Impact of Plant Functional Group, Plant Species, and Sampling Time on the Composition of nirK-Type Denitrifier Communities in Soil

We studied the influence of eight nonleguminous grassland plant species belonging to two functional groups (grasses and forbs) on the composition of soil denitrifier communities in experimental microcosms over two consecutive years. Denitrifier community composition was analyzed by terminal restriction fragment length polymorphism (T-RFLP) of PCR-amplified nirK gene fragments coding for the copper-containing nitrite reductase. The impact of experimental factors (plant functional group, plant species, sampling time, and interactions between them) on the structure of soil denitrifier communities (i.e., T-RFLP patterns) was analyzed by canonical correspondence analysis. While the functional group of a plant did not affect nirK-type denitrifier communities, plant species identity did influence their composition. This effect changed with sampling time, indicating community changes due to seasonal conditions and a development of the plants in the microcosms. Differences in total soil nitrogen and carbon, soil pH, and root biomass were observed at the end of the experiment. However, statistical analysis revealed that the plants affected the nirK-type denitrifier community composition directly, e.g., through root exudates. Assignment of abundant T-RFs to cloned nirK sequences from the soil and subsequent phylogenetic analysis indicated a dominance of yet-unknown nirK genotypes and of genes related to nirK from denitrifiers of the order Rhizobiales. In conclusion, individual species of nonleguminous plants directly influenced the composition of denitrifier communities in soil, but environmental conditions had additional significant effects.     

Influences of Plant Species,Season and Location on Leaf Endophytic Bacterial Communities of Non-Cultivated Plants

Bacteria are known to be associated endophytically with plants. Research on endophytic bacteria has identified their importance in food safety, agricultural production and phytoremediation. However, the diversity of endophytic bacterial communities and the forces that shape their compositions in non-cultivated plants are largely uncharacterized. In this study, we explored the diversity, community structure, and dynamics of endophytic bacteria in different plant species in the Tallgrass Prairie Preserve of northern Oklahoma, USA. High throughput sequencing of amplified segments of bacterial rDNA from 81 samples collected at four sampling times from five plant species at four locations identified 335 distinct OTUs at 97% sequence similarity, representing 16 phyla. Proteobacteria was the dominant phylum in the communities, followed by the phyla Bacteriodetes and Actinobacteria. Bacteria from four classes of Proteobacteria were detected with Alphaproteobacteria as the dominant class. Analysis of molecular variance revealed that host plant species and collecting date had significant influences on the compositions of the leaf endophytic bacterial communities. The proportion of Alphaproteobacteria was much higher in the communities from Asclepias viridis than from other plant species and differed from month to month. The most dominant bacterial groups identified in LDA Effect Size analysis showed host-specific patterns, indicating mutual selection between host plants and endophytic bacteria and that leaf endophytic bacterial compositions were dynamic, varying with the host plant’s growing season in three distinct patterns. In summary, next generation sequencing has revealed variations in the taxonomic compositions of leaf endophytic bacterial communities dependent primarily on the nature of the plant host species.     

Arbuscular mycorrhizal fungal communities along a pedo-hydrological gradient in a Central Amazonian terra firme forest

Little attention has been paid to plant mutualistic interactions in the Amazon rainforest, and the general pattern of occurrence and diversity of arbuscular mycorrhizal fungi (AMF) in these ecosystems is largely unknown. This study investigated AMF communities through their spores in soil in a ‘terra firme forest’ in Central Amazonia. The contribution played by abiotic factors and plant host species identity in regulating the composition, abundance and diversity of such communities along a topographic gradient with different soils and hydrology was also evaluated. Forty-one spore morphotypes were observed with species belonging to the genera Glomus and Acaulospora, representing 44 % of the total taxa. Soil texture and moisture, together with host identity, were predominant factors responsible for shaping AMF communities along the pedo-hydrological gradient. However, the variability within AMF communities was largely associated with shifts in the relative abundance of spores rather than changes in species composition, confirming that common AMF species are widely distributed in plant communities and all plants recruited into the forest are likely to be exposed to the dominant sporulating AMF species.     

