Weed Species Composition in Paddy Field of Usur Town,Bade Local Government,Yobe State,Nigeria

Farmers are eager to know the various types of weeds in paddy fields.This will help in choosing the best weed management practice for effective weed control as well as reducing rice yield losses.The objectives of the study are to identify the weeds species affecting the rice field,to assess the composition of weeds species,to classify the weed species into different families,genera,species,common names,Hausa names,lifecycles,life forms,native/exotic species,propagation and uses,and to determine the dominant weed species.Random vegetation surveys were conducted.Weeds observed were photographed,and prepared as herbarium specimens.Standard key manuals and checklists were utilized for weed identification and later organized using the Angiosperm Phylogeny Group(APG)classification system.A total number of 72 plants species distributed within 16 families and 50 genera were inventoried.The annuals(66.67%)were the dominant weed followed by perennials(33.33%)while biennials were the least.The broad leaves were the dominant weed(44.61%)identified followed by Poaceae(27.7%)and Sedges(11.11%).Results obtained from this study could be useful in choosing the best management practice and in making a decision on the choice of herbicides and directing research towards improved weed control measures.

Assessment of natural regeneration status and diversity of tree species in the biodiversity conservation areas of Northeastern Bangladesh

A study was conducted at two-biodivcrsity conservation areas of Northeastern Bangladesh （a part of Sylhet Forest Division） to assess the species composition, diversity and density of natural regeneration of tree species both indigenous and exotic species. Data were collected by stratified random quadrate method during January 2010 to July 2010. Totally 200 circular plots of 2 m〉〈2 m in size had 5 different habitat types of plants namely; forest, roadside, homestead （surrounding forest dwellers house）, fallow land and others （canals, streams and tea gardens side）, which included a total of 55 regenerating species belonging to 28 families. Meliaceae is the dominant family and shows the highest family importance value （26.3）, having six species, followed by Moraeeae （24.24）. Among the five habitat types, forest （43 species） possess the highes number of species, followed by roadside （23 species）. Total 15 exotic species among 9 families and 40 indigenous species with 24 families were recorded. For exotic species, Tectona grandis possess the highest relative density （11.7%） and relative frequency （10.5%）; Senna siamea had highest relative abundance （7.83%）. In case of indigenous species, Chickrassia tabularis possess the highest relative density （4.23%） and relative frequency （4%）; Dipterocarpus turbinatus bad the highest relative abundance （3.92%）. Tectona grandis （29.66） and Chickrassia tabularis （10.8） had the highest IVI for exotic and indigenous species respectively. Different diversity indic＇es such as Shanon-Winner diversity index,＇ species diversity index, species richness index, species evenness index, Simpson index and species dominance index, etc. were applied to quantify definite diversity. The regeneration of species associated with low levelsof disturbance was in the exotic Species. Study suggests that proper protection from human disturbances and scientific management of natural regeneration of two-study forests may lead a rich biodiversity site in the country.

Intercontinental comparison of phylogenetic relatedness in introduced plants at the transition from naturalization to invasion:A case study on the floras of South Africa and China

Invasive species may pose significant threats to biodiversity and ecosystem structure and functioning.The number of introduced species that have become invasive is substantial and is rapidly increasing.Identifying potentially invasive species and preventing their expansion are of critical importance in invasion ecology.Phylogenetic relatedness between invasive and native species has been used in predicting invasion success.Previous studies on the phylogenetic relatedness of plants at the transition from naturalization to invasion have shown mixed results,which may be because different methods were used in different studies.Here,I use the same method to analyze two comprehensive data sets from South Africa and China,using two phylogenetic metrics reflecting deep and shallow evolutionary histories,to address the question whether the probability of becoming invasive is higher for naturalized species distantly related to the native flora.My study suggests that the probability of becoming invasive is higher for naturalized species closely related to the native flora.The finding of my study is consistent with Darwin's preadaptation hypothesis.

