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.     

Non‐native flora of Italy: Species distribution and threats

Abstract

In this paper, we provide an overview of the distribution and invasive status of non‐native species in the Italian flora across its administrative regions, biogeographic regions and main land use types, and a synthesis of current knowledge on the threats they pose within the country. The information on non‐native plant species collected during the project “A survey of the non‐native Italian flora” was used to compile comprehensive regional and national databases. The number of non‐native species within a given administrative region increases in proportion to its size, resident population density and latitude, reaching the highest values in the intensively cultivated, heavily industrialized and urbanized Po Plain in northern Italy. The number of casual species is positively correlated with the number of yearly visitors in each region and negatively correlated with the proportion of mountainous terrain within the region. If compared with the Continental and Mediterranean biogeographic regions, the Alpine region yields the lowest number of non‐native species and lowest proportion of casual species. The number and density of introduced species is highest in artificial land use types, particularly in urban areas. A negative impact is reported to be exerted by 203 species, most of which are agricultural weeds.     

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.     

Spectroscopic characterization of the inclusion complexes of luteolin with native and derivatized β-cyclodextrin

The inclusion complexes of Luteolin (LU) with cyclodextrins (CDs) including β-cyclodextrin (βCD), hydroxypropyl-β-cyclodextrin (HPβCD) and dimethyl-β-cyclodextrin (DMβCD), Scheme 1, have been investigated using the method of steady-state fluorescence. The stoichiometric ratio of the three complexes was found to be 1:1 and the stability constants (K) were estimated from spectrofluorometric titrations, as well as the thermodynamic parameters. Maximum inclusion ability was obtained in the case of HPβCD followed by DMβCD and βCD. Moreover, ¹H NMR and 2D NMR were carried out, revealing that LU has different form of inclusion which is in agreement with molecular modeling studies. These models confirm that when LU–βCD and LU–DMβCD complexes are formed, the B-ring is oriented toward the primary rim; however, for LU–HPβCD complex this ring is oriented toward the secondary rim. The ESR results showed that the antioxidant activity of luteolin was the order LU–HPβCD > LU–DMβCD > LU–βCD > LU, hence the LU-complexes behave are better antioxidants than luteolin free.     

Do heat and smoke increase emergence of exotic and native plants in the matorral of central Chile?

We studied the effect of heat shock and wood-fueled smoke on the emergence of native and exotic plant species in soil samples obtained in an evergreen shrubland of central Chile, located on the eastern foothills of the Coastal Range of Lampa. Immediately after collection samples were dried and stored under laboratory condition. For each two transect, 10 samples were randomly chosen, and one of the following treatments was applied: 1) Heat-shock treatment. 2) Plant-produced smoke treatment. 3) Combined heat-and-smoke treatment. 4) Control, corresponding to samples not subjected to treatment. Twenty-three species, representing 12 families, emerged from the soil samples. The best-represented families were Poaceae and Asteraceae. All of the emerged species were herbs, 21 were annuals, and 14 were exotic to Chile. Fire-related triggers used in this study did not increase the emergence and/or abundance of exotic species with respect to natives in soil samples. Interestingly, this study provides evidence that heat-shock can increase the emergence of native herbs.     

Are native and non‐native pollinator friendly plants equally valuable for native wild bee communities?

Bees rely on floral pollen and nectar for food. Therefore, pollinator friendly plantings are often used to enrich habitats in bee conservation efforts. As part of these plantings, non‐native plants may provide valuable floral resources, but their effects on native bee communities have not been assessed in direct comparison with native pollinator friendly plantings. In this study, we performed a common garden experiment by seeding mixes of 20 native and 20 non‐native pollinator friendly plant species at separate neighboring plots at three sites in Maryland, USA, and recorded flower visitors for 2 years. A total of 3,744 bees (120 species) were collected. Bee abundance and species richness were either similar across plant types (midseason and for abundance also late season) or lower at native than at non‐native plots (early season and for richness also late season). The overall bee community composition differed significantly between native and non‐native plots, with 11 and 23 bee species being found exclusively at one plot type or the other, respectively. Additionally, some species were more abundant at native plant plots, while others were more abundant at non‐natives. Native plants hosted more specialized plant–bee visitation networks than non‐native plants. Three species out of the five most abundant bee species were more specialized when foraging on native plants than on non‐native plants. Overall, visitation networks were more specialized in the early season than in late seasons. Our findings suggest that non‐native plants can benefit native pollinators, but may alter foraging patterns, bee community assemblage, and bee–plant network structures.     

