Exotic Invasive Species Research Articles

Molecular survey of porcine respiratory disease complex pathogens in Brazilian wild boars

Wild boar (Sus scrofa) is an exotic invasive species in Brazil and may be a reservoir for several pathogens, including those related to the porcine respiratory disease complex (PRDC), a critical infectious disease in pig production. The objective of this study was to investigate viral and bacterial pathogens related to PRDC in free-living wild boars from Brazil. Eighty animals were examined in search of genomes of porcine circovirus 2 (PCV2), Torque teno Sus virus 1a (TTSuV1a) and 1b (TTSuV1b), Influenza A virus (IAV), Actinobacillus pleuropneumoniae, Glaesserella parasuis, Pasteurella multocida, and Mycoplasma hyopneumoniae. The results demonstrated that 57.5% (46/80) of the animals had at least one detected pathogen, and 11.3% of them (9/80) were co-infected. TTSuV1a was the most prevalent genome, for which risk factors were associated with increased contact between wild boars and other animals. The other pathogens were detected at much lower frequencies or not detected (M. hyopneumoniae and IAV). An additional IAV serology search identified H1N1pdm09 antibodies in 35.5% (16/45) of the wild boars, bringing concern related to public health. In conclusion, wild boars are infected with pathogens that cause swine diseases, so their eventual contact with domestic pigs might risk animal production in Brazil.

Nitrogen addition, but not pulse frequency, shifts competitive interactions in favor of exotic invasive plant species

Nitrogen addition, but not pulse frequency, shifts competitive interactions in favor of exotic invasive plant species

Reinventory of the vascular plants of Mormon Island Crane Meadows after forty years of restoration, invasion, and climate change

The majority of tallgrass prairie has been lost from North America's Great Plains, but remaining tracts often support significant biodiversity. Despite permanent protections for some remnants, they continue to face anthropogenic threats including habitat fragmentation, invasive species, and climate change. Conservationists have sought to buffer remnants from threats using prairie restoration but limited research has assessed such practices at the landscape-level. We reexamine the flora of Mormon Island, the largest tract of lowland tallgrass prairie remaining in the Central Platte River Valley (CPRV) of Nebraska, USA, nearly 40-years after it was initially inventoried and following widespread restoration. We also conducted preliminary inventories of nearby Shoemaker Island and adjacent off-island habitats using an ecotope-based stratified random sampling approach. We examined change at Mormon Island between 1980-1981 and 2015–2020 and compared it to adjacent conservation lands using a number of vegetation indices. We documented 389 vascular plant species on Mormon Island, 405 on Shoemaker Island, and 337 on off-island habitats from 2015-2020, which represented an increase in native and exotic species richness on Mormon Island compared to 1980–1981 results. Floristic quality index (FQI) values increased at Mormon Island between 1980-1981 and 2015–2020. Paradoxically, the distribution of exotic-invasive species also expanded. Mormon Island from 2015-2020 was more similar to Shoemaker Island and off-island habitats from 2015-2020 than Mormon Island from 1980-1981. Widespread restoration introduced a number of high conservation value species native to Nebraska but novel to the CPRV, which improved FQIs despite increased exotic species invasion. These concurrent trends appear to have driven biological homogenization across the study area. Restoration did not fully buffer Mormon Island from exotic species invasion but it may have partially mitigated the impact considering the persistence of most native species across a 40-year period. We recommend using “local ecotype” seed for restorations to preserve distinctive local communities.

Impact of invasive insects on native insect communities

Several biophysical factors are leading to the loss of biodiversity, among them the dominance of exotic invasive species on native communities is important. Their dominance can lead to changes in the structure of insect communities, by competing and displacing native species to other crops or habitats. These changes can impact the herbivore's natural enemies in invaded areas by diverging them from suitable herbivores and altering their biological control process. The development of edible insects and derived products at an industrial scale can also have an impact on the local fauna by the risks of spillover and accidental release in nature. Several area-wide integrated pest management programs are also using the sterile insect technique to control insect pests and disease' vectors. This technique is becoming largely used; however, its application as 'non-intrusive to the environment' is controversial particularly when eradication is concerning species that are at the basis of food webs.

