aphids may have profound impacts on the island flora. To help protect unique island ecosystems, we
propose that border vigilance be enhanced to prevent the incursion of new aphids, and that biological control efforts be renewed
to mitigate the impact of existing species. 相似文献
83.
New statistical modelling methods, such as neural networks (NNs), allow us to take a step further in the understanding of
complex relations in aquatic ecosystems. In this paper the results from the analysis of macro-invertebrate communities in
a complex riverine environment are presented. We attempted to explain observed changes in species composition and abundance
with neural network modelling methods and compared the results to linear regression. The NN method used is an improved form
of the RF5 algorithm, developed to effectively discover numeric laws from data. RF5 uses Product Unit Networks (PUNs), which
are in effect multivariate non-discrete power functions. The data set consisted of a 10-year time series of monthly samples
of macro-invertebrates on artificial substrates in the rivers Rhine and Meuse in the Netherlands. During this period the invertebrate
community has largely changed coinciding with the␣invasion of Ponto-Caspian crustaceans. We used physical–chemical data and
data on the abundance of the invasive taxa Corophium curvispinum and Dikerogammarus villosis to explain the observed changes in the resident invertebrate community. The analyses showed temperature, abundance of invasive
taxa and peak discharges as important factors. Comparison of the results from NN modelling to linear regression revealed that
the factors temperature and abundance of Dikerogammarus
villosis explained equally well in both cases. Only the neural network was able to use information on peak discharge and timing of
the peak in the previous winter to improve model performances. Neural networks are known to yield excellent modelling results,
a drawback however is their lack of transparency or their ‘black box’ character. The use of relatively easy interpretable
(white box) PUNs allows us to investigate the extracted relations in more detail and can enhance our understanding of ecosystem
functioning. Our results show that peak discharges might be an important factor structuring invertebrate communities in rivers
and hint on the existence of interacting effects from invasive species and discharge peaks. They finally show the value of
biological data sets that are collected over a long period and in a highly standardised way. 相似文献
84.
Biological invasions can impact the abundance and diversity of native species, but the specific mechanisms remain poorly discerned.
In California grasslands, invasion by European annual grasses has severely reduced the quality of habitat for native forb
species. To understand how introduced grasses suppress native and exotic forbs, we examined the response of a Southern California
grassland community to factorial removals of live grass and the litter produced in previous seasons. To examine the role that
belowground competition for water plays in mediating the impact of grasses, we crossed grass and litter removal treatments
with water addition. Our results show that forbs were almost equally suppressed by both competition from live grass and direct
interference by litter. Water addition did not ameliorate the effect of grass competition, suggesting that water was not the
resource for which plants compete. This evidence is consistent with the susceptibility of forbs to light limitation, especially
considering that litter does not consume water or nutrients. Interestingly, despite different histories of co-occurrence with
annual grass dominants, native and exotic forbs were comparably suppressed by exotic grasses. Our results indicate that suppression
by both live and dead stems underlie the influence of exotic grasses on forb competitors. 相似文献
85.
Question: Is native species occurrence related to soil nutrients in highly invaded Californian annual grasslands? What is the best method to analyze this relationship, given that native species occur in very low numbers and are absent from many locations? Location: California, USA. Methods: We investigated the effects of soil characteristics and livestock grazing on native plant occurrence at 40 plots from six sites during the period 2003–2005. Low absolute cover (< 5.8%) of native species resulted in strongly skewed, zero-inflated data sets. To overcome problems in the analysis created by non-normality and correlations within plots, we used GLMs and GLMMs, either with a Poisson or a negative binomial distribution, to analyse native species richness and Nassella pulchra cover. Results: N. pulchra cover was strongly associated with low phosphorus in sandy soils, whereas native species richness was highest in soils with low available nitrogen (high C:N). Conclusion: Under current conditions, phosphorus seems to be a critical factor influencing abundance of N. pulchra. Low fertility soils may provide refugia for native species in highly invaded California grasslands as they may be below a threshold required for non-native annuals to completely dominate. By using non-normal distributions in linear models with random components, we report well fitted models with more accurately tested significant covariates. 相似文献
86.
Invasive plants that most threaten biodiversity are those that rapidly form a monospecific stand, like the clonal grass, Phalaris arundinacea. Understanding complex and potentially interacting factors that are common in urban and agricultural landscapes and underlie
rapid invasions requires an experimental, factorial approach. We tested the effects of flooding and nutrient and sediment
additions (3 × 3 × 3 = 27 treatments, plus a control with no additions) on invasion of Phalaris into mesocosms containing wet prairie vegetation. We discovered a three-step invasion and degradation process: (1) initially,
resident native species declined with prolonged flooding and sediment additions, and (2) prolonged flooding, sedimentation,
and nutrients accelerated Phalaris aboveground growth; biomass rose to 430 times that of the control within just two growing seasons. The dramatic expansion
of Phalaris in the second year resulted in the formation of monospecific stands in over one-third of the treatments, as (3) native species
continued their decline in year 2. Disturbances acted alone and in combination to make the resident wetland community more
invasible and Phalaris more aggressive, leading to monospecific stands. Yet, Phalaris did not always “win”: under the least disturbed conditions, the resident plant canopy remained dense and vigorous and Phalaris remained small. When anthropogenic disturbances coincide with increases in the gross supply of resources, more tolerant,
fast-growing, and morphologically plastic plants like Phalaris can invade very rapidly. The fluctuating resource hypothesis should thus be refined to consider the role of interacting disturbances
in facilitating invasions. 相似文献
87.
Kathleen S. Knight Jessica S. Kurylo Anton G. Endress J. Ryan Stewart Peter B. Reich 《Biological invasions》2007,9(8):925-937
In this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits
including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual
phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success
in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance
and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions,
unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be
able to use it for food or habitat. 相似文献
88.
Christian Lavoie C. Josh Donlan Karl Campbell Felipe Cruz G. Victor Carrion 《Biological invasions》2007,9(2):139-148
Non-native mammals are major drivers of ecosystem change and biodiversity loss; this is especially apparent on islands. However,
techniques exist to remove non-native mammals, providing a powerful conservation tool. Conservation practitioners are now
targeting larger islands for restoration. Leveraging existing and developing new techniques and technologies will prove critical
to successful eradications on large islands. Using the removal of introduced goats (Capra hircus) from Santiago Island, Galápagos as a case study, we present a suite of Geographic Information System (GIS) tools that aid
island conservation actions. GIS tools were incorporated into the three phases of the eradication campaign: planning, hunting,
and monitoring. Further, these tools were adopted for three eradication techniques: ground-based hunting, aerial hunting by
helicopter, and Judas goats. These geographic approaches provide a foundation for statistical, spatial, and economic analyses
that should increase the capability and efficiency of removal campaigns. Given limited conservation funds and the dire status
of many insular species, efficiently removing non-native mammals from islands is of paramount global conservation importance. 相似文献
89.
John W. Chapman James T. Carlton M. Renee Bellinger April M. H. Blakeslee 《Biological invasions》2007,9(8):995-1008
The closely documented spread of the European periwinkle snail, Littorina littorea from Pictou, Nova Scotia in 1840 to New Jersey by 1870, its near absence in pre-European fossil deposits, and its close association
with human mechanisms of transport from Europe, are among the clearest evidence of a human-mediated marine introduction ever
reported. Genetic data were recently proposed as evidence that North American L. littorea predate European contact and thus, are not introduced. Review of these genetic data and all other data reveals that the simplest
explanation of the modern occurrence of this snail in North America is by human introduction. 相似文献
90.