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1.
David Sternberg Stephen R. Balcombe Jonathan C. Marshall Jaye S. Lobegeiger Angela H. Arthington 《Environmental Biology of Fishes》2012,93(1):95-104
The ecology of dryland rivers is driven by their highly variable hydrology, particularly flooding regimes, whereby intermittent
floods typically generate ‘booms’ of primary and secondary productivity, including massive fish production. We tested these
concepts in the Moonie River, Australia, using the percichthyid, Macquaria ambigua, a dryland river species known to display pronounced ‘boom and bust’ abundance patterns in response to floodplain inundation
followed by extended periods of low to no channel flow. We expected that body condition (as measured by whole body lipid content)
and biomass of M. ambigua would be related to prey biomass, and that these factors would all ‘spike’ following widespread flooding. Instead we found
more subtle responses. There were ‘booms’ in biomass of Macrobrachium and zooplankton, two important food items, whereas M. ambigua maintained relatively low but sustained lipid and biomass levels following flooding. It appears that instead of a ‘boom’
in fish biomass, abundant invertebrate food resources and sustained lipid levels contributed to high survivorship of this
species during the ‘bust’ period over cool dry months. 相似文献
2.
Skylar Craig Sonia Kannadan S. Luke Flory Elizabeth K. Seifert Kenneth D. Whitney Jennifer A. Rudgers 《Symbiosis (Philadelphia, Pa.)》2011,53(1):17-28
Microbial symbionts can improve the competitive ability and stress tolerance of plant hosts and thus may enhance native plant
resistance against invaders. We investigated whether symbiosis between a native grass, Poa alsodes, and a fungal endophyte (Neotyphodium sp.) improved the grass’s ability to compete against Microstegium vimineum (Japanese stiltgrass), a common invader in the eastern USA. We challenged naturally endophyte-symbiotic and experimentally
endophyte-free P. alsodes plants with the invader. In the first experiment, we manipulated symbiosis and water availability to test for context-dependency
in symbiont benefits. In the second experiment, we manipulated symbiosis and M. vimineum diversity (the number of invader populations), since greater intraspecific diversity is expected to improve invasion success
and might alter the efficacy of symbiosis in invasion resistance. In both experiments, presence of the endophyte reduced the
per plant biomass of M. vimineum and increased P. alsodes biomass. We found no evidence that benefits of the symbiont depended on water availability, and population-level diversity
had a minor influence on M. vimineum: inflorescence number showed a parabolic relationship with increasing numbers of M. vimineum populations. Overall, symbiosis in the native grass had stronger effects on invader growth than either water availability
or invader genetic diversity. Our results suggest that endophyte symbioses in native plants can increase host performance
against an invader, although this conclusion needs confirmation in more complex field settings where other important factors,
such as herbivores and fluctuating abiotic conditions, come into play. 相似文献
3.
Plant–soil interactions have been proposed as a causative mechanism explaining how invasive plant species impact ecosystem
processes. We evaluate whether an invasive plant influences plant and soil-microbe acquisition of nitrogen to elucidate the
mechanistic pathways by which invaders might alter N availability. Using a 15N tracer, we quantify differences in nitrogen uptake and allocation in communities with and without Microstegium vimineum, a shade-tolerant, C4 grass that is rapidly invading the understories of eastern US deciduous forests. We further investigate if plants or the
microbial biomass exhibit preferences for certain nitrogen forms (glycine, nitrate, and ammonium) to gain insight into nitrogen
partitioning in invaded communities. Understory native plants and M. vimineum took up similar amounts of added nitrogen but allocated it differently, with native plants allocating primarily to roots
and M. vimineum allocating most nitrogen to shoots. Plant nitrogen uptake was higher in invaded communities due primarily to the increase
in understory biomass when M. vimineum was present, but for the microbial biomass, nitrogen uptake did not vary with invasion status. This translated to a significant
reduction (P < 0.001) in the ratio of microbial biomass to plant biomass nitrogen uptake, which suggests that, although the demand for
nitrogen has intensified, microbes continue to be effective nitrogen competitors. The microbial biomass exhibited a strong
preference for ammonium over glycine and nitrate, regardless of invasion status. By comparison, native plants showed no nitrogen
preferences and M. vimineum preferred inorganic nitrogen species. We interpret our findings as evidence that invasion by M. vimineum leads to changes in the partitioning of nitrogen above and belowground in forest understories, and to decreases in the microbial
biomass, but it does not affect the outcome of plant–microbe–nitrogen interactions, possibly due to functional shifts in the
microbial community as a result of invasion. 相似文献
4.