A Green New Balance: Interactions among riparian vegetation plant traits and morphodynamics in alluvial rivers

AbstractThe strength of interactions between plants and river processes is mediated by plant traits and fluvial conditions, including above‐ground biomass, stem density and flexibility, channel and bed‐material properties, and flow and sediment regimes. In many rivers, concurrent changes in (1) the composition of riparian vegetation communities as a result of exotic species invasion and (2) shifts in hydrology have altered physical and ecological conditions in a manner that has been mediated by feedbacks between vegetation and morphodynamic processes. We review how Tamarix, which has invaded many southwestern US waterways, and Populus species, woody pioneer trees that are native to the region, differentially affect hydraulics, sediment transport, and river morphology. We draw on flume, field, and modelling approaches spanning the individual seedling to river‐corridor scales. In a flume study, we found that differences in the crown morphology, stem density, and flexibility of Tamarix compared to Populus influenced near‐bed flow velocities in a manner that favoured aggradation associated with Tamarix. Similarly, at the patch and corridor scales, observations confirmed increased aggradation with increased vegetation density. Furthermore, long‐term channel adjustments were different for Tamarix‐ versus Populus‐dominated reaches, with faster and greater geomorphic adjustments for Tamarix. Collectively, our studies show how plant‐trait differences between Tamarix and Populus, from individual seedlings to larger spatial and temporal scales, influence the co‐adjustment of rivers and riparian plant communities. These findings provide a basis for predicting changes in alluvial riverine systems which we conceptualize as a Green New Balance model that considers how channels may adjust to changes in plant traits and community structure, in addition to alterations in flow and sediment supply. We offer suggestions regarding how the Green New Balance can be used in management and invasive species management.

Gillnet Selectivity for Three Freshwater Alien Invasive Fish Species in a Long-Term Monitoring Scenario

Gillnet selectivity is poorly understood for most freshwater fish species, particularly for invasive alien species. However, their use to determine mesh selectivity could be essential for establishing management measures, such as the selective removal of exotic invasive species. This study aims to the assess size selectivity of exotic invasive species in a restored lentic freshwater ecosystem. Therefore, we analysed gillnet size selectivity based on experimental fishing trials performed by using multimesh gillnets. Twice a year, for 8 years, multimesh nylon gillnets were set up in the Estany d’Ivars i Vila-sana, a restored shallow lake in Catalonia (NE Iberian Peninsula). We caught 4105 individuals belonging to three widely distributed freshwater fish species—3583 pikeperches (Sander lucioperca (Linnaeus, 1758)), 115 common roaches (Rutilus rutilus (Linnaeus, 1758)) and 407 common carps (Cyprinus carpio, Linnaeus, 1758). The SELECT method was applied to fit six different gillnet selectivity uni- and bimodal models. As a result, bi-lognormal provides the best fit for the three species. This is in line with previous studies that found size–frequency data skewed to the right or to multimodal models when high numbers of fish are captured. These results provide the essential information required for fish community management with the presence of these invasive alien species.

Predicting the Risk of Exotic Plant Invasions in the Orinoco Region: Importance of Distribution Models, Climatic Niche and Functional Richness

The process of biological invasions resulting from the introduction of exotic species is one of the most critical components of global environmental change. Although many hypotheses try to explain the processes underlying biological invasions, changes in land use are essential drivers mediating the colonization of exotic species at the landscape level. We used potential species distribution models developed in Maxent and a database of nine functional traits associated with invasion success for 18 exotic species with a high risk of establishment and difficulty of control in the Orinoco region from Colombia. We found that 67% of the species differed from the centroid in the climatic niche when comparing native and invaded localities. Overall, the native distribution localities showed a more restricted dispersal in their climatic niche, and for most species, native distribution was found within the broad environmental gradients of the invaded localities. Additionally, we found high climatic suitability for all exotic species across all the biomes and ecosystems; however, transformed ecosystems showed exotic plant species’ higher potential functional richness. Our research allowed us to identify key geographical areas that are highly susceptible to invasions and prioritize species that need control in particular ecosystems and biomes. This work provides early warnings on the potential risks of invasion of exotic species, and it will improve the monitoring and management efforts in the Orinoco region of Colombia.