Endophytic fungal community in stems and leaves of plants from desert areas in China

Endophytic fungi are known to play important ecological roles in protecting plants from various abiotic and biotic stresses. Therefore, it is valuable to investigate the endophytic fungal community associated with plants distributed in harsh environments, such as deserts. Fungal communities in the stems and leaves of ten plant samples belonging to eight species were collected from a desert area in China and tested after plant surface sterilization. The fungal compositions were different among plants. Salsola collina, Suaeda salsa, and Coriospermum declinatum possessed the highest fungal richness. The colonization rates of these samples were high, exceeding 50% in eight of the samples. However, the fungal diversity of the samples was low when measured using Shannon??s index, Fisher??s ??, and Simpson??s index. Alternaria alternata, A. franseriae, Fusarium solani, and a second Fusarium species were most frequently isolated from all samples. The diversity of isolated species was low in desert areas, although the colonization rate was relatively high. It was concluded that fungal communities associated with plants in deserts had low diversity, but a small number of species colonized various plants with a high colonization rate. The Jaccard, Sorensen, and Bray?CCurtis similarity indices for the fungal communities were low between stems and leaves. This indicated that different fungal communities colonized these two tissues. Phoma pomorum and Phoma sp. showed tissue preferences.     

Quantitative ethnobotany of medicinal plants uses in the Jhelum valley,Azad Kashmir,Pakistan

Indigenous knowledge provides information on phytotherapeutic potential of medicinal plants for basic health care mangements in local communinites. The present study was aimed to document folklore knowledge of ethnic communities, who are practicing the herbal medicines in the Jhelum valley (District Hattian), Azad Kashmir, Pakistan. The information regarding folklore use of plants was collected from local communities through informed consent semi- structured interviews from 152 key informants. The ethnobotanical data were quantitatively analyzed using indices of use value (UV), relative frequency citation (RFC) and Informant census factor (ICF). A total of 113 medicinal plant species belong to 52 families were documented in the local communites of Jhelum Valley. The Asteraceae and Polygonaceae were the dominant plant families. The plant species hold potential folklore uses against hepatitis, stomach and respiratory problems, tooth ache, skin ailments and tumor treatment. The whole plants (32.52%), leaves ((21.14%)) were highly consumed plant parts and decoction (22.99%), powder form (18.39%) and infusion (13.79%) was the commonly used method for herbal formulation. The species with maximum use value was Beberis lyceum (0.80) and Valeriana jatamansi (0.60). The highest ICF value was obtained for disease catergories that is ear pain (1.00) followed by heaptic disorder (0.94) and urinary system disorders (0.89). The lowest ICF value was recored for nervous system disorders (0.44). The present study disclosed that traditional knowledge of medicinal plants is still widespread in ethnic people, but gradually decline in youngers. Documentation of newly documented plant species with their folklore uses shall uphold further phytochemical and pharmacological studies.     

An ethnobotanical study of the indigenous knowledge by the Rajbangshi community of Raiganj Block,Uttar Dinajpur district,West Bengal,India

BackgroundThe present study deals with documentation of medicinal importance of plants and traditional knowledge set harboring among the ethnic communities to utilize various plant parts for various health care practices. Twelve villages were surveyed primarily targeting the Rajbangshi communities of Raiganj Block, Uttar Dinajpur district, West Bengal, India.MethodsThe ethnomedicinal information was gathered through interviews using semi- structured questionnaires among the traditional healers (Kabiraj) of the Rajbangshi community. Identification and documentation of all the plants species have been completed following standard taxonomic procedure. The collected data were qualitatively and quantitatively analyzed through different ethnobotanical indices like, use report, informant consensus factor and relative importance.ResultsA total of 76 plant species belonging to 40 families and 72 genera were reported to have been utilized for the treatment of a total of 42 types of ailments. Herbs (43%) were the major source of medicine while roots (31%) were most frequently used plant parts. Preparation of juice (55%) from plant parts accounted as most preferred method. Achyranthes aspera L. has the highest calculated relative importance (100) value. The average informant consensus factor value for all ailments categories was 0.75, indicating a high level of consensus among the interviewed informants.ConclusionThe present study clearly demonstrates that huge diversity of medicinal plants reported in the study area may immensely help in the development of novel drugs of natural origin if the traditional knowledge set of the Rajbangshi community is adequately nurtured.     