Restoration sites are vulnerable to plant invasions due to habitat and resource alteration. We conducted an invasive plant-removal
study at a wetland restoration in the North Carolina Piedmont, a site dominated by the non-native invasive, Microstegium vimineum. Paired plots (M. vimineum hand-weeded and unweeded) were established and maintained to monitor response of plant species richness and diversity. Plots
increased from 4 to 15 species m−2 after three growing seasons of M. vimineum removal and 90% of the newly establishing species were native. Weeding ceased in the fourth growing season and M. vimineum rapidly re-invaded. Formerly weeded plots increased to 59% (±11% SE) M. vimineum cover, 25 of 51 plant species disappeared from the plots, and species richness decreased to an average of <8 species m−2. Our results show that we can quickly establish an abundant, diverse community with invasive removal, but that persistent
effort is required to monitor and maintain the long-term viability of this community. 相似文献
5.
The ability of an invasive plant to occupy new areas is often attributed to both morphological and physiological plasticities
that allow them to remain viable over a wide range of environmental conditions. Studies addressing the ecological requirements
of Microstegium vimineum often consider soil moisture or soil moisture along with other factors as important explanatory components for the establishment
and persistence of this invasive monocot. However, controlled studies specifically targeting water relations in M. vimineum are needed. Therefore, the purpose of this study was to determine how different water availabilities influence the growth
and physiological performance of M. vimineum. This study utilized experimental microcosms to achieve different water availabilities including low soil moisture (<15%
water), moderate soil moisture (ca. 20–30%), and flooded conditions. While both flooded and low soil moisture resulted in
diminished growth, M. vimineum still survived under these conditions. Physiological processes including C4 metabolism, minimum stress under low water conditions, and the ability to increase tissue rigidity may confer some advantages
to M. vimineum during periods of limiting water conditions. Similarly, the proportionally low root biomass, shallow root structure, and
its ability to maintain stable water relations during flooding and/or soil waterlogging may facilitate M. vimineum’s ability to invade mesic habitats. It is likely, therefore, that the capacity to tolerate both low soil moistures and flooded
conditions has enhanced the ability of M. vimineum to populate disturbed systems in central North Carolina. 相似文献
6.
Recent findings on feedback between plants and soil microbial communities have improved our understanding of mechanisms underlying
the success and consequences of invasions. However, additional studies to test for feedback in the presence and absence of interspecific competition, which may alter the strength or direction of feedbacks, are needed. We tested for soil
microbial feedback in communities of the invasive grass Microstegium vimineum and commonly co-occurring native plant species. To incorporate competitive context, we used a factorial design with three
plant treatments (M. vimineum alone, M. vimineum with the native plant community, and the native community without M. vimineum) and two soil inoculum treatments (experimentally invaded and uninvaded soil). When competing with M. vimineum, native communities were 27% more productive in invaded than uninvaded soil. In contrast, soil type did not significantly
affect M. vimineum biomass or fecundity. At the community level, these results indicate a net negative soil microbial feedback when native plants
and M. vimineum are grown in competitive mixture, but not when they are grown separately. Since positive, not negative, feedback is associated
with dominance and invasion, our findings do not support plant–soil feedback as a driver of invasion in this species. Our
results do show that the importance of soil feedback can change with competitive context. Such context-dependency implies
that soil feedback may change when competitive interactions between natives and invading species shift as invasions progress. 相似文献
7.
Spread of an invasive grass in closed-canopy deciduous forests across local and regional environmental gradients 总被引:1,自引:0,他引:1
Cynthia D. Huebner 《Biological invasions》2010,12(7):2081-2089
Establishment of Microstegium vimineum, an invasive exotic grass, in closed-canopy U.S. eastern forests was evaluated across a local (roadside to forest interior)
and regional (across two geographic provinces) environmental gradient in West Virginia. The two geographic provinces were
the Allegheny Plateau (more mesic) and the Ridge and Valley Province (more xeric). Biotic, abiotic, and disturbance variables
were measured in (1) systematically located plots, starting from the roadside and extending 50 m into the forests, and (2)
randomly selected, forest interior plots, with equal numbers of plots containing or not containing M. vimineum. Associations between the variables and the presence of M. vimineum at both scales were evaluated using generalized linear models. Relative importance of the variables related to M. vimineum establishment in the forest interior plots at the regional scale was determined using logistic regression. Results confirmed
Microstegium vimineum’s reduced reproductive capacity in the forest interior compared to the roadside. Patches of M. vimineum in the forest interiors across the regional gradient were best defined by high native plant richness and diversity. Greater
canopy opening, more moss, and shallower litter depths were also positively and significantly associated with M. vimineum presence, but only during the driest sample year. 相似文献
8.