EDNA Analysis of Goat‐Grazed Rhamnus cathartica Soil Microbial Communities

Biological invasions of exotic species pose a significant threat to local biodiversity and ecosystem services. Redistribution of plant species in particular disrupts key structure‐function relationships in the soil by altering the composition of microbial taxa. This study combines environmental DNA analysis with a goat‐grazing intervention to investigate the taxonomic structure of soil microbiomes interacting with the invasive plant, Rhamnus cathartica (common Buckthorn). 16S (515F/806R) metabarcodes were amplified from soil DNA harvested before and after a goat‐grazing regimen on buckthorn‐invaded and control plots. Samples were sequenced on an Illumina iSeq, then analyzed using the DNA Subway Purple Line (QIIME 2.0) to process sequencing reads and calculate diversity indices. PCoA visualizations of Jaccard Beta diversity patterns revealed differences in community composition between buckthorn and control soils, but no effects from goat grazing. Five dominant taxa were identified in no‐buckthorn control soils, accounting for 35 +/‐ 9.6 SD% of the average relative abundance of total sequences. Genus DA101 notably demonstrated the largest decrease in average relative abundance in the buckthorn and goat‐grazed soils (% decrease = 6.4 +/‐ 2 SD), whereas the evenness of other taxa increased. Overall, buckthorn soil showed significant increases in Pielou’s taxonomical evenness (Kruskal‐Wallis H(2, N=29) = 10.9; p=0.004), but goat grazing had no impact on this score (p>0.01). Faith’s phylogenetic diversity scores showed no significant differences between buckthorn, goat‐grazed, and control soils (Kruskal‐Wallis H(2, N=31) = 2.2; p=0.32). Taken together, these preliminary results illustrate that buckthorn increases taxonomical evenness but has no effect on overall phylogenetic diversity of soil communities. Moreover, buckthorn goat‐grazing had little impact on soil community structure. Future studies will investigate the role of DA101 on buckthorn suppression as a possible mitigation strategy for this invasive species.

What common‐garden experiments tell us about climate responses in plants

Abstract Common garden experiments are indoor or outdoor plantings of species or populations collected from multiple distinct geographic locations, grown together under shared conditions. These experiments examine a range of questions for theory and application using a variety of methods for analysis. The eight papers of this special feature comprise a cross section of contemporary approaches, summarized and synthesized here by what they tell us about the relationships between climate‐related trait spectra and fitness optima. Four of the eight papers are based on field experiments in prairie, desert, Mediterranean and boreal biomes. Representative of many common garden experiments, these experiments reveal consistent evidence of traits varying with population climate provenance, but evidence of a tradeoff between growth and tolerance traits or of consistent fitness optimization at home is scant, in contrast to trait theory. Two synthesis papers highlight dominant patterns of trait divergence, including for an exotic invasive species. One theoretical paper warned that unknown kinship relationships between populations can result in the misidentification of adaptive trait divergence. A third synthesis paper formulated novel and ambitious goals for common‐garden studies through including measurement of response variables at multiple levels of biological organization. The featured papers discuss multiple avenues for improving common garden studies. Genomic analysis, together with the quantification of kinship relationships, will continue to reveal the influence of environmental drivers on gene selection. Measuring a more complete set of fitness traits, especially for traits related to regeneration, will permit the development of projection models to explicitly link trait spectra, climate patterns and fitness consequences. More standardized data reporting will additionally improve abilities to synthesize findings across experiments. Testing population performance in competition with other species will produce more robust fitness comparisons between genotypes, especially for slower‐growing genotypes in higher‐resource environments. Adding gardens in and beyond climatic edge locations will furthermore strengthen the understanding of population failure and species exclusion. Finally, there is unrealized potential in adding ecosystem‐level observations to common‐garden studies that will enhance integrative analysis across scales of biological organization and scientific domains. Synthesis. With novel, creative designs, data integration and synthesis, common garden experiments will continue to advance the understanding of trait ensembles interacting with climate across scales of biological organization, provide pivotal data for global change models and guide ecological applications such as restoration of habitats for rare and climate sensitive species.