Mammalian Herbivores Alter the Population Growth and Spatial Establishment of an Early-Establishing Grassland Species

Plant-herbivore interactions influence the establishment context of plant species, as herbivores alter the community context in which individual species establish, and the spatial relationship between individuals and their source population as plants invade. This relationship can be described using an establishment kernel, which takes into account movement through seed dispersal, and subsequent establishment of adults. Mammalian herbivores are hypothesized to influence plant population growth and establishment through a combination of consumption of seeds and seedlings, and movement of seeds. While the movement abilities of plants are well known, we have very few empirical mechanistic tests of how biotic factors like mammalian herbivores influence this spread potential. As herbivores of all sizes are abundant on the landscape, we asked the question, how do mammalian herbivores influence the population growth, spatial establishment, and the community establishment context of an early-recruiting native prairie legume, Chamaecrista fasciculata? We planted C. fasciculata in source populations within a four-acre tallgrass prairie restoration in plots with and without herbivores, and monitored its establishment with respect to distance from the source populations. We found that herbivores decreased population growth, and decreased the mean and range establishment distance. Additionally, C. fasciculata established more often without herbivores, and when surrounded by weedy, annual species. Our results provide insight into how the interactions between plants and herbivores can alter the spatial dynamics of developing plant communities, which is vital for colonization and range spread with fragmentation and climate change. Mammalian herbivores have the potential to both slow rates of establishment, but also determine the types of plant communities that surround invading species. Therefore, it is essential to consider the herbivore community when attempting to restore functioning plant communities.     

Colonization of Pneumatopteris afra (Christ) Holttum and its impact on some resident wetland communities in Nigeria

The widespread of invasive plants across the world has increased the risk of extinction of native plants. It is then necessary for understanding the ecological impacts of invasive plants on neighbouring plant communities where they are found. This study aimed to assess the impacts of the abundance of Pneumatopteris afra on plant diversity of some invaded wetlands in Lafia, Nigeria. Three wetlands with size 500 × 500 m² each were chosen. Forty 1.5 m × 1.5 m quadrats were laid at 10 m intervals across four 200 m transects at each wetland. The abundance of each plant species within the quadrats was counted and was used to estimate the diversity indices. The impact of the abundance of P. afra on the wetland communities was determined using Pearson correlation coefficients and linear regression models. A total of nine neighbouring plant species including P. afra were identified in all the sites. P. afra has the highest relative frequency and abundance in all the sites. Shannon and Simpson's diversity indices of all the sites are less than 2 showing that they are less diverse. The abundance of P. afra exhibited negative relationships with the diversity indices. Regression models also showed inverse relationships between P. afra and the diversity indices. The colonization of these wetlands by P. afra might be due to its ability to maximize disturbances and limit the growth and expansion of surrounding plants.     

Frugivory and the effects of ingestion by bats on the seed germination of three pioneering plants

The dispersion and seedling establishment of pioneering plants can be favoured by the presence of frugivorous bats because the bats usually improve seed germination after ingestion. Although seed germinability is known to vary greatly after ingestion by different bats, the relative contribution of each bat species to seed germination within plant communities is poorly understood. In this study, we first determined the fauna of frugivorous bats in a semideciduous seasonal forest remnant in southern Brazil and subsequently identified the plant species of the seeds passed through their guts. Second, the germination performance (i.e., germination percentage and speed) of the seeds of three pioneering plants (Piper aduncum, Piper hispidinervum and Solanum granuloso-leprosum) ingested by the most abundant bats was compared with that of the non-ingested seeds (seeds collected from fruits). Additionally, the effects on seed germination of different bat species were compared. During one year, five species of frugivorous bats were caught, and the seeds of eleven identifiable plant species (not counting those of undetermined species) were found in their faeces. We found that the germination performance of the seeds of Piper species was significantly enhanced after ingestion by bats, whereas S. granuloso-leprosum seeds had neutral or reduced germinability when seeds in faeces were compared with pulp-removed seeds. Our results revealed that the bat species that were captured exerted different effects upon seed germination; such a disparity is expected to result in different rates of early establishment of these pioneer plants in tropical forests, most likely affecting forest composition and structure, particularly during the initial stages of succession.     