MICHAEL S. STRICKLAND JAYNA L. DEVORE JOHN C. MAERZ MARK A. BRADFORD 《Global Change Biology》2010,16(4):1338-1350
Invasive plant species affect a range of ecosystem processes but their impact on belowground carbon (C) pools is relatively unexplored. This is particularly true for grass invasions of forested ecosystems. Such invasions may alter both the quantity and quality of forest floor inputs. Dependent on both, two theories, ‘priming’ and ‘preferential substrate utilization’, suggest these changes may decrease, increase, or leave unchanged native plant‐derived soil C. Decreases are expected under ‘priming’ theory due to increased soil microbial activity. Under ‘preferential substrate utilization’, either an increase or no change is expected because the invasive plant's inputs are used by the microbial community instead of soil C. Here, we examine how Microstegium vimineum affects belowground C‐cycling in a southeastern US forest. Following predictions of priming theory, M. vimineum's presence is associated with decreases in native‐derived, C pools. For example, in September 2006 M. vimineum is associated with 24%, 34%, 36%, and 72% declines in total organic, particulate organic matter, mineralizable (a measure of microbially‐available C), and microbial biomass C, respectively. Soil C derived from M. vimineum does not compensate for these decreases, meaning that the sum of native‐ plus invasive‐derived C pools is smaller than native‐derived pools in uninvaded plots. Supporting our inferences that C‐cycling accelerates under invasion, the microbial community is more active per unit biomass: added 13C‐glucose is respired more rapidly in invaded plots. Our work suggests that this invader may accelerate C‐cycling in forest soils and deplete C stocks. The paucity of studies investigating impacts of grass invasion on C‐cycling in forests highlights the need to study further M. vimineum and other invasive grasses to assess their impacts on C sink strength and forest fertility. 相似文献
9.
The theoretical foundations of population and community ecology stress the importance of identifying crucial niche requirements
and life history stages of invasive species and, in doing so, give insight into research and management. We focus on Microstegium vimineum, an invasive grass which is causing marked changes in the structure and function of US forests. We describe M. vimineum’s life history and habitat characteristics, infer its niche requirements and synthesize this information in the context of
population dynamics and management. Based on the results synthesized here, M. vimineum’s crucial niche requirements appear to be light (reproductive output), soil moisture (reproductive output, seedling recruitment)
and aboveground coverage by leaf-litter and competing species (seedling recruitment and survival). These data suggest a source-sink
dynamic might allow M. vimineum to disperse and thrive along sunny, and sometimes wet, edge habitats and, in turn, these populations might act as source
populations for adjacent shady forest habitats. By evaluating M. vimineum in the context of its stage-specific requirements, we highlight potential weaknesses in its life history that provide strategies
for effective management. 相似文献
10.
K. Sorkheh B. Shiran M. Khodambshi V. Rouhi S. Ercisli 《Plant Cell, Tissue and Organ Culture》2011,105(3):395-404
Eight native Iranian almond species from three sections, ‘Euamygdalus’ (Prunus communis; Prunus eleagnifolia and Prunus orientalis); ‘Lycioides’ (Prunus lycioides and Prunus reuteri) and ‘Spartioides’ (Prunus arabica, Prunus glauca and Prunus scoparia) were in vitro screened for drought tolerance using sorbitol and polyethylene glycol (PEG) as an osmoticum. Different levels
of water stress were induced using five concentrations of either sorbitol or polyethylene glycol in Woody Plant Medium (WPM).
Water potential of various media ranged from −0.80 to −2.05 MPa and water stress in culture medium adversely affected plantlet
growth. Wild species from ‘Spartioides’ were less affected than ‘Lycioides’ and ‘Euamygdalus’. At the same level of water
potential, sorbitol had lower adverse effects than PEG; the latter being severe. Prunus × sorbitol and Prunus × PEG interactions were significant. At 0.2 M sorbitol and 0.003 M PEG, ‘Spartioides’ produced significantly more roots with
higher total root length and root volume, as well as root-dry weight than those of ‘Lycioides’ and ‘Euamygdalus.’ It is concluded
that in vitro screening of native Iranian almond species under specific and limited water-stress conditions may provide a
system for effectively differentiating the wild species of almond for their expected root mass production under field conditions. 相似文献
11.