Interactive effects of allelopathy and arbuscular mycorrhizal fungi on the competition between the invasive species Bidens alba and its native congener Bidens biternata

AbstractAllelopathy is an invasion driver, and arbuscular mycorrhizal fungi (AMF) also play an important role in plant invasion. However, little is known about their interactive effects on plant invasion mechanisms. In this study, we have investigated the interactive effects of allelopathy and AMF on competition between the exotic invasive species, Bidens alba, and its native congener, Bidens biternata. A two‐factor (allelopathy, AMF) common garden experiment was conducted using sterilised soil with or without AMF inoculation and with or without activated carbon (AC) addition. The results showed that both AC and AMF had significant effects on the relative yield (RY) of invasive species and competitive aggressivity (AG) between invasive and native species. Both AC and AMF exerted interactive effects on the AG. Activated carbon significantly reduced AG (0.86 vs 0.15%) without AMF, while it had no significant effects on AG with AMF. Moreover, AC significantly reduced the mycorrhizal dependency of the native species (108.06% vs 23.62%) but did not affect the invasive species. The AMF increased the variety of organic compounds in the aqueous extracts of the rhizosphere soil of invasive species, regardless of the competition. Overall, allelopathy significantly increased the mycorrhizal dependency of the native species, while it promoted the competitive ability of the invader regardless of AMF inoculation. Conversely, AMF reduced the facilitation of allelopathy in the AG of the invasive species. These results suggest that AMF play a critical role in improving the resistance of the native species to the invader by mediating allelopathy.

Invasive Insects Outbreaks in India during the 21st Century-threat and Management

The word “Exotic” is developed from the Greek and Latin word meaning “not of a native species, or “alien species”. Alien arthropods threaten human health, threaten, food security, endanger valued species and disrupt ecosystem functions. The accelerating pace of commercialization and globalization creates opportunities for the movement of species to new areas of the world. Economic liberalisation has accelerated the movement of goods across borders and geographic obstacles without minimal quarantine, increasing the risk of exotic pest introduction into agroecosystems. Invasive Alien Species (IAS) are often regarded as one of the most serious dangers to the country's ecological and economic health. These species have a huge impact on biodiversity and natural agriculture systems, which are both extremely valuable. Pest invasions have lately been identified as a significant source of biodiversity loss. Preventing exotic species invasions is one of the most effective ways to limit the chance of invasion, but this requires recognising potential invasive species ahead of time.

Western boundary currents drive sun-coral (Tubastraea spp.) coastal invasion from oil platforms

Most marine species have a planktonic larval phase that benefit from the surface oceanic flow to enhance their dispersion potential. For invasive species, the interaction of environmentally resistant larvae with different flow regimes and artificial substrates can lead to complex larval dispersion patterns and boost geographic expansion. In the Southwest Atlantic, the invasive corals Tubastraea spp. (sun-coral) have been recorded biofouling on oil platforms since the late 1980s. These platforms are considered important vectors for the established populations throughout the Brazilian coast. However, we still do not know how the position of these structures relative to regional flow contribute to the natural dispersion potential of these invaders on a regional scale. Herein, we used an eddy-resolving ocean model (ROMS) and an Individual Based Model (IBM-Ichthyop) to simulate the natural dispersion patterns of sun-coral larvae from all oil platforms on Brazilian oil-producing basins, for the austral summer and winter along 6 years (2010–2015) in 90-day simulations. We found that mortality rates by advection were significantly higher during the winter (p = 0.001) and when sources of larvae were compared throughout this season (p = 1.9 × 10–17). The influence of two western boundary currents and persistent eddy activity contribute to the dispersal of larvae to distances up to 7000 km. The effectiveness of each oil-producing basin as vectors for the entire Brazilian coastline, measured as the percentage of larval supply, highlights the importance of the northern Ceará (59.89%) and Potiguar (87.47%) basins and the more central Camamu (44.11%) and Sergipe-Alagoas (39.20%) basins. The poleward shift of the Southern branch of the South Equatorial Current during the winter causes larvae released from the Sergipe-Alagoas and Camamu basins to enter the North Brazil Current, expanding their dispersion towards the north. The Brazil Current disperses larvae southwards, but strong mesoscale activity prevents their dispersion to the coast, especially for those released from the oil platforms on Campos and Santos basins. Within this complex hydrodynamic setting, a few source areas, like those in the Sergipe-Alagoas and Camamu basins, can potentially contribute to the spread of larvae along nearly all the Brazilian coast. Therefore, oil platforms act as possible chronic sources of sun-coral propagules to the coast, emphasizing the urgency for a more detailed set of actions to control and monitor these invasive exotic species.