Intensities of human disturbance dictate the floral diversity in tropical forest:the case of a secondary forest in Benguet, Philippines

This study inventoried the floral diversity of a secondary forest in Tuba,Benguet,Philippines as affected by different intensities of human disturbance.This study is unique from other land use studies in Southeast Asia in having conventional farms as the most disturbed land use while other sites have oil palm plantations.A total of 267 species belonging to 222 genera and 78 families was documented.Results showed that the level of human disturbance is the major factor affecting the floral diversity while the effect of elevation is secondary.The level of human disturbance is significantly associated with species richness,species composition,dominant species and biodiversity indices.Greater human disturbance,as in the case of conventional farms,results in lower species richness,predominantly weed composition,dominant weed species and lower biodiversity indices.On the other hand,lesser human disturbance(as in the case of secondary forest)leads to higher species richness,greater native species composition,dominance of indigenous species,and higher diversity indices.The most disturbed land use experienced the greatest loss of species richness,change in floristic composition and vegetation structure,as well as a shift from native to alien-dominated plant communities.These results showed that the effect of land use change is not limited to species richness but also to species composition,dominant species and biodiversity indices.Locally,the study is an important baseline data for biodiversity conservation of the Marcos Highway Watershed Forest Reserve.

Patterns of phylogenetic relatedness of non-native plants across the introduction-naturalization-invasion continuum in China

Human activities have caused the exchange of species among different parts of the world.When introduced species become naturalized and invasive,they may cause great negative impacts on the environment and human societies,and pose significant threats to biodiversity and ecosystem structure.Knowledge on phylogenetic relatedness between native and non-native species and among non-native species at different stages of species invasion may help for better understanding the drivers of species invasion.Here,I analyze a comprehensive data set including both native and non-native angiosperm species in China to determine phylogenetic relatedness of introduced species across a full invasion continuum(from introduction through naturalization to invasion).This study found that(1) introduced plants are a phylogenetically clustered subset of overall(i.e.native plus non-native) angiosperm flora,(2) naturalized plants are a phylogenetically clustered subset of introduced plants,and(3) invasive plants are a phylogenetically clustered subset of naturalized plants.These patterns hold regardless of spatial scales examined(i.e.national versus provincial scale) and whether basal-or tip-weighted metric of phylogenetic relatedness is considered.These findings are consistent with Darwin's preadaptation hypothesis.

Avian malaria,haematocrit,and body condition in invasive wetland passerines settled in southwestern Spain

Avian malaria and related haemosporidian parasites can negatively impact fitness in many songbirds.Research on the malaria infection and its physiological costs on their avian hosts is heavily skewed toward native passerines,with exotic species underrepresented.However,introduced species may carry on and spread new pathogens to native species,and play a role on parasite transmission cycle in invaded bird communities as pathogen reservoir.Here,we molecularly assess the prevalence and diversity of haemosporidian parasites in three introduced wetland passerines(the Red Avadavat Amandava amandava,the Yellow-crowned Bishop Euplectes afer,and the Common Waxbill Estrilda astrild)captured during the same season in southwestern Spain.We also explored the relation between parasite infection,body condition,haematocrit,and uropygial gland volume.We detected an overall parasite prevalence of 3.55%,where Common Waxbills showed higher prevalence(6.94%)than Red Avadavats(1.51%).None Yellow-crowned Bishops were infected with haemosporidians.Almost 60%of infections were caused by Leucocytozoon,and about 40%by Plasmodium.We identified four unique lineages of Plasmodium and three of Leucocytozoon.Moreover,91%of the identified host-parasite interactions represented new host records for these haemosporidian parasites.Parasite infection was not related to body condition,haematocrit,and uropygial gland volume of the wetland passerines.Haematocrit values varied seasonally among bird species.Additionally,haematocrit was positively related to body condition in the Yellow-crowned Bishops,but not in the other species.Red Avadavats had higher haematocrit levels than Yellow-crowned Bishops,whereas Common Waxbills showed the lower haematocrit values.The uropygial gland volume was positively correlated with body condition in all bird species.Common Waxbills showed higher uropygial gland volumes related to their body size than birds from other two species.These outcomes highlight the importance of exotic invasive species in the transmission dynamics of haemosporidian parasites.