It is generally accepted that native communities provide resistance against invaders through biotic interactions. However,
much remains uncertain about the types of ecological processes and community attributes that contribute to biotic resistance.
We used experimental mesocosms to examine how zooplankton community structure, invertebrate predation, and nutrient supply
jointly affected the establishment of the exotic Daphnia lumholtzi. We predicted that establishment would increase with declining biomass and diversity of native zooplankton communities and
that an invertebrate predator (IP) would indirectly facilitate the establishment of D. lumholtzi due to its relatively long predator-deterring spines. Furthermore, we hypothesized that elevated nutrient supply would increase
algal food availability and facilitate establishment. Only when the biomass and diversity of native zooplankton were significantly
reduced, was D.␣lumholtzi able to successfully invade mesocosms. Although invertebrate predation and resource supply modified attributes of native
zooplankton communities, they did not influence the establishment of D. lumholtzi. Overall, our␣results are consistent with observed population dynamics in invaded reservoirs where D.␣lumholtzi tends to be present only during the late summer, coinciding with historic mid-summer declines in native zooplankton populations.
Lakes and reservoirs may be more susceptible to invasion not only by D. lumholtzi, but also by other planktonic species, in the late summer when native communities exhibit characteristics associated with
lower levels of biotic resistance. 相似文献
12.
Ilex Vomitoria
Ait. (Yaupon): A Native North American Source of a Caffeinated and Antioxidant-Rich Tea. Yaupon holly (Ilex vomitoria Ait.) is a caffeine-containing shrub native to the southeastern United States where its leaves and twigs were traditionally
used to prepare a stimulating and healthful beverage by Amerindians and more recent colonists. For a variety of mostly socioeconomic
and cultural reasons, widespread consumption of yaupon tea ceased by the late 19th century, but the species is widely used
in ornamental horticulture. Given the environmental damage associated with other caffeine crops, we believe that disuse of
this species is unfortunate, and we report on traits that consumers may consider valuable. We found that total foliar biomass,
caffeine, and antioxidant production all increased with nitrogen fertilization in one common ornamental yaupon cultivar, ‘Nana.’
Increasing light availability was associated with increased antioxidant activity but not with the decreased caffeine production
predicted by the carbon/nutrient balance hypothesis for secondary metabolite production. We also found the highest caffeine
concentrations in another yaupon cultivar, ‘Pendula,’ but suggest that the wide range of chemical variation offered by wild-type
yaupon populations renders them more suitable as sources for the development of high caffeine-producing varieties. The results
of this study suggest that yaupon is a viable caffeine alternative for North Americans living within its range on the southeastern
coastal plain. 相似文献
13.
M. T. McHenry B. R. Wilson J. M. Lemon D. E. Donnelly I. G. Growns 《Plant and Soil》2006,285(1-2):245-255
Dense White Cypress Pine (Callitris glaucophylla J. Thompson and L.A.S. Johnson) regrowth occurs frequently across previously cleared landscapes in New South Wales (NSW), and is thought to adversely affect agricultural production and to cause land degradation. The NSW Native Vegetation Act (2003) requires that management of native vegetation including pre-1990 regrowth must ‘improve or maintain’ site condition, yet there is currently limited information regarding techniques for the optimum management of C. glaucophylla in this regard. We conducted a preliminary study to examine floristic composition, soil condition (to 50 cm) and carbon storage under ‘Dense’ (dense regrowth), ‘Thinned’ (dense regrowth thinned 2000/2001) and ‘Un-colonised’ (pasture not yet recolonised by C.␣glaucophylla) plots on private lands in NSW. Reduced tree density from thinning resulted in increased biomass of the remaining individual trees. Un-colonised plots had significantly more groundcover than thinned plots, which had significantly more groundcover than dense plots. Differences in plant diversity however, were explained by site factors rather than land use. Soils in the dense plots were the most acid but soil pH was significantly higher in thinned plots and pH was highest in soil of the un-colonised plots. Mean values for carbon, nitrogen, sulphur and extractable phosphorus varied among sites, although each were significantly more abundant in the mineral soil of dense and thinned plots compared with un-colonised plots, suggesting that thinning had had a minimal effect on the soil parameters assessed. Accounting for all site components, site carbon storage was significantly higher in dense and thinned plots compared with un-colonised plots due to elevated levels of soil and litter carbon as well as the presence of trees. The results indicate that thinning dense C. glaucophylla can maintain and (by some measures) improve site condition. However, given the variability in some of the parameters assessed, further study across a wider range of soil types and rainfall gradients is proposed. 相似文献
14.
