Do native predators benefit from non‐native prey?

Despite knowledge on invasive species’ predatory effects, we know little of their influence as prey. Non‐native prey should have a neutral to positive effect on native predators by supplementing the prey base. However, if non‐native prey displace native prey, then an invader's net influence should depend on both its abundance and value relative to native prey. We conducted a meta‐analysis to quantify the effect of non‐native prey on native predator populations. Relative to native prey, non‐native prey similarly or negatively affect native predators, but only when studies employed a substitutive design that examined the effects of each prey species in isolation from other prey. When native predators had access to non‐native and native prey simultaneously, predator abundance increased significantly relative to pre‐invasion abundance. Although non‐native prey may have a lower per capita value than native prey, they seem to benefit native predators by serving as a supplemental prey resource.     

Can replacement of native by non‐native trout alter stream‐riparian food webs?

相似文献   

Invaders interfere with native parasite–host interactions

The introduction of species is of increasing concern as invaders often reduce the abundance of native species due to a variety of interactions like habitat engineering, predation and competition. A more subtle and not recognized effect of invaders on their recipient biota is their potential interference with native parasite–host interactions. Here, we experimentally demonstrate that two invasive molluscan filter-feeders of European coastal waters interfere with the transmission of free-living infective trematode larval stages and hereby mitigate the parasite burden of native mussels (Mytilus edulis). In laboratory mesocosm experiments, the presence of Pacific oysters (Crassostrea gigas) and American slipper limpets (Crepidula fornicata) reduced the parasite load in mussels by 65–77% and 89% in single and mixed species treatments, respectively. Both introduced species acted as decoys for the trematodes thus reducing the risk of hosts to become infected. This dilution effect was density-dependent with higher reductions at higher invader densities. Similar effects in a field experiment with artificial oyster beds suggest the observed dilution effect to be relevant in the field. As parasite infections have detrimental effects on the mussel hosts, the presence of the two invaders may elicit a beneficial effect on mussels. Our experiments indicate that introduced species alter native parasite–hosts systems thus extending the potential impacts of invaders beyond the usually perceived mechanisms.     

The influence of a native tree species mix component on bird communities in non‐native coniferous plantations in Ireland

Capsule Norway Spruce plantations with Scots Pine as a secondary tree species had higher bird densities than pure Norway Spruce. Shrub cover was the most important structural variable, influencing bird density, species richness and Simpson’s diversity.

Aims To investigate whether incorporating a native tree component into non‐native coniferous plantations had any effect on bird communities or vegetation structure.

Methods Birds were surveyed in plantations of Norway Spruce mixed with Oak and Scots Pine, each paired with a plantation of pure Norway Spruce. distance was used to generate bird densities. Bird density, species richness and Simpson’s diversity were compared between each mix type and pure Norway Spruce. glms were used to investigate relationships between structural components of plantations and bird data.

Results Bird communities of mixed plantations differed only slightly in their composition from pure Norway Spruce. Bird density was significantly higher in Scots Pine mixes than in Oak mixes or pure Norway Spruce. Neither species richness nor Simpson’s diversity differed significantly between the plantation types. Some vegetation components differed between the plantations and shrub cover was positively associated with bird density, species richness and Simpson’s diversity. The presence of rides also increased bird density.

Conclusions There is a positive effect on bird communities of including a native tree species in non‐native coniferous plantations, but the magnitude of the effect is small. The influence of shrub cover on birds suggests that forest management may play an important role in determining the utility of plantations for birds. We recommend the establishment of mixed tree species plantations where possible, although, in the case of Oak mixes, the Norway Spruce appeared to suppress growth of the Oak and thus may be restricting its effect on birds. Changes in management, such as planting Oaks in clumps or heavier thinning of the coniferous component, could address this problem.     

Does the recruitment of a non‐native mussel in native eelgrass habitat explain their disjunct adult distributions?

We studied variability in the abundance of small individuals of an invasive mussel (Musculista senhousia) across the depth distribution of a native marine angiosperm, eelgrass (Zostera marina). Adult mussels and eelgrass have a disjunct local distribution, each limiting the other in complex ways. To assess whether eelgrass also influenced the distribution of juvenile mussels, we sampled inside and outside eelgrass beds in one site in Mission Bay and two in San Diego Bay, California, USA. We sampled mussels in size classes 0.26–0.50 mm, 0.51–1.00 mm, 1.10–2.00 mm and > 2.00 mm from September 1997 to April 1999. We also monitored gonad development in larger mussels and in situ growth of mussels ≤ 2 mm tagged with the chemical marker calcein. Spatial and temporal variations in mussel abundances were high but seasonal patterns were roughly similar at San Diego Bay sites; very few mussels were found in Mission Bay. Mussels with full gonads were found year‐round in San Diego Bay, as were mussels in the smallest size class (with a large peak in fall and a smaller secondary one in spring), suggesting that many of the smallest mussels represent recruitment. The observation that most, although not all, tagged mussels increased in size provides further support for recruitment. Some of the highest numbers of mussels in the smallest size class were found inside eelgrass beds, indicating that eelgrass does not restrict and may actually enhance the distribution of very small mussels. The disjunct distribution of adult mussels and eelgrass thus is apparently established primarily postrecruitment. M. senhousia is capable of year‐round reproduction, recruitment and growth, and thus is poised to preempt space from eelgrass following any disturbance that results in eelgrass declines, such as habitat fragmentation, eutrophication, or disease.     