An investigation of the action of porcine pancreatic α-amylase on native and gelatinised starches

The action of pancreatic α-amylase (EC 3.2.1.1) on various starches has been studied in order to achieve better understanding of how starch structural properties influence enzyme kinetic parameters. Such studies are important in seeking explanations for the wide differences reported in postprandial glycaemic and insulinaemic indices associated with different starchy foodstuffs. Using starches from a number of different sources, in both native and gelatinised forms, as substrates for porcine α-amylase, we showed by enzyme kinetic studies that adsorption of amylase to starch is of kinetic importance in the reaction mechanism, so that the relationship between reaction velocity and enzyme concentration [E₀] is logarithmic and described by the Freundlich equation. Estimations of catalytic efficiencies were derived from measurements of k_cat/K_m performed with constant enzyme concentration so that comparisons between different starches were not complicated by the logarithmic relationship between E₀ and reaction velocity. Such studies reveal that native starches from normal and waxy rice are slightly better substrates than those from wheat and potato. After gelatinisation at 100°C, k_cat/K_m values increased by 13-fold (waxy rice) to 239-fold (potato). Phosphate present in potato starch may aid the swelling process during heating of suspensions; this seems to produce a very favourable substrate for the enzyme. Investigation of pre-heat treatment effects on wheat starch shows that the relationship between treatment and k_cat/K_m is not a simple one. The value of k_cat/K_m rises to reach a maximum at a pre-treatment temperature of 75°C and then falls sharply if the treatment is conducted at higher temperatures. It is known that amylose is leached from starch granules during heating and dissolves. On cooling, the dissolved starch is likely to retrograde and become resistant to amylolysis. Thus the catalytic efficiency tends to fall. In addition, we find that the catalytic efficiency on the different starches varies inversely with their solubility and we interpret this finding on the assumption that the greater the solubility, the greater is the likelihood of retrogradation. We conclude that although α-amylase is present in high activity in digestive fluid, the enzymic hydrolysis of starch may be a limiting factor in carbohydrate digestion because of factors related to the physico-chemical properties of starchy foods.     

Do associations between native and invasive plants provide signals of invasive impacts?

Do invasive plant species act more as “passengers” or drivers of ecological change in native plant communities? Snapshot studies based on correlations at the site scale ignore longer-term dynamics and variation in how particular invaders affect particular native species. We analyzed patterns of co-occurrence between three invading species (Alliaria petiolata, Lonicera x bella, and Rhamnus cathartica) and 70 native plant species in 94 southern Wisconsin forests at two scales to test four hypotheses. Surveys at these sites in the 1950s and again in the 2000s allowed us to assess how initial plant diversity and site conditions affected subsequent patterns of invasion. Sites with more native species in the 1950s experienced fewer invasions of Lonicera and Rhamnus. However, this result may reflect the fact that more fragmented habitat patches supported both fewer species in the 1950s and more invasions. At the site-level, few negative correlations exist between invasive and native species’ abundances. Sites with higher Alliaria densities in the 2000s, however, support fewer native species and lower populations of several declining natives. Rhamnus-invaded sites support lower populations of two increasing species. Association (C-score) analyses detect more associations and more negative associations at the 1 m² scale than at the site scale. Most strong associations between invasive and increasing native species are positive while those with declining natives are often negative. Species restricted to specialized habitats rarely co-occur with invaders. Alliaria has more negative associations at fragmented sites where it is more abundant and invasions may be older. Fine-scale invasive-native associations were stronger, easier to detect, and less consistent than those detectable at the site-level. Thus, screening large numbers of local associations using observational data may allow us to identify particular invasive-native interactions worth further investigation. Although invading plants sometimes act as passive passengers, increasing in tandem with certain native plants in response to disturbed fragmented habitats, they may also contribute to the declines we observe in many native species. Monitoring invasions would allow us to assess whether local associations serve to predict subsequent invasive species impacts.     

Colilargo’s occupancy and the role of native and exotic plants in hantavirus expansion and transmission risk

Mammal Research - In this work, we examined the relationship of Oligoryzomys longicaudatus’ (the Andes virus [ANDV] host, commonly known as the colilargo) occupancy and the cover of dominant...     

Nature of thermal transitions of native and acid-hydrolysed pea starch: Does gelatinization really happen?

Thermal transitions of native and acid-hydrolysed starch were investigated for the first time by employing differential scanning calorimetry (DSC) in combination with field emission scanning electron microscopy (FE-SEM) to examine morphological changes in the starch after hydrothermal treatment in the DSC pans. The characteristic, well-defined endothermic transition was observed in the DSC traces for native starch and starch after one day of acid hydrolysis, but after two days of hydrolysis the endothermic transition became broad and undefined. After heating in DSC pans, native starch was observed visually and with SEM to have formed a gel, whereas starch granules hydrolysed for one day appeared to have undergone only limited swelling and coalescence. Starch that had been hydrolysed for two or more days appeared powdery and SEM images revealed that the granules had undergone very little swelling. The thermal transitions of native and acid-hydrolysed starch are interpreted in terms of the theory of polymer swelling and dissolution. Native granules and granules with only minimal acid damage are able to swell within the constraints of the water-limited conditions of DSC, but as acid hydrolysis progresses the capacity of the granules to swell is decreased and endothermic transitions are increasingly due to dissolution of polymer chains. An exothermic transition that followed the main endothermic transition is proposed to be due to the condensation of water vapour on the lid of the DSC pan.     