Effects of competition and habitat heterogeneity on native‐exotic plant richness relationships across spatial scales

AbstractAimThe biotic resistance hypothesis posits that greater native species richness limits invasions of exotic species. However, negative native‐exotic richness relationships (NERRs) may reverse with increasing spatial scale, seemingly refuting the hypothesis. Here, we explore the effects of species competitive interactions, environmental factors, habitat heterogeneity and vertical vegetation tiers on the NERRs across spatial scales in native forests.LocationNew Zealand.MethodsWe combined vegetation, land cover and climate data to predict exotic richness from native richness at different vertical tiers (ground to canopy), land cover, plant competition (tree basal area, native ground cover), mean annual temperature and total rainfall. We considered four spatial scales, from single 20 × 20 m plots on an 8‐km grid to groups of plots across grids up to 128 km. Habitat heterogeneity was measured using the variance of climatic conditions among plots within a group.ResultsA negative native tree‐exotic richness relationship (NTERR) was observed at plot level but reversed with increasing spatial scale. Species competitive interactions showed a negative relationship with exotic richness at small/intermediate scales (≤32 km). Rainfall and temperature heterogeneity contributed to the positive NTERR at the largest scale. Adjacent exotic grassland cover had a positive relationship with exotic richness across all scales but did not prevent the NTERR from reversing.Main conclusionsOur analysis shows the importance of considering vegetation structure and adjacent land covers, along with spatial heterogeneity and climatic factors, when testing the biotic resistance hypothesis in forest ecosystems. There is a clear indication that biotic resistance is primarily driven by native trees in the overstorey, probably by limiting resources available to ground tier plants. The results support the notion that the NERR is driven by competitive interspecific interactions at small spatial scales and by habitat heterogeneity at larger scales.

Comparison of isopod assemblages (Crustacea: Isopoda: Oniscidea) among four different habitats—Evergreen forest, exotic bamboo plantation, grass and urban habitat

Exotic plantations and urbanization are serious threats to biodiversity. This study compared community structures of terrestrial isopods among urban habitat, grass, exotic bamboo forest and broad-leaved forest. A total of 9553 terrestrial isopod specimens from 11 native and 5 exotic species were collected from 102 sites. Nonmetric multidimensional scaling (NMDS) and non-hierarchical clustering showed that the community structure in exotic bamboo forest was similar to that in broad-leaved forest, and the communities were characterized by four native and one exotic species. However, the abundance in exotic bamboo forest was the lowest among the four habitats. The urban habitat was dominated by exotic species, and the species richness was the highest out of the four habitats. The results showed that exotic bamboo forest maintained an isopod community similar to that in broad-leaved forest, and that urbanization encouraged invasion of exotic species and increased species richness at a local scale.

Distribution of invasive exotic species Artocarpus heterophyllus Lam. in a forest fragment in the Amazon

Artocarpus heterophyllus is an invasive exotic species known for its negative impacts on Brazilian ecosystems. The aim of this study was to evaluate the distribution and population structure of A. heterophyllus in the plant community of a forest fragment in the Amazon. Individuals of this species were subject to active search at Sumaúma State Park, in Manaus, and two plots were delimited, where these individuals were counted. In each plot, the jackfruit tree individual with the largest Diameter at Breast Height (DBH) was centralized, and from it, native species were inventoried. The parameters of relative density, relative dominance and the importance value index were estimated. Jackfruit tree individuals in the plots had grouped distribution and their number in plots 1 and 2 was 308 and 872 individuals, respectively. In quadrant 1, 254 jackfruit trees and 118 native individuals were recorded, and in quadrant 2, 629 jackfruit and 130 native individuals. The jackfruit tree reached indices higher than the sum of the phytosociological indices of all native species. Jackfruit tree distribution was considered similar to that occurring in other already invaded areas of Brazil, which may indicate that the same impacts may occur in Amazonian ecosystems.