Impacts of invasive Iris pseudacorus L.(yellow flag) establishing in an abandoned urban pond on native semi-wetland vegetation

Iris pseudacorus L., intentionally introduced in Japan as an ornamental plant and to improve aquatic environments, has been declared a noxious species in the Invasive Alien Species Act of Japan due to the suspected high ecological risks to the local species and ecosystems. Although prompt responses to I. pseudacorus have been sought to conserve local biodiversity, knowledge about its invasiveness is lacking. Here, we report the relationship between the establishment of I. pseudacorus and floristic changes in semi-wetland vegetation of an abandoned urban pond(Aoike), Nara City, Nara Prepecture, Japan. In total, 64 vascular plants were recorded in the pond, of which 50 were native species, seven were naturalized non-native, and seven were invasive species. On the other hand, most of these vascular plants(42 species) were grassland species and only several aquatic plants(10 species) were found in this study pond. The number of vascular plant species decreased significantly at quadrats with a coverage of I. pseudacorus above 50%. In addition, tendencies of lower number of native species and concomitant higher number of invasive species were found with increasing coverage of I. pseudacorus. From these results, we suggest that it is important to preferentially manage sites where the coverage of I. pseudacorus is above 50%, in order to preserve the local biodiversity. Additionally, as recommended in the literature, it is essential that the cut reproductive organs are kept submerged under deep water for an effective control of I. pseudacorus.

Species richness,phylogenetic diversity and phylogenetic structure patterns of exotic and native plants along an elevational gradient in the Himalaya

Background:So far,macroecological studies in the Himalaya have mostly concentrated on spatial variation of overall species richness along the elevational gradient.Very few studies have attempted to document the diference in elevational richness patterns of native and exotic species.In this study,this knowledge gap is addressed by integrating data on phylogeny and elevational distribution of species to identify the variation in species richness,phylogenetic diversity and phylogenetic structure of exotic and native plant species along an elevational gradient in the Himalaya.Results:Species distribution patterns for exotic and native species difered;exotics tended to show maximum species richness at low elevations while natives tended to predominate at mid-elevations.Native species assemblages showed higher phylogenetic diversity than the exotic species assemblages over the entire elevational gradient in the Himalaya.In terms of phylogenetic structure,exotic species assemblages showed majorly phylogenetic clustering while native species assemblages were characterized by phylogenetic overdispersion over the entire gradient.Conclusions:The fndings of this study indicate that areas with high native species richness and phylogenetic diversity are less receptive to exotic species and vice versa in the Himalaya.Species assemblages with high native phylogenetic overdispersion are less receptive to exotic species than the phylogenetically clustered assemblages.Diferent ecological processes(ecological fltering in case of exotics and resource and niche competition in case of natives)may govern the distribution of exotic and native species along the elevational gradient in the Himalaya.

Characterization of sugar diversity in floral and extra-floral nectar from the Coastal Coral Tree(Erythrina caffra Thunb.)in Southern California

The Coastal Coral Tree (Erythrina caffra Thunb.) produces floral nectar (FN) that serves to attract pollinating insects, but also secretes nectar from extra-floral (EFN) glands that serves to attract predatory insects, such as ants. While studies on myrmecophytes (i.e. specialized plants that attract and interact with ants) have primarily focused on interspecific evaluations of EFN chemistry, the Coastal Coral tree offers an opportunity to contrast intraspecific nectar chemistry with differing evolutionary and ecological functions. We hypothesized that the richness of (molecular) sugar species, relative concentrations, and diversity of sugars in FN and foliar EFN would diverge due to differences in the ecological role of the two types of nectar. High performance liquid chromatography with refractive index detection was used to identify the richness of sugar species (based on retention time), measure the relative concentrations, and evaluate the diversity of sugars in FN and foliar EFN secretions. We detected sugar species unique to each gland type and reported significant differences in the relative concentration of one sugar species common to both gland types. While the mean diversity index of sugars was similar for both gland types, the diversity of foliar EFN sugars was significantly more variable than that of FN sugars. The composition of FN showed little variation, and was reflective of its fundamental role in plant reproduction. Foliar EFN, however, demonstrated the variability expected of a context-dependent myrmecophyte that interacts with a facultative ant species assemblage across a mosaic of abiotic and biotic conditions.