As part of a program to develop starter cultures aiding in the spoilage control and sanitation of African fermented foods,
a cereal-based food (‘ogi’ and its solid form ‘agidi’ or ‘eko’) was prepared using a bacteriocin-producingLactobacillus strain as the starter culture. The survival of an enterotoxigenicEscherichia coli strain was investigated in the naturally fermented food and in food fermented with the starter bacteriocin-producingLactobacillus strain. An inhibition ofE. coli was observed within 2 h of incubation in ‘ogi’ fermented with the bacteriocin producing strain. After 6 h, the viable count
ofE. coli in locally fermented ‘ogi’ was log 6.41 (2.54×106CFU/mL), whereas in ‘ogi’ fermented with the bacteriocin producer it was reduced to log 1.70 (0.5×102 CFU/mL). Comparison of the shelf life of ‘agidi’ prepared from the naturally fermented food with that fermented with the
bacteriocin-producing starter culture showed that the latter had a better shelf life (kept for 11 d before spoilage occurred
as compared with 7 d for the natural one). The results are discussed in terms of the potential of bacteriocin-producing cultures
in the control and retardation of spoilage and food-forne infections in some African fermented foods. 相似文献
15.
Yves Hingrat Michel Saint Jalme Frédéric Ysnel Eric Le Nuz Frédéric Lacroix 《Journal of Ornithology》2007,148(1):39-52
Studies of the movements and home-ranges of houbara bustards (Chlamydotis undulata undulata) showed sexual and seasonal differences in the use of space, with a polygynous mating system similar to an ‘exploded-lek’
or a ‘resource-defence-polygyny’, that remains undefined. We used the arthropod biomass as an index of the trophic quality
of six defined habitats and we radio-tracked 7 females and 13 males to test whether sexual and seasonal variations in habitat
use were related to resource availability, and to verify if critical resources for breeding females were monopolised by males.
We analysed habitat selection in both sexes separately. We used the habitat type composition of buffer zones around radio-locations
to study annual and seasonal habitat selection and to identify preferred habitats, using the chi-square goodness-of-fit test.
Habitat use between sexes and between seasons were compared using MANOVA based on log-ratios of habitat proportions. During
the year, and in each season, both sexes appeared to be significantly selective for habitats in comparison to their availability.
But males avoided esparto grass, while females used all habitats. Habitat use differed between sexes in the breeding season,
but not in the non-breeding season. In spring, when food resources were abundant and uniformly distributed in space, males
preferred ‘temporarily flooded areas’ and females preferred ‘reg with tall perennials’ that offered both food and cover for
brooding. Critical resources were not monopolised by males and the mating system fulfilled the definition of the ‘exploded-lek’.
Leks are key sites for reproduction and should be considered as priority areas in further conservation plans. 相似文献
16.
Fourteen of 200Lactobacillus isolates from African fermented foods,viz. ‘wara’, ‘kenkey’, ‘ugba’, ‘ogi’, ‘kunuzarki’, ‘fufu’ and ‘iru’ were found to produce bacteriocins againstL. plantarum and only three bacteriocinogenic isolates inhibited some of the food pathogens. Plasmid analysis of the 14 bacteriocin-producing
lactobacilli showed that only 5 isolates harbored plasmids ranging in size from 3.1 to 55.5 kb. 相似文献
17.
Kristine M. Averill David A. Mortensen Erica A. H. Smithwick Eric Post 《Biological invasions》2016,18(5):1247-1263
Native generalist herbivores might limit plant invasion by consuming invading plants or enhance plant invasion by selectively avoiding them. The role of herbivores in plant invasion has been investigated in relation to plant native/introduced status, however, a knowledge gap exists about whether food selection occurs according to native/introduced status or to species. We tested preference of the native herbivore white-tailed deer (Odocoileus virginianus) for widespread and frequently occurring invasive introduced and native plants in the northeastern United States. Multiple-choice deer preference trials were conducted for the species and relative preference was determined using biomass consumption and feeding behavior. While more native than introduced plant biomass was consumed overall, deer food selection varied strongly by plant species. Results show consistent deer avoidance of several invasive introduced plants (Alliaria petiolata, Berberis thunbergii, and Microstegium vimineum) and a native plant (Dennstaedtia punctilobula). Other invasive introduced plants (Celastrus orbiculatus, Ligustrum vulgare, and Lonicera morrowii) and a native plant (Acer rubrum) were highly preferred. These results provide evidence that herbivore impacts on plant invaders depend on plant species palatability. Consequently, herbivore selectivity likely plays an important role in the invasion process. To the extent that herbivory impacts population demographics, these results suggest that native generalist herbivores promote enemy release of some plant invaders by avoiding them and contribute to biotic resistance of others by consuming them. 相似文献
18.