Ethnobotanical study on pesticidal plants used in Southwest Nagaland,India for the development of eco-friendly pest control system

BackgroundManagement of crop pests has been a great challenge around the world. In this study, the plants that are traditionally used as pesticides in southwest Nagaland were identified and documented. Pesticidal plants are an effective alternative to harmful synthetic pesticides and they may help in the formulation of a diverse group of organic pesticides.MethodsInformation on pesticidal plants was obtained through field study and semi-structured interviews. 360 informants from 24 villages were interviewed. Data were analyzed through quantitative tools – use value (UV), informants consensus factor (ICF), fidelity level (FL), and family use value (FUV). Phytochemical analysis of selected plants was done.ResultsIn total, 113 species representing 104 genera and 46 families were documented as pesticidal plants. Asteraceae was the most preferred family as a pesticide with 17 species. Herbs were recorded for 43% of use which was the highest among the habitats. Out of 113 species, 105 species were used as insecticides. Leaf (57.3%; 98 species) was the highest use plant part as a source of pesticides. The highest UV was recorded for Nicotiana tabacum (0.46) with 165 use reports. The ICF value was recorded from 0.96 to 0.97. In regards to FL, several potential pesticidal plants including Azadirachta indica, N. tabacum, Capsicum frutescens, and Curcuma longa were identified with 100% FL each. Phytochemical analysis showed the presence of secondary metabolites like alkaloid, flavonoid, phenol, saponin, tannin, and terpenoid.ConclusionInhabited by a diverse tribal population, the southwest part of Nagaland is a hub of ethnobotanical knowledge. The present study was the first quantitative survey on the plants used as pesticides by the tribal communities of southwest Nagaland and would help modern pharmacology immensely in formulating organic pesticides.     

Non-trophic interactions in deserts: Facilitation,interference, and an endangered lizard species

Research on plant–animal interactions has been focused on direct consumer interactions (i.e. plants as resources), but non-trophic interactions including providing shelter or interference with movement can also affect the fine-scale distribution of animals. In particular, non-trophic interactions that are positive could support threatened animal populations. Positive interactions have been used in the restoration of plant communities, but have not yet been extended to the management of animal habitat. In this study, we tested the hypothesis that non-trophic interactions influence the occurrence of an endangered lizard species in an arid shrub-annual system. At a location known to have a population of blunt-nosed leopard lizards (Gambelia sila), we geotagged 700 shrubs, measured shrub morphometric traits, collected biomass samples, and surveyed for lizard presence using scat detection dogs over two years. Relative to 2014, in 2013 plant productivity was high and lizard scats were found more frequently in areas with low invasive grass cover (i.e. residual dry matter, RDM). In 2014, plant productivity was low because of an extreme drought year, and lizard scats were more frequently observed under shrub canopies, particularly those with relatively dense cover. These findings support the novel theory that positive non-trophic interactions are a critical form of plant–animal interactions in addition to consumption. Dominant shrubs can act as a foundation species by functioning as a basal node in structuring both plant and animal communities through a network of interactions. Managing dominant plants, in addition to habitat, is therefore important for conserving animal species in arid ecosystems.     

