Soil Microbes Alter the Diversity-Invasibility Relationship by Promoting a Complementarity Effect on Community Invasion Resistance

Background Soil microbes can affect both the invasiveness of exotic plants and the invasibility of native plant communities, but it still remains unclear whether soil microbes can influence the relationship between native plant diversity and community invasibility.Methods We constructed native plant communities with three levels of species richness (one, three, or six species) in unsterilized or sterilized soil (i.e., with or without soil microbes) and either prevented their invasion by exotic plants or allowed them to be invaded by each of three exotic species (Solidago canadensis, Erigeron canadensis or Symphyotrichum subulatum), which are highly invasive in China. The soils conditioned by the native plant communities that were not invaded by the exotic species were used as soil microbe inocula to test whether species richness-induced differences in soil microbes affected the growth of each of the three invasive species.Results Compared with soils containing microbes, the absence of soil microbes weakened the negative species richness-invasibility relationship, indicating that soil microbes can contribute to higher invasion resistance in more diverse native plant communities. In the presence of soil microbes, the higher invasion resistance of more diverse communities was mainly ascribed to the complementarity effect. However, soil microbes from communities with a higher species richness did not have a stronger negative effect on the growth of any of the three invasive species. Conclusion Soil microbes can alter the diversity-invasibility relationship by promoting the complementarity effect on community invasion resistance. Our results highlight the importance of integrating the role of soil microbes when testing the diversity-invasibility hypothesis.

Role of Endophytes and Rhizosphere Microbes in Promoting the Invasion of Exotic Plants in Arid and Semi-Arid Areas: A Review

Endophytes and rhizospheric microorganisms support invasive species’ adaptation to environmental stresses. Here, we review the impacts of endophytes, rhizospheric microbes (particularly symbiotic nitrogen-fixers), mycorrhiza and pathogens on plant invasion in arid and semi-arid areas. Endophytes and soil microorganisms either enhance nutrient acquisition for enhancing the invasive plant immune system and/or negatively affect native plants. In addition, the positive feedback between mycorrhizal fungi and invasive plants enhances the competitive ability of the aliens, providing them more opportunities for success, establishment, and dominance. The microbes and their secondary metabolites promote invasive plant species by changing soil microbial community structure and carbon biomass as well as enzyme activity, which improves soil properties and processes. The negative impact of invasive exotic plants on the associated biota and the role of allelochemicals are also discussed. It could be concluded that endophytes interact with rhizosphere microbes to promote invasive plant species in arid and semi-arid areas in a way similar to what happens in other ecosystems; the differences are in the pathways and reactions, which depend upon the prevailing abiotic factors. More interdisciplinary field experiments integrating microbial, biotechnological, and molecular approaches are needed to understand the role of symbiotic microbes in invasion biology.

Mexican Coastal Dunes: Recipients and Donors of Alien Flora

The invasion of natural communities by exotic plants, which may turn into invasive or potentially invasive, is one of the most severe known threats to biodiversity, and coastal dunes are among the most affected habitats. Mexico’s coastal dunes are abundant and contain high plant biodiversity but attempts to determine the occurrence and impact of exotic plants are absent. First, we explored the number of invasive plant species found on Mexican coastal dunes. Second, we analyzed if the coastal dune flora native from Mexico acts as a source of invasive species worldwide. We found the relevant spread of exotic plants towards and from Mexico, reaching high percentages: 5% of the coastal dune flora are considered exotic plants; this increases to 8.7% when only plants typical of the coastal dune environment are considered. The Mexican coastal dunes flora is also a relevant source of invasive plants affecting all continents. Furthermore, almost half of the 35 worst worldwide invasive plants (according to the Global Invasive Species Database GISD) grow on Mexican coastal dunes, most native to Mexico and invasive elsewhere. Indeed, the worldwide exchange of coastal dune flora between Mexico and the world seems massive, relevant and highlights the need for worldwide and countrywide management and control strategies.

Levoglucosan Emission From Different Indigenous and Exotic Plant Species in Bangladesh