Immigrant and native? The case of the swamp foxtail Cenchrus purpurascens in Australia

Aim

Spring wetlands in arid regions of Australia provide habitat for many highly endemic organisms, including fish, molluscs, crustaceans and plants, but these unique ecosystems have been under pressure since the arrival of Europeans about 250 years ago. Arguments over whether particular plant species are long‐term spring inhabitants or recent immigrants are confounding efforts to conserve spring flora. One such example is the swamp foxtail, Cenchrus purpurascens, a grass that is variably listed in the literature as being native to Australian wetlands or as being an introduced weedy species from Asia.

Location

Australia, China and Korea.

Methods

We use DNA sequences of the nuclear ITS and the chloroplast DNA regions trnL‐F and matK, complemented with newly designed simple sequence repeat (SSR) markers, to assess the native status of C. purpurascens in Australia and determine whether there is genetic differentiation among spring populations.

Results

We find that, although there has been gene flow between Asia and Australia in the geological past, the populations are now strongly differentiated: C. purpurascens has probably been present in Australia through the Pleistocene. In Australia, there is also strong genetic differentiation among populations from different springs, and between springs and non‐springs populations, indicating long‐term occupancy of some springs sites.

Main conclusions

Cenchrus purpurascens was present in Australia well before European colonization of the continent. The level of genetic differentiation among populations enhances the existing conservation values of Elizabeth Springs, Edgbaston, Doongmabulla and Carnarvon Gorge springs complexes within the Great Artesian Basin.

     

Will a warmer and wetter future cause extinction of native Hawaiian forest birds?

Isolation of the Hawaiian archipelago produced a highly endemic and unique avifauna. Avian malaria (Plasmodium relictum), an introduced mosquito‐borne pathogen, is a primary cause of extinctions and declines of these endemic honeycreepers. Our research assesses how global climate change will affect future malaria risk and native bird populations. We used an epidemiological model to evaluate future bird–mosquito–malaria dynamics in response to alternative climate projections from the Coupled Model Intercomparison Project. Climate changes during the second half of the century accelerate malaria transmission and cause a dramatic decline in bird abundance. Different temperature and precipitation patterns produce divergent trajectories where native birds persist with low malaria infection under a warmer and dryer projection (RCP4.5), but suffer high malaria infection and severe reductions under hot and dry (RCP8.5) or warm and wet (A1B) futures. We conclude that future global climate change will cause significant decreases in the abundance and diversity of remaining Hawaiian bird communities. Because these effects appear unlikely before mid‐century, natural resource managers have time to implement conservation strategies to protect this unique avifauna from further decimation. Similar climatic drivers for avian and human malaria suggest that mitigation strategies for Hawai'i have broad application to human health.     

Plant–soil feedback of native and range-expanding plant species is insensitive to temperature

Temperature change affects many aboveground and belowground ecosystem processes. Here we investigate the effect of a 5°C temperature increase on plant–soil feedback. We compare plant species from a temperate climate region with immigrant plants that originate from warmer regions and have recently shifted their range polewards. We tested whether the magnitude of plant–soil feedback is affected by ambient temperature and whether the effect of temperature differs between these groups of plant species. Six European/Eurasian plant species that recently colonized the Netherlands (non-natives), and six related species (natives) from the Netherlands were selected. Plant–soil feedback of these species was determined by comparing performance in conspecific and heterospecific soils. In order to test the effect of temperature on these plant–soil feedback interactions, the experiments were performed at two greenhouse temperatures of 20/15°C and 25/20°C, respectively. Inoculation with unconditioned soil had the same effect on natives and non-natives. However, the effect of conspecific conditioned soil was negative compared to heterospecific soil for natives, but was positive for non-natives. In both cases, plant–soil interactions were not affected by temperature. Therefore, we conclude that the temperature component of climate change does not affect the direction, or strength of plant–soil feedback, neither for native nor for non-native plant species. However, as the non-natives have a more positive soil feedback than natives, climate warming may introduce new plant species in temperate regions that have less soil-borne control of abundance.     