Habitat enhancement and native fish conservation: can enhancement of channel complexity promote the coexistence of native and introduced fishes?

Native fishes worldwide have declined as a consequence of habitat loss and degradation and introduction of non-native species. In response to these declines, river restoration projects have been initiated to enhance habitat and remove introduced fishes; however, non-native fish removal is not always logistically feasible or socially acceptable. Consequently, managers often seek to enhance degraded habitat in such a way that native fishes can coexist with introduced species. We quantified dynamics of fish communities to three newly constructed side channels in the Provo River, Utah, USA, to determine if and how they promoted coexistence between native fishes (nine species) and non-native brown trout (Salmo trutta L.). Native and introduced fishes responded differently in each side channel as a function of the unique characteristics and histories of side channels. Beaver activity in two of the three side channels caused habitat differentiation or channel isolation that facilitated the establishment of native species. The third side channel had greater connectivity to and similar habitat as the main channel of the Provo River, resulting in a similar fish community to main channel habitats (i.e. dominated by brown trout with only a few native fish species). These results demonstrate the importance of understanding habitat preferences for each species in a community to guide habitat enhancement projects and the need to create refuge habitats for native fishes.     

In vitro palmitoylation of native bovine brain G_oα

The native Goα was purified from bovine brain cortex and palmitoylated in vitro. The in vitro palmitoylation site was the same as that in vivo. The internal palmitoylation of purified native Goα was found to be largely maintained. The apparent palmitoylation ratio was significantly increased after the Goα was treated with DTT. The GTPγS binding characteristic of Goα was not influenced by palmitoylation, however, the affinity for LUVs was increased dramatically. The in vitro palmitoylation model of Goα provides a better basis for studying the functional role of G protein palmitoylation in signal transduction.     

Is Histoplasma capsulatum a native inhabitant of Japan?

Histoplasmosis is an infectious disease caused by inhaling spores of the fungal pathogen H. capsulatum and in Japan is considered an imported mycosis. However, some patients in Japan with histoplasmosis have no history of traveling overseas nor of risk of occupational exposure to Histoplasma. To investigate the possibility of native distribution of Histoplasma in Japan, 187 bat guano samples from 67 bat‐inhabited caves in 17 prefectures were collected. These were examined for H. capsulatum by culture and Histoplasma‐specific PCR in three independent laboratories. No H. capsulatum was detected by either method, therefore H. capsulatum is unlikely to be present in bat guano in Japanese caves.     

Does detritus quality predict the effect of native and non‐native plants on the performance of larval amphibians?

1. The lack of consistent differences between the traits of native and non‐native plant species makes it difficult to make general predictions about the ecological impact of invasive plants; however, the increasing number of non‐native plants in many habitats makes the assessment of the impact of each individual species impracticable. General knowledge about how specific plant traits are linked to their effects on communities or ecosystems may be more useful for predicting the effect of plant invasions. Specifically, we hypothesised that higher carbon‐to‐nitrogen ratio (C:N) and percent lignin in plant detritus would reduce the rate of development and total mass at metamorphosis of tadpoles, resulting in lower metamorph production (total fresh biomass) and amphibian species richness. 2. To test these hypotheses, we raised five species of tadpoles in mesocosms containing senescent leaves of three common native and three common non‐native wetland plants that varied in C:N ratio and % lignin. 3. Leaf mass loss, total metamorph production and the number of species that metamorphosed declined as a function of increasing C:N ratio of plant leaves. Plant lignin content was not related to the production of metamorphs or the number of species that metamorphosed. The percentage of wood frog (Lithobates sylvaticus) and American toad (Anaxyrus americanus) tadpoles reaching metamorphosis declined as a function of increasing plant C:N ratio. Mean time to metamorphosis increased and mean mass at metamorphosis declined as a function of increasing plant C:N ratio. Tadpole performance and metamorph diversity and production (biomass) were similar between native and non‐native plant species with similar C:N ratio in leaves. Percent lignin was not a significant predictor of tadpole performance. 4. Our results show that the impact of a plant invasion on tadpole performance could depend on differences between the quality of the detritus produced by the invading species and that of the native species it replaces. We suggest that plant community changes that lead to dominance by more recalcitrant plant species (those with higher leaf C:N ratio) may negatively affect amphibian populations.     