Biocrusts Influence Vascular Plant Community Development, Promoting Native Plant Dominance

The soil and its biota can shape the development of colonizing vascular plant communities. Because they occupy soil surfaces where most seeds disperse to, biological soil crusts (biocrusts) are uniquely positioned to influence vascular plant communities established by direct seeding, e.g., for restoration. We created mesocosms of soil overtopped by intact biocrust transplants from the field, varying in key community attributes: total cover, species richness, and proportional cover of mosses relative to lichens. We seeded the same diverse mixture of vascular plants into all mesocosms, including desired native species and problematic exotic invasive species. We tracked plant community development for two full growing seasons, both under ambient outdoor conditions and with supplemental irrigation to remove the influence of water limitation. Under ambient conditions, we found that total biocrust cover suppressed exotic plant emergence and biocrust richness slightly promoted native emergence (r = −0.23 to −0.39) but had weaker and less consistent effects on cover of either native or exotic plants (r ≤ |0.25|). Early emergence events were generally strong drivers of vascular plant recruitment (r = 0.17–0.78) and continued to influence community composition after 2 years, suggesting a priority effect. Biocrust cover also promoted final plant biomass under ambient conditions (r = 0.17–0.33) but did not influence the total cumulative number of native species (r ≤ |0.07|) nor the fecundity of exotics (r ≤ |0.08|). Biocrusts’ influence on total vascular plant biomass was minor. When water was added, biocrust effects sometimes switched from positive or negative to neutral, or vice-versa, indicating that our detection probability of biocrust effects on plants changes with moisture availability. Our results demonstrate that the condition of pre-existing biocrust communities can influence—but not strongly dictate—the outcome of multi-species restoration seedings, mostly positively or neutrally under normal conditions, but switching to potentially negatively under irrigated conditions. Our study also suggests that locations with more intact and richer biocrust communities might be slightly more conducive to successful seeding outcomes, while also providing additional contributions to ecosystem functions. As such, biocrusts, alongside vascular plants, have a role in restoring damaged or degraded ecosystems.

Biodiversity and Ecosystem Functions Across an Afro-Tropical Forest Biodiversity Hotspot

Ecosystem functions are important for the resilience of ecosystems and for human livelihood quality. Intact habitats and heterogeneous environments are known to provide a large variety of ecosystem functions. Natural and near natural ecosystems surrounding agroecosystems may positively support crop growing conditions and thus facilitate crop yields. In contrast, monocultures of crops and trees as well as degraded landscapes are known to provide less ecosystem functions. The Taita Hills in southern Kenya are part of the Eastern Afromontane biodiversity hotspot, and represent a habitat mosaic consisting of largely intact cloud forests, agroecosystems and plantations of exotic trees. In this region, subsistence farmers rely on ecosystem functions provided by natural ecosystems. In this study, we analyze three proxies of biodiversity and ecosystem functions, namely pollination activity, predation rates, and arthropod diversity in tree canopies. We set study plots along forest-agroecosystem-gradients, covering cloud forest, forest edge and agricultural fields, as well as plantations of exotic trees. We assessed environmental conditions, to evaluate the extent to which local environmental factors influence ecosystem functions. Based on these data we investigate potential spill over of ecosystem functions from forest into adjoining agroecosystems. For predation rates we found trends of spill over effects from forest interior into the agroecosystem. The expression of ecosystem functions differed among habitat types, with comparatively high predation rates in the forest, high pollinator activity in the open agricultural areas, and highest arthropod diversity along the forest edge. Eucalyptus plantations showed reduced ecosystem functions and lowest arthropod diversity. Local factors such as vegetation cover and flower supply positively influence pollinator activity. Our study show that natural ecosystems may positively contribute ecosystem functions such as predation, while the homogenization of biota through planting of invasive exotic tree species significantly reduce biodiversity and ecosystem functions. Transition habitats such as forest margins, and small-scale ecological enhancement positively influences biodiversity and ecosystem functions.

