Increased Leaf Bacterial Network Complexity along the Native Plant Diversity Gradient Facilitates Plant Invasion?

Understanding the mechanisms of biological invasion is critical to biodiversity protection. Previous studies have produced inconsistent relationships between native species richness and invasibility, referred to as the invasion paradox. Although facilitative interactions among species have been proposed to explain the non-negative diversity-invasibility relationship, little is known about the facilitation of plant-associated microbes in invasions. We established a two-year field biodiversity experiment with a native plant species richness gradient (1, 2, 4, or 8 species) and analyzed the effects of community structure and network complexity of leaf bacteria on invasion success. Our results indicated a positive relationship between invasibility and network complexity of leaf bacteria of the invader. Consistent with previous studies, we also found that native plant species richness increased the leaf bacterial diversity and network complexity. Moreover, the results of the leaf bacteria community assembly of the invader suggested that the complex bacteria community resulted from higher native diversity rather than higher invader biomass. We concluded that increased leaf bacterial network complexity along the native plant diversity gradient likely facilitated plant invasion. Our findings provided evidence of a potential mechanism by which microbes may affect the plant community invasibility, hopefully helping to explain the non-negative relationship between native diversity and invasibility.

A comprehensive synthesis unveils the mysteries of phosphate-solubilizing microbes.

Phosphate-solubilizing microbes (PSMs) drive the biogeochemical cycling of phosphorus (P) and hold promise for sustainable agriculture. However, their global distribution, overall diversity and application potential remain unknown. Here, we present the