Neighbours matter: natural selection on plant size depends on the identity and diversity of the surrounding community

Plant diversity can affect ecological processes such as competition and herbivory, and these ecological processes can act as drivers of evolutionary change. However, surprisingly little is known about how ecological variation in plant diversity can alter selective regimes on members of the community. Here, we examine how plant diversity at two different scales (genotypic and species diversity) impacts natural selection on a focal plant species, the common evening primrose (Oenothera biennis). Because competition is frequently relaxed in both genotypically and species rich plant communities, we hypothesized that increasing diversity would weaken selection on competitive ability. Changes in plant diversity can also affect associated arthropod communities. Therefore, we hypothesized that diversity would alter selection on plant traits mediating these interactions, such as herbivory related traits. We grew 24 focal O. biennis genotypes within four different neighbourhoods: genotypic monocultures or polycultures of O. biennis, and species monocultures or polycultures of old-field species that commonly co-occur with O. biennis. We then measured genotypic selection on nine plant traits known to be ecologically important for competition and herbivory. Focal O. biennis plants were smaller, flowered for shorter periods of time, had lower fitness, and experienced greater attack from specialist predispersal seed predators when grown with conspecifics versus heterospecifics. While neither conspecific nor heterospecific diversity altered trait means, both types of diversity altered the strength of selection on focal O. biennis plants. Specifically, selection on plant biomass was stronger in conspecific monocultures versus polycultures, but weaker in heterospecific monocultures versus polycultures. We found no evidence of selection on plant traits that mediate insect interactions, despite differences in arthropod communities on plants surrounded by conspecifics versus heterospecifics. Our data demonstrate that plant genotypic and species diversity can act as agents of natural selection, potentially driving evolutionary changes in plant communities.     

An ethnobotanical survey of indigenous knowledge on medicinal plants used by the traditional healers of the Lwamondo area,Limpopo province,South Africa

The use of medicinal plants in the treatment and prevention of diseases is attracting the attention of scientists worldwide. Approximately 3000 plant species are currently used by an estimated 200,000 indigenous traditional healers in South Africa. The specific part of the plant used for medicinal applications varies from species to species, and from one traditional healer to another. This study was carried out to explore and record those plants and plant parts used for treating various human ailments by the traditional healers of the Lwamondo area in the Limpopo province, South Africa for medicinal purposes. Ethnobotanical data were collected from 30 traditional healers (24 females and 6 males) in the Lwamondo area of Venda, by means of a data capture questionnaire focusing on the local names of the medicinal plants, their medicinal uses, the plant parts used, and methods of preparation and of administering treatments to patients. The survey identified 16 medicinal plants from 7 families, with 14 genera, used to treat a range of ailments in the Lwamondo area. The Fabaceae family was the most commonly used plant family representing 43.8% of all the medicinal plants species recorded by this study, followed by the Varbenaceae family at 18.8%. The plant parts most frequently used were the roots (44.5%), followed by the leaves (25.9%), bark (14.8%), the whole plant (11%), and flowers (3.7%). Most of the traditional healers obtained their extracts by boiling the medicinal plants. The most often recurring ailment treated by healers was stomach problems, using 31.3% of all the medicinal plants reported in this study for preparing such treatments. The following medicinal plants were covered by this study: Annona senegalensis, Schkuhria pinnata, Diospyros mespiliformis, Piliostigma thonningii, Senna obtusifolia, Bauhinia galpinii. The rural communities of the Lwamondo area possess a wealth of information on medicinal plants and their applications. This ethnobotanical survey can help scientists identify for further research those plants whose medicinal properties may be useful in the development of new drugs.     