Invasive Spartina alterniflora-induced factors affecting epibenthos distribution in coastal salt marsh, China

Artificially introduced cordgrass, Spartina alterniflora, rapidly colonized the intertidal flats of the Jiangsu coast, eastern China. The epibenthos on an intertidal flat invaded by S. alterniflorawere studied, to identify how local epibenthos species react to an altered environment. Epibenthic samples and surficial sediment samples were collected along a shore-normal profile in 50 quadrats at ten stations across the Spartina salt marsh; and five control quadrats for a station located on the barren sandy-mud flat. The grain size param- eters of the surficial sediments show that S. alterniflora altered the grain size gradient along the profile of the intertidal zone by trapping fine-grained sediments. Spartina alterniflora could inhabit lower elevation- s than indigenous salt marsh vegetation, thus creating larger areas of finer surficial sediments, which was suitable for not only native epibenthic species but also species which do not exist on the barren sandy-mud flat. Correlation analyses show that the epibenthos were sensitive to sediment grain size and type, on the invaded S. alterniflora salt marsh. Further, there was an interspecific relationship affecting the distribution of epibenthos. The results show that epibenthos preferred ecological niches, within the Spartina salt marsh, even in the same sampling station.

Douglas-fir climate sensitivity at two contrasting sites along the southern limit of the European planting range

Douglas-fir(Pseudotsuga menziesii(Mirb.)Franco)is an important exotic tree species that was planted across a large part of Europe during the last century.In both experimental trials and conventional forest plantations,the trees grow at a high rate and produce high-quality timber.The present study investigated climate-growth relationships of Douglas-fi r at two Italian sites that contrast in climate:a Mediterranean area in southern Italy(Mercurella site)and a cooler,moister site in the northern Apennines without summer aridity(Acquerino).The relationship between tree-ring chronologies and monthly climatic variables was evaluated by a moving average and correlation analysis.Results showed that the minimum temperature in February and in March play a key role for Douglas-fi r at both sites,with a positive eff ect on growth.At the northern site,it is also highly sensitive to late summer temperatures(negative correlation)and spring–summer precipitation(positive correlation).Growth rates in southern latitudes were high even in Europe and in the Mediterranean environment,with low sensitivity to climatic fl uctuation.On the basis of our results,further common garden experiments should test adaptation and the interaction between genetics and environment of second-or third-generation seeds from old stands across Europe such as done by the old International Union of Forest Research Organizations(IUFRO)or the European Douglasfi r Improvement Research Cooperative(EUDIREC)experimentation programmes.

Mechanisms of bush encroachment and its inter-connection with rangeland degradation in semi-arid African ecosystems:a review

Many studies show that semi-arid rangelands throughout the world have been rapidly converted from a grassland state to a bush encroachment state during the past 50 years. Bush encroachment includes the spread of local woody species and/or incursion of woody species introduced from other ecosystems into semi-arid savannas and grassland ecosystems. Rangeland degradation due to bush encroachment causes several challenges, affecting the production of livestock and pastoral people livelihoods in most parts of Africa. Scientists have long been attempting to develop schematic and mathematical theories to explain the observed phenomenon of bush encroachment, and several theories were proposed and developed. The well-regarded theories include： （1） Waiter＇s two-layer model, （2） Moir＇s one-layer model, （3） state-and-transition theory, （4） equilibrium theory, （5） disequilibrium theory, and （6） non-equilibrium theory. Within those theories, the most frequently-indicated driving factors that explain bush encroachment include over-grazing, availability of soil nutrient and moisture, elevated CO2 levels, frequency and intensity of fire, spread of seeds of woody species by livestock and wild animals. It should be stressed that couplings and interactions among diverse driving factors are more often at work in determining the condition of bush encroachment. To summarize, the effort in managing semi-arid ecosystems needs critical knowledge to understand the cause-effect relationships of underlying factors through integrated approach. Therefore, future research on encroachment of woody plants should be multi-discipline oriented and multi-partnership involved.