Non‐native conditions favor non‐native populations of invasive plant: demographic consequences of seed size variation?

Trait differences between native and non‐native populations may explain the greater abundance and impact of some organisms in their non‐native ranges than in their native ranges. Here, we conducted reciprocal common gardens in southwestern Turkey (home) and central Argentina (away) to explore the hypothesis that the greater success of the invasive ruderal Centaurea solstitialis in Argentina than Turkey is partially explained by differences between home and away populations. Unusual among common gardens, our experimental design included seed additions to explicitly evaluate population level responses, as well as disturbance and no‐disturbance treatments. We documented seed mass in native and non‐native populations, and during the experiment, we periodically measured density, plant size, and herbivory. After six months, we determined the establishment of plants for populations from both origins in both home and away common gardens. Seed mass was two times larger for Argentinean than Turkish populations. Density, plant size and final establishment were also greater for plants from Argentinean than from Turkish populations, but only in the common garden in Argentina. In Turkey, no differences between population origins were detected for these variables. Herbivory was similar for populations from both origins in both common gardens. As expected, disturbance generally increased plant performance in both regions. Our results suggest that increased seed size in non‐native populations may have demographic consequences under non‐native conditions that can contribute to the invasive success of C. solstitialis. This is the first reciprocal common garden that supports the idea that seed size variation contributes to demographic differences for an invasive species between native and non‐native distributions, but our findings further suggest that seed size effects on demography depend on the ecological context in which population processes occur.     

Invasion by Rattus rattus into native coastal forests of south‐eastern Australia: are native small mammals at risk?

The black rat, Rattus rattus, is an alien rodent in Australian ecosystems where niche overlap with native small mammals may lead to competition for resources and displacement of native species. In coastal habitats surrounding Jervis Bay in south‐eastern Australia, R. rattus co‐occurs with the native bush rat, Rattus fuscipes, and brown antechinus, Antechinus stuartii. Relative distributions and abundances, and fine‐scale space use suggest invasive and native rodents compete for use of space and habitat. Such competitive interactions were not evident between R. rattus and native A. stuartii, which was negatively influenced more by disturbance to habitat. Differences in rodent communities between spatially separate forests forming the northern and southern peninsulas of Jervis Bay potentially reflect symmetrical competition and differences in competitive outcomes. In southern forests, R. rattus was largely restricted to patches of disturbed forest associated with campgrounds. Competitive interference by native rodent populations inhabiting surrounding intact forests may have so far limited R. rattus colonization of these areas. In northern forests, R. rattus was the predominant rodent irrespective of disturbance, while populations of R. fuscipes were unusually low seemingly due to poor juvenile recruitment. Native individuals avoided areas frequented by adult R. rattus and given that species did not partition use of microhabitats, R. rattus most likely precluded R. fuscipes from suitable habitat and in doing so limited native populations. We discuss how natural disturbance of habitat and human activity have potentially facilitated successful invasion by R. rattus of the northern forests. Studies that manipulate rodent populations are required to support these interpretations of observed patterns.     

What should the Z-score of native protein structures be?

The Z-score of a protein is defined as the energy separation between the native fold and the average of an ensemble of misfolds in the units of the standard deviation of the ensemble. The Z-score is often used as a way of testing the knowledge-based potentials for their ability to recognize the native fold from other alternatives. However, it is not known what range of values the Z-scores should have if one had a correct potential. Here, we offer an estimate of Z-scores extracted from calorimetric measurements of proteins. The energies obtained from these experimental data are compared with those from computer simulations of a lattice model protein. It is suggested that the Z-scores calculated from different knowledge-based potentials are generally too small in comparison with the experimental values.     

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.     

Phormium tenax—New Zealand’s native hard fiber

This large iris-like plant yields a hard fiber which has been important in New Zealand’s past export trade. Today the total native annual production of about 5,000 long tons is wholly utilized domestically and provides only 15 percent of New Zealand’s fiber requirements for use in woolpacks, matting, twine and other articles. Imported fibers, such as sisal, jute and hemp, make up the difference.     

Soil mycoflora from trufflè native areas of Saudi Arabia

Soil fungi of areas in the North-Eastern region of Saudi Arabia where truffles are native were surveyed. Forty-three species of fungi belonging to twenty genera were isolated. Most were recovered from soils underneath or around truffle ascocarps: thirty species from soil under the surface of Tirmania nivea ascocarps, twenty-four from Terfezia boudieri soil and twenty species each from Tirmania pinoyi and Terfezia claveryi soils. Rhizosphere soil of Helianthemum lippi, on the other hand, yielded twenty-four fungal species while only fourteen fungal species were found in soil without vegetation. The total counts of fungi/g soil were highest in soils from the under surface of truffles, followed by rhizosphere soil, with the lowest in soils without vegetation.