Levoglucosan is a biomarker for biomass burning with high emission efficiency. Both indigenous and exotic plant species (biomass) are common in Bangladesh and used as a fuel source in rural areas for cooking purposes. Three indigenous plants, Mango (Mangifera indica), Jackfruit (Artocarpus heterophyllus), Coconut (Cocos nucifera) and three exotic plants, Mahogany (Swietenia mahagoni), Koroi (Albizia lebbeck), Guava (Psidium guajava), were selected for this experiment. The study was carried out to determine and compare the levoglucosan emission for these selected indigenous and exotic plants upon burning at the typical rural cooking stove in the laboratory scale. PM10 samples were collected on top of the cooking stove using a low volume air sampler (LVAS). The concentration was determined quantitatively by UV-visible spectrophotometer using anthrone-sulfuric acid reagent. The exotic plant samples (7.47 mg/m3) emitted a higher concentration of levoglucosan than the indigenous plant samples (6.49 mg/m3). Among the six different leaf samples, S. mahagoni leaves showed the highest emission of levoglucosan (6.31 mg/m3) and C. nucifera leaves showed the lowest levoglucosan (5.74 mg/m3) due to their individual cellulose content and combustion efficiency. Among the six wood samples, S. mahagoni woods showed the maximum concentration (9.63 mg/m3) and C. nucifera coir showed the minimum concentration (6.631 mg/m3) of levoglucosan emission. The soft leaf samples (6.02 mg/m3) showed lower emission than the hardwood (7.97 mg/m3) samples because of their diverse structural pattern and combustion efficiency. Comparing the emission factors, the exotic wood and leaf samples (EF=2.89*10– 3g/kg) showed higher emission than the indigenous wood and leaf samples (EF=2.55*10–3g/kg) J. Biodivers. Conserv. Bioresour. Manag. 2020, 6(2): 1-10

Ação dos extratos de favela (Cnidoscolus phyllacanthus), catingueira (Caesalpinia pyramidalis) e nim (Azadiracta indica) sobre bactérias isoladas de cabras de aptidão leiteira

RESUMO No Nordeste brasileiro, cuja vegetação predominante é Caatinga, muitas plantas nativas ou exóticas são potencialmente ricas em propriedades curativas, porém pouco exploradas ainda pela ciência. O trabalho foi realizado durante agosto de 2011 a junho de 2012, onde foram coletadas amostras bacterianas dos tetos dos animais através de swabs estéreis. Isolados e devidamente identificados, os microrganismos foram sujeitos a antibiogramas com os meios alternativos, controles positivos e negativo através da técnica de difusão em Ágar de poço. O objetivo do trabalho foi avaliar a ação dos extratos de Favela (Cnidoscolus phyllacanthus), Catingueira (Caesalpinia pyramidalis) e Nim (Azadiracta indica) sobre bactérias isoladas de tetos de cabras no assentamento de Cordão de Sombra no Município de Mossoró-RN. ABSTRACT In Northeast Brazil, whose predominant vegetation is Caatinga, many native or exotic plants are potentially rich in healing properties, but little explored yet by science. The work was conducted during August 2011 to June 2012, where bacterial samples were collected from the teats of animals through sterile swabs. Once isolated and properly identified, the microorganisms were subjected to antibiograms with alternative means, positive and negative controls through the well agar diffusion technique. The objective of the work was to evaluate the action of extracts of Favela (Cnidoscolus phyllacanthus), Catingueira (Caesalpinia pyramidalis) and Neem (Azadiracta indica) on bacteria isolated from teats of goats in the settlement Cordão de Sombra in the Municipality of Mossoró-RN.

Exotic plants accumulate and share herbivores yet dominate communities via rapid growth

Herbivores may facilitate or impede exotic plant invasion, depending on their direct and indirect interactions with exotic plants relative to co-occurring natives. However, previous studies investigating direct effects have mostly used pairwise native-exotic comparisons with few enemies, reached conflicting conclusions, and largely overlooked indirect interactions such as apparent competition. Here, we ask whether native and exotic plants differ in their interactions with invertebrate herbivores. We manipulate and measure plant-herbivore and plant-soil biota interactions in 160 experimental mesocosm communities to test several invasion hypotheses. We find that compared with natives, exotic plants support higher herbivore diversity and biomass, and experience larger proportional biomass reductions from herbivory, regardless of whether specialist soil biota are present. Yet, exotics consistently dominate community biomass, likely due to their fast growth rates rather than strong potential to exert apparent competition on neighbors. We conclude that polyphagous invertebrate herbivores are unlikely to play significant direct or indirect roles in mediating plant invasions, especially for fast-growing exotic plants.

Asymmetric pathogen spillover favors exotic plants over natives

Exotic plants can escape from specialist pathogenic microorganisms in their new range, but may simultaneously accumulate generalist pathogens. This creates the potential for pathogen spillover, which could alter plant-competitive hierarchies via apparent competition. To assess the potential for and consequences of pathogen spillover in invaded communities, we conducted a community-level plant-soil feedback experiment in experimental communities that ranged in the extent of exotic dominance, using next-generation sequencing to characterize sharing of putatively-pathogenic, root-associated fungi (hereafter, ‘pathogens’). Exotic plants outperformed natives in communities, despite being subject to stronger negative plant-soil feedbacks in monoculture and harboring higher relative abundance of pathogens. Exotic plants made more general associations with pathogens, making them more prone to sharing pathogens with natives and exerting apparent competition. These data suggest that exotic plants accumulate generalist pathogens that are shared with native plants, conferring an indirect benefit to exotic, over native plants.