Soil ecosystem changes by vegetation on old-field sites over five decades in the Brazilian Atlantic forest

Vegetation types alter soil ecosystems by changing soil fauna community activities and soil physi-cal-chemical properties.However,it is unclear how tree species(natural forest,native and exotic tree plantations)promote changes in the soil ecosystem,and if these changes alter functional groups of soil fauna and ecosystem services.To determine the effects of five decades of old-field veg-etation on soil ecosystems in the Brazilian Atlantic Forest,field sampling of three ecosystems(exotic tree species Pinus elliottii Engelm.plantation,endangered tree species Arau-caria angustifolia(Bertol.)Kuntze plantation,and a natural ecosystem)were carried out,as well using bait-lamina tests and bioassays with collembolans,earthworms and seeds of Lactuca sativa L.Field sampling evaluated the soil fauna community and soil physical-chemical properties.The bait-lamina test in situ was carried out for 14-days to deter-mine fauna feeding activity,and the bioassays evaluated the reproduction of Folsomia candida,the avoidance of Eisenia andrei,and germination of L.sativa in the soil from each ecosystem.The results are:(1)vegetation type altered the soil fauna community composition;(2)soil fauna feeding was reduced in the plantations compared to the natural eco-system;(3)a physical barrier was created by recalcitrant litter that compromised fauna community structure and seed bank germination in situ;and,(4)changes in soil physical-chemical properties promoted decomposers.

Dispersal patterns of exotic forest pests in South Korea

Invasive species have potentially devastating effects on ecological communi- ties and ecosystems. To understand the invasion process of exotic forest pests in South Korea, we reviewed four major species of exotic forest pests： the pine needle gall midge （Thecodiplosis japonensis）, pine wilt disease caused by the pine wood nematode （Bur- saphelenchus xylophilus）, the fall webworm （Hyphantria cunea） and the black pine bast scale （Matsucoccus thunbergianae）. We consider their biology, ecology, invasion history, dispersal patterns and related traits, and management as exotic species. Among these species, the dispersal process of fall webworm was linear, showing a constant range expan- sion as a function of time, whereas the other three species showed biphasic patterns, rapidly increasing dispersal speed after slow dispersal at the early invasion stage. Moreover, human activities accelerated their expansion, suggesting that prevention of the artificial movement of damaged trees would be useful to slow expansion of exotic species. We believe that this information would be useful to establish management strategies for invasion species.

Mountain invasions on the way:are there climatic constraints for the expansion of alien woody species along an elevation gradient in Argentina?