Effects of urbanisation on the parasitoid community of a leafminer

Urbanisation may have detrimental effects on communities of parasitoids, affecting their species richness, abundance, and species dominance. Here we investigated the influence of the degree of urbanisation on parasitoid communities of Liriomyza commelinae (Frost) (Diptera: Agromyzidae), a leafminer of Commelina erecta L. (Commelinaceae), in the city of Córdoba, Argentina. To study changes in species richness, the specific composition of parasitic complexes and their degree of impact on the leafminer, 18 sampling sites from the centre to the outskirts of the city were selected and different variables indicative of urbanisation were quantified in each site. During January and February of 2005 and 2006, all mined leaves found in each plant patch were collected and the following variables were estimated: proportion of mined patches, abundance of the leafminer, total parasitoid species richness, total parasitism rates and parasitism due to the most abundant parasitoid species. The percentage of mined patches and leafminer abundance increased with urbanisation degree. Estimates of parasitoid species richness were not influenced by urbanisation degree but increased with species richness of mined plants. Changes in the specific composition of species along the urbanisation gradient were observed. Although parasitism by one of the species studied was higher in more urbanised sites of the city, the total parasitism rate of L. commelinae was not affected by urbanisation degree, species richness of mined plants or leafminer abundance. It appears that urbanisation benefits the herbivore species here studied but not through altering parasitoid activity. Changes in parasitoid community composition reflex dissimilar tolerance to environmental conditions displayed by different parasitoid species.     

An invasive plant provides refuge to native plant species in an intensely grazed ecosystem

Invasion by exotic plant species and herbivory can individually alter native plant species diversity, but their interactive effects in structuring native plant communities remain little studied. Many exotic plant species escape from their co-evolved specialized herbivores in their native range (in accordance with the enemy release hypothesis). When these invasive plants are relatively unpalatable, they may act as nurse plants by reducing herbivore damage on co-occurring native plants, thereby structuring native plant communities. However, the potential for unpalatable invasive plants to structure native plant communities has been little investigated. Here, we tested whether presence of an unpalatable exotic invader Opuntia ficus-indica was associated with the structure of native plant communities in an ecosystem with a long history of grazing by ungulate herbivores. Along 17 transects (each 1000 m long), we conducted a native vegetation survey in paired invaded and uninvaded plots. Plots that harboured O. ficus-indica had higher native plant species richness and Shannon–Wiener diversity H′ than uninvaded plots. However, mean species evenness J was similar between invaded and uninvaded plots. There was no significant correlation between native plant diversity and percentage plot cover by O. ficus-indica. Presence of O. ficus-indica was associated with a compositional change in native community assemblages between paired invaded and uninvaded plots. Although these results are only correlative, they suggest that unpalatable exotic plants may play an important ecological role as refugia for maintenance of native plant diversity in intensely grazed ecosystems.     

Effect of bacterial inoculation,plant genotype and developmental stage on root-associated and endophytic bacterial communities in potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis>)

Beneficial bacteria interact with plants by colonizing the rhizosphere and roots followed by further spread through the inner tissues, resulting in endophytic colonization. The major factors contributing to these interactions are not always well understood for most bacterial and plant species. It is believed that specific bacterial functions are required for plant colonization, but also from the plant side specific features are needed, such as plant genotype (cultivar) and developmental stage. Via multivariate analysis we present a quantification of the roles of these components on the composition of root-associated and endophytic bacterial communities in potato plants, by weighing the effects of bacterial inoculation, plant genotype and developmental stage. Spontaneous rifampicin resistant mutants of two bacterial endophytes, Paenibacillus sp. strain E119 and Methylobacterium mesophilicum strain SR1.6/6, were introduced into potato plants of three different cultivars (Eersteling, Robijn and Karnico). Densities of both strains in, or attached to potato plants were measured by selective plating, while the effects of bacterial inoculation, plant genotype and developmental stage on the composition of bacterial, Alphaproteobacterial and Paenibacillus species were determined by PCR-denaturing gradient gel-electrophoresis (DGGE). Multivariate analyses revealed that the composition of bacterial communities was mainly driven by cultivar type and plant developmental stage, while Alphaproteobacterial and Paenibacillus communities were mainly influenced by bacterial inoculation. These results are important for better understanding the effects of bacterial inoculations to plants and their possible effects on the indigenous bacterial communities in relation with other plant factors such as genotype and growth stage.     