Are bottlenecks associated with colonization? Genetic diversity and diapause variation of native and introduced Rhagoletis completa populations

The success of invasive species appears to be a paradox: despite experiencing strong population bottlenecks, invasive species are able to successfully establish in new environments. We studied how the walnut husk fly, Rhagoletis completa, was able to successfully colonize California from the Midwestern United States, by examining genetic diversity and diapause variation of native and introduced fly populations. Climate plays an important role in the successful establishment of introduced insects, because insect diapause is highly dependent upon external climatic conditions. We examined if: (1) fly populations show signs of a population bottleneck, (2) native and introduced flies differ in diapause length when exposed to California and Midwestern climatic conditions, and (3) population genetic diversity is related to variation in diapause length. We assessed if fly diapause conformed more to a model of establishment by local adaptation or to a model of a highly plastic “general-purpose genotype”. Our results indicate that only two populations close to the original introduced location showed signs of a population bottleneck, and native and introduced populations did not differ in genetic diversity. Genetic diversity increased in the northern introduced populations, suggesting that multiple introductions have occurred. Flies emerged about 2 weeks earlier under the Midwestern treatment than the California treatment, and introduced flies emerged about a week earlier than native flies. All flies emerged when walnuts are typically available in California. Although variance in diapause length differed between populations, it did not vary between populations or regions. Furthermore, genetic diversity was not associated with diapause variation. Therefore, multiple introductions and a “general-purpose genotype” appear to have facilitated the fly’s invasion into California.     

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.     

Active-site modification of native and mutant forms of inosine 5′-monophosphate dehydrogenase from Escherichia coli K12

IMP dehydrogenase of Escherichia coli was irreversibly inactivated by Cl-IMP (6-chloro-9-beta-d-ribofuranosylpurine 5'-phosphate, 6-chloropurine ribotide). The inactivation reaction showed saturation kinetics. 6-Chloropurine riboside did not inactivate the enzyme. Inactivation by Cl-IMP was retarded by ligands that bind at the IMP-binding site. Their effectiveness was IMP>XMP>GMP>AMP. NAD(+) did not protect the enzyme from modification. Inactivation of IMP dehydrogenase was accompanied by a change in lambda(max.) of Cl-IMP from 263 to 290nm, indicating formation of a 6-alkylmercaptopurine nucleotide. The spectrum of 6-chloropurine riboside was not changed by IMP dehydrogenase. With excess Cl-IMP the increase in A(290) with time was first-order. Thus it appears that Cl-IMP reacts with only one species of thiol at the IMP-binding site of the enzyme: 2-3mol of Cl-IMP were bound per mol of IMP dehydrogenase tetramer. Of ten mutant enzymes from guaB strains, six reacted with Cl-IMP at a rate similar to that for the native enzyme. The interaction was retarded by IMP. None of the mutant enzymes reacted with 6-chloropurine riboside. 5,5'-Dithiobis-(2-nitrobenzoic acid), iodoacetate, iodoacetamide and methyl methanethiosulphonate also inactivated IMP dehydrogenase. Reduced glutathione re-activated the methanethiolated enzyme, and 2-mercaptoethanol re-activated the enzyme modified by Cl-IMP. IMP did not affect the rate of re-activation of methanethiolated enzyme. Protective modification indicates that Cl-IMP, methyl methanethiosulphonate and iodoacetamide react with the same thiol groups in the enzyme. This is also suggested by the low incorporation of iodo[(14)C]acetamide into Cl-IMP-modified enzyme. Hydrolysis of enzyme inactivated by iodo[(14)C]acetamide revealed radioactivity only in S-carboxymethylcysteine. The use of Cl-IMP as a probe for the IMP-binding site of enzymes from guaB mutants is discussed, together with the possible function of the essential thiol groups.     

Weak or strong invaders? A comparison of impact between the native and invaded ranges of mammals and birds alien to Europe

Aim Species introduced to an area outside of their native range are often thought to have higher impact in this new area. We examined whether this is really the case in mammals and birds and to what extent. In particular, we explored how impacts of alien species vary in relationship to invader identity and type of impact. Location Global. Methods We conducted a thorough review of the literature to compare the impact of alien European mammals and birds in their native and invaded ranges. Based on a series of environmental and economic impact scores, we ordered species along a continuum from weak invaders, which have lower impact in the invaded range, to strong invaders, which have higher impact in the invaded range. Results We found that nearly 80% of the mammals are strong invaders, but only half of the birds. Members of these two classes also affect their communities in different ways; birds more often have an impact via hybridization, whereas mammals have stronger impacts via herbivory, transmission of diseases to wildlife and their effects on agriculture, livestock and forestry. Main conclusions Generally, mammals and birds have different impacts when invading new regions. Although there are some bird species that are strong invaders, these remain the exception among birds, whereas most mammals increase their impact in the invaded range. This study provides a deeper insight into patterns of impact in the invaded range.     

Biotic resistance on coral reefs? Direct and indirect effects of native predators and competitors on invasive lionfish

Coral Reefs - Biotic resistance is the ability of an ecological community to prevent or limit the establishment or success of non-indigenous species. Native species can confer resistance by...