Aims Increasing evidence worldwide indicates that high mountain regions are not immune to invasion by alien plants.Here,we aimed to address whether three major woody invaders of low-mountain areas are constrained to lower altitudes due to climatic restrictions or just by low propagule pressure.We hypothesize that the increasing climatic harshness towards higher altitudes restricts seedling establishment and survival of these woody invaders and thus their potential for altitudinal expansion.Methods The study was carried out in the Sierras Grandes Mountains,Córdoba,central Argentina(32°50′S,64°90′W).We addressed the hypothesis with an experimental approach,dissociating the effect of the environmental gradient from that of propagule pressure,by discarding the influence of seed sources.We translocated seeds of Gleditsia triacanthos L.,Ligustrum lucidum W.T.Aiton.and Pyracantha angustifolia(Franch.)C.K.Schneid.along the altitudinal gradient(from 900 to 2700 m asl).Seven sites were selected along the altitudinal gradient,spaced every 200-400 m.Three plots(4×4 m)were selected within each altitudinal site and excluded from livestock;100 seeds of each species were sown within each plot(6300 seeds in total).Seedling emergence and survival was monitored during two growing seasons and soil temperature and moisture was recorded as well.The field experiment was complemented with lab assays.Important Findings Climate along this altitudinal gradient might be least restrictive at mid elevations,as a result of the intersection between opposite soil temperature and moisture gradients.Sown seeds germinated along the whole altitudinal gradient and seedlings successfully established and over-wintered well above their current altitudinal distribution(up to 2200 m for Ligustrum and 2400 m for Gleditsia and Pyracantha).Additional lab assays confirmed field patterns and gave some insights into contrasting regeneration strategies between these invaders that might help to overcome stochastic environmental constraints in the germination stage.Overall,seedlings of three major woody invaders of low-mountain woodlands can establish and survive at higher elevations than their current distribution.In contrast to natives,they seem to be broad climate tolerators,rather than specialized stress tolerators,capable of germinating and growing across a wide elevational range.While long-term experiments might be necessary to fully address the potentials for altitudinal expansion,out results on early lifecycle stage suggest that the invaders studied here would have mostly a dispersal barrier rather than a climate barrier to establish in the upper belt of the Sierras Grandes.

Does a giant tortoise taxon substitute enhance seed germination of exotic fleshy-fruited plants?

Aims The use of exotic species as taxon substitutes to restore lost ecological interactions is currently hotly debated.Aldabrachelys gigantea giant tortoises have recently been introduced to three islands in the Mascarene archipelago(Ile aux Aigrettes,Round Island and Rodrigues)to resurrect herbivory and seed dispersal functions once performed by extinct giant tortoises.However,potential unintended impacts by frugivore substitutes on native ecosystems,e.g.whether they will facilitate the germination of exotic plant species,are largely unknown.We investigated whether A.gigantea introduced to Rodrigues in 2006 could enhance the germination percentage of four widespread fleshy-fruited exotic species on the island.Using germination trials to forecast unintended impacts that could arise from the introduction of a frugivorous taxon substitute enables conservation managers to limit potential adverse negative interactions before they occur.Methods In germination trials that ran over 4 months,we investigated the effects of ingestion(gut passage and deposition in faeces)by subadult and adult A.gigantea on the germination percentage of four exotic fleshy-fruited plant species introduced to Rodrigues.We fed fruits of these plant species to sub-adult and adult A.gigantea to test how variation in age and size of the frugivore would affect seed germination.Feeding of distinctly coloured plastic pellets together with the fruits allowed us to test for individual tortoise effects on seed germination.Important Findings Ingestion by A.gigantea increased the percentage of seeds germinating of Mimusops coriacea and Lantana camara,but not percentage of germination of Veitchia merrillii or Wikstroemia indica.Seeds were more likely to germinate following ingestion by sub-adult rather than adult tortoises,which may be a consequence of the shorter gut passage time observed for sub-adults.Our results demonstrate that introduced frugivorous taxon substitutes could facilitate germination of exotic and invasive plants and highlight the need for conservation managers to weigh the risk of taxon substitutes potentially facilitating the germination and recruitment of exotic fleshy-fruited plants against the benefit of restoring lost seed dispersal functions of threatened indigenous plants.Our findings also highlight the importance of considering age and size variation in frugivores,in particular in long-lived taxa such as giant tortoises,when studying ingestion effects on the germination performance of plants.

Soil biotic and abiotic conditions negate invasive species performance in native habitat