INVASIVE EXOTIC PLANT SPECIES AND THEIR INFLUENCE ON THE ENVIRONMENT, ECOSYSTEM SERVICES, ECONOMY AND HEALTH: A SEARCH

Invasive exotic plant species (IEPS) is recognized as threat to the native biodiversity and leads to the loss of habitat for the indigenous species on the earth. Invasions not only tear down the native plant species but have adverse impacts on economy and human health. Many documented records from Western countries connected with alien species revealed altered ecosystem services and socio-economic conditions via diverse mode of actions. Even though, the ecological impacts of alien species were documented, there is a dearth of analysis regarding their economic quantification, livelihood considerations, biotechnological aspects and human health risk assessments are the need of the hour. The noxious exotic invasive plants in India were Ageratum conyzoides, Eupatorium adenophorum, Parthenium hysterophorus, Lantana camara, Mikania micrantha, Argemone mexicana and Eichhornia crassipes. In this context, an attempt was made to enlist the alien species of Kerala and a review to account the impacts of invasive exotic plant species on various aspects of the environment globally. Results regarding the alien species search revealed the following species such as Chromolaena odorata, Senna spectabilis, Hypoestes sanguinolenta, Maesopsis eminii, Eupatorium cannabinum, Mikania micrantha, Sphagneticola trilobata and Acacia mearnsii were intruded in to various ecosystems of Kerala after the repeated floods. They directly affect the germination and survival of local species, damage the quality of soil and affect ground water availability. Nearly 80 species were noted as alien species in Kerala by many state level surveys. Research in the direction of impact of alien species on socio-economic cultural aspects of life and derailment of ecosystem is not yet seriously carried from Kerala. Further, there is a paucity of the ecological models/indicators to establish interrelationship among global environmental changes, biodiversity and health, warranting future researches.

Disturbance and indirect effects of climate warming support a plant invader in mountains

Climate warming and increased disturbance (resulting from intensified land use) are expected to enhance the invasibility of plant communities and the performance of exotic species also at high elevations, and thus pose additional threats to mountain ecosystems. The invasion success of introduced genotypes will also depend on their degree of pre‐adaption to high elevation climatic conditions, which may vary intra‐specifically across source populations. For populations currently spreading in the lowlands, climate warming might reduce the climatic distance to high‐elevation sites and thus remove a barrier to upwards spread.Here, we investigated the various facets of mountain invasions in a single, integrative experimental study. We applied a community transplant approach between high‐ and low‐elevation sites in the European Alps to address effects of climate warming and disturbance through land use on community invasibility and the performance of the exotic species Senecio inaequidens, a potential future plant invader in the Alps. Additionally, the transplant sites served as common gardens to test the influence of climatic pre‐adaptation to current (high site) and future (low site) climatic conditions on the performance of S. inaequidens in the transplanted communities. The 16 invasive central and western European S. inaequidens source population locations covered a wide geographic range, and thus a wide amplitude of climatic distances and presumed pre‐adaptation to our gardens.Our results attest to a strong effect of disturbance, which increased community invasibility, and promoted the performance of the exotic species. Contrary to our expectation, experimentally induced climate warming did not increase community invasibility. However, the performance of the S. inaequidens populations was positively related to their pre‐adaptation to the climatic conditions of our common gardens. Climate warming might thus promote the invasion of exotic species by reducing the climatic distance between mountain ranges and locations of potential source populations.

Distinct soil microbial communities under Ageratina adenophora invasions.

Ageratina adenophora is one of the most hazardous invasive weeds in China. It can form a single species community quickly and cause extensive ecological harm. The belowground microbial community can participate in nutrient transformation in soil and plays an important role in the invasiveness of exotic plant species. We selected sampling sites with different invasion levels of A. adenophora. The soil property and soil biogeochemical activity were measured in both bulk and rhizosphere soil under the aggressive weed A. adenophora and under adjacent native plants. The composition of bacterial communities was investigated using high-throughput 16S rRNA gene sequencing. We found that the rhizosphere habitat selectively accumulated Sphingomonas and Steroidobacter and reduced the abundance of Gaiella and Gp6 regardless of plant host. The presence of A. adenophora caused a switch in microbial composition from Aeromicrobium and Marmoricola to Reyranella and Bradyrhizobium in the bulk soil, and from Gp4, Pirellula, Lysobacter and Aridibacterrae to Reyranella and Streptomyces in the rhizosphere soil. We also revealed specific microbes that closely related with N-cycling processes. In addition, soil pH was the main factor affecting microbial communities in both bulk and rhizosphere soil. Our study confirmed that the rhizosphere environment imposed homogenous microbial communities. The invasion of A. adenophora selected specialized bacterial communities in soils and specific microbes that potentially mediated soil nutrition cycling. Our findings provide ecological explanation to explain how the underground microbes help A. adenophora invasive.