Relationships between soil invertebrate populations and primary production of a tallgrass prairie were investigated using the insecticide-nematicide carbofuran and a range of mowing intensities to manipulate invertebrate densities and resource quantity and quality. The trophic composition of nematode populations was monitored through each of two growing seasons. Earthworm and macroarthropod densities and primary production were assessed at the end of the second season. Invertebrate densities were generally reduced in carbofuran-treated plots, although individual weights of surviving macroarth-ropod herbivores increased significantly (p<0.05). Carbofuran failed to affect estimates of above- or belowground plant biomass after two years of treatment. Changes in resource quantity and quality resulted in rapid responses by dominant invertebrate consumer populations. A 28% reduction in live root mass and a 24% increase in root detritus following two years of mowing was associated with a 54% decrease in herbivorous nematode densities, a 47% increase in microbivorous nematode densities, and a 41% increase in native earthworm biomass. 相似文献
19.
R. H. Marrs M. G. Le Duc S. M. Smart K. J. Kirby R. G. H. Bunce P. M. Corney 《Kew Bulletin》2010,65(4):583-594
The invasion of native habitats by exotic, or alien, plant species has received considerable attention recently from policy,
research, and practical conservation management perspectives. However, a new hypothesis for species dynamics in Britain suggests
that a small number of aggressive native plant species (termed ‘thugs’) may have an equal, or greater, impact on native species
and habitats than exotic species. Here, we examine this hypothesis using multivariate techniques with field-layer cover data
collected during a country-wide survey of British woodlands. Multivariate analysis of these data identified a north-south
gradient on the first axis, and that 20 of the 25 National Vegetation Classification woodland types were sampled within the
study. The most abundant field-layer species included three of the proposed native ‘thugs’, i.e. Rubus fruticosus, Pteridium aquilinum and Hedera helix in addition to the native woodland indicator species Mercurialis perennis. Variation partitioning was used to compare the relative importance of native field-layer ‘thug’ species with invading alien
shrub and tree species relative to other environmental drivers. The variation in the field-layer data-set explained by the
three native ‘thug’ species was significant, but they explained a relatively small proportion of the variation relative to
other environmental variables (climate, soil, management factors etc.). They did, however, explain almost four times as much
variation as the three alien species that were significantly correlated with field-layer species composition (Acer pseudoplatanus, Impatiens glandulifera, Rhododendron ponticum). The results of this analysis suggest that the field-layer of British woodlands is impacted as much by native ‘thug’ species,
as it is from ‘aliens’. Concern about the impact of these native ‘thug’ species has been reported previously, but their impact
has not previously been compared to the impact of invading aliens. It is hoped that this analysis will do two things, first
to act as a sound baseline for assessing any changing balance that should occur in the future, and second, to prompt both
ecologists and conservationists to develop woodland management policies based on sound science. 相似文献
20.
The accidental introduction of the spiralling whitefly, Aleurodicus dispersus Russell (Homoptera: Aleyrodidae) to Seychelles in late 2003 is exploited during early 2005 to study interactions between
A. dispersus, native and exotic host plants and their associated arthropod fauna. The numbers of A. dispersus egg spirals and pupae, predator and herbivore taxa were recorded for eight related native/exotic pairs of host plants found
on Mahé, the largest island in Seychelles. Our data revealed no significant difference in herbivore density (excluding A. dispersus) between related native and exotic plants, which suggests that the exotic plants do not benefit from ‘enemy release’. There
were also no differences in predator density, or combined species richness between native and exotic plants. Together these
data suggest that ‘biotic resistance’ to invasion is also unlikely. Despite the apparent lack of differences in community
structure significantly fewer A. dispersus egg spirals and pupae were found on the native plants than on the exotic plants. Additional data on A. dispersus density were collected on Cousin Island, a managed nature reserve in which exotic plants are carefully controlled. Significantly
higher densities of A. dispersus were observed on Mahé, where exotic plants are abundant, than on Cousin. These data suggest that the rapid invasion of Seychelles
by A. dispersus may largely be due to the high proportion of plant species that are both exotic and hosts of A. dispersus; no support was found for either the ‘enemy release’ or the ‘biotic resistance’ hypotheses. 相似文献