Background:Most studies on plant invasion consider the enemy release hypothesis when analyzing native habitats.However,the lower performance of invasive species in the native habitats can be the result of unfavorable soil conditions in the native habitats.While soil biotic and abiotic factors have a potential to restrict the growth of invasive species in their native habitats,our understanding of belowground environment of invasive species in their native habitats is very limited.In this study,we analyzed soil characteristics associated with an exotic invasive plant,Old World Climbing Fern(Lygodium microphyllum),in its native habitat in Australia and the recipient habitat in South Florida.Rhizosphere soil samples from both habitats were analyzed for soil physical,chemical and biological characteristics.Results:Soil characteristics in the recipient habitats were significantly different compared to those in the native habitats.Soil samples from the native habitat had low soil pH,and high concentrations of elements such as aluminum and zinc which are phytotoxic in acidic soil environments.Additionally,mycorrhizal fungi spores were more diverse in the recipient habitat in Florida compared to the native habitat in Australia.Conclusion:Overall,our results indicate that growth of an invasive plant in its native habitats could be restricted by the toxic effects associated with strong soil acidity.Results from this study indicate that invasive plants not only escape from their natural herbivores but also from toxic soil environment in their native habitats.

Two new hyperspectral indices for comparing vegetation chlorophyll content

The red edge region of a hyperspectral vegetation reflectance curve provides important information regarding the biochemical and biophysical parameters of plants such as stress,senescence,and chlorophyll capacity.However,shifts of the red edge position(REP)to longer or shorter wavelengths have also been correlated with other factors such as water content,nitrogen,and salinity.These other factors can confuse the effect of chlorophyll on REP.The objective of this study is to define two new hyperspectral curve indices,the red valley width(RVW)and the chlorophyll absorption region(CAR)that are designed to provide less-sensitive characterizations of the chlorophyll content of vegetation in order to allow better comparisons among spatially or temporally distant populations of vegetation.The RVW and the CAR are both located in the visible near-infrared portion of the light spectrum and are derived from multiple hyperspectral curve features that have been found to be correlated with chlorophyll content,thus making them less sensitive to other biophysical and biochemical factors that can affect the REP independently.The robustness of the two new features is tested using the Leaf Optical Properties Experiment database,and the findings are used to compare two populations of saltcedar(Tamarix spp.)from a native habitat in China and an invasive habitat in the USA.Saltcedar is a highly invasive plant species in the USA but does not pose the same ecological and economic threats in its native habitat throughout Eurasia.The findings are interpreted in the context of the environmental characteristics of each region.

Invasibility and recoverability of a plant community following invasion depend on its successional stages

Exotic species invasion represent important causes of harming the structure,function,and ecological environment in ecosystems.Yet,knowledge remains limited on the invasibility(invasion advantage of exotic species)and recoverability(recovery ability of native species)of a plant community following invasion depend on its successional stages.We selected three grasses of Setaria viridis,Artemisia gmelinii,and Bothriochloa ischemum representing early(E),middle(M),and late(L)successional species,respectively.Meanwhile,the grasses of Panicum virgatum was selected to represent exotic species(invasion species).Three types of soil were collected to treat the three E,M,and L successional species,and one type of soil was collected to treat the exotic species.We compared the performance of the three native plant species and one exotic species grown in their“own”and“other”soils in a 2-year greenhouse experiment.Our study showed that exotic species performed better in soils of E and M successional species than in the soil of L successional species.After exotic species removed,E and M successional species exhibited poor growth in the soil of exotic species,while that of L successional species performed poor in field exotic species soils,but performed better in soils disturbed by exotic species.Our study demonstrated that the invasibility and recoverability of native plant communities changed with vegetation succession.

Recent introduction of an allodapine bee into Fiji： A new model system for understanding biological invasions by pollinators

Morphology-based studies have suggested a very depauperate bee fauna for islands in the South West Pacific, and recent genetic studies since have indicated an even smaller endemic fauna with many bee species in this region resulting from human-aided dispersal. These introduced species have the potential to both disrupt native pollinator suites as well as augment crop pollination, but for most species the timings of introduction are unknown. We examined the distribution and nesting biology of the long-tongued bee Braunsapis puangensis that was first recorded from Fiji in 2007. This bee has now become widespread in Fiji and both its local abundance and geographical range are likely to increase dramatically. The impacts of this invasion are potentially enormous for agriculture and native ecosystems, but they also provide opportunities for understanding how social insect species adapt to new environments. We outline the major issues associated with this recent invasion and argue that a long-term monitoring study is needed.