Minimal Effects of an Invasive Flowering Shrub on the Pollinator Community of Native Forbs

Biological invasions can strongly influence species interactions such as pollination. Most of the documented effects of exotic plant species on plant-pollinator interactions have been observational studies using single pairs of native and exotic plants, and have focused on dominant exotic plant species. We know little about how exotic plants alter interactions in entire communities of plants and pollinators, especially at low to medium invader densities. In this study, we began to address these gaps by experimentally removing the flowers of a showy invasive shrub, Rosa multiflora, and evaluating its effects on the frequency, richness, and composition of bee visitors to co-flowering native plants. We found that while R. multiflora increased plot-level richness of bee visitors to co-flowering native plant species at some sites, its presence had no significant effects on bee visitation rate, visitor richness, bee community composition, or abundance overall. In addition, we found that compared to co-flowering natives, R. multiflora was a generalist plant that primarily received visits from generalist bee species shared with native plant species. Our results suggest that exotic plants such as R. multiflora may facilitate native plant pollination in a community context by attracting a more diverse assemblage of pollinators, but have limited and idiosyncratic effects on the resident plant-pollinator network in general.     

Resistance of plant communities to invasion by tall fescue: An experimental study combining species diversity,functional traits and nutrient levels

The grass Festuca arundinacea is often planted for slope stabilisation in South Korea, and is spreading widely beyond the introduction sites. This study used a functional group approach to examine the resistance of plant combinations to invasion by F. arundinacea based on the limiting similarity and diversity-resistance hypotheses, and to elucidate the process of colonisation. The study simulated the environment of construction sites and surrounding areas that might be encountered by expanding populations of F. arundinacea. The role of nutrient condition in the ranking of functional group competitive ability was also examined. Twelve native plant species were categorised into three functional groups using combinations of functional traits. Pairwise (one-to-one competition), multiple (four different neighbouring species) and monoculture experimental settings were designed using two nutrient levels. The Relative Competition Index was used to interpret the competitive effect of neighbouring species on F. arundinacea. Species of the same functional group as F. arundinacea were unable to resist invasion, but annual plants with niche preemption ability could outcompete it. Competitive relationships between native plants and F. arundinacea were explained partially by functional group identity but were inconsistent with the limiting similarity hypothesis and the diversity-interaction. Unforeseen interactions within the artificial communities also produced unexpected effects. In designing artificial plant communities, it is necessary to consider functional traits that reflect the species characteristic of particular periods and indirect effects that modify the interaction between other species.     

Effect of plant species on communities of arbuscular mycorrhizal fungi in the Mongolian steppe

Communities of arbuscular mycorrhizal (AM) fungi were investigated in Stipa krylovii, Leymus chinensis (Poaceae), Allium bidentatum (Liliaceae), and Astragalus brevifolius (Fabaceae) in the Mongolian steppe to examine the effect of plant species on the communities in this study. The AM fungal communities were examined by molecular analysis based on the partial sequences of a small subunit of the ribosomal RNA gene. The sequences obtained were divided into 23 phylotypes by the sequence similarity >98%. Many of the AM fungal phylotypes included AM fungi previously detected in high-altitude regions in the Tibet and Loes plateaus, which suggested that these AM fungi may have wide distribution with stressful conditions of aridity and coldness. Among the 23 phylotypes, 12 phylotypes were found in all four plants, and 87.4% of the all obtained sequences were affiliated into these 12 types. For the distribution of the AM fungal phylotypes, overlapping of the phylotypes among the four plant species were significantly higher than that simulated by random chance. These results suggested that AM fungal communities were less diversified among the examined plant species.     

Native and Non-Native Plants Provide Similar Refuge to Invertebrate Prey,but Less than Artificial Plants

Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant’s native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (Daphnia pulex, Gammarus pulex and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton perfoliatus) and non-native plants (Vallisneria spiralis, Myriophyllum heterophyllum, Cabomba caroliniana). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: Cyprinus carpio carpio and dragonfly larvae: Anax imperator) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (Ceratophyllum demersum), may interact with structural complexity to play a key role in refuge provisioning to specific prey (Gammarus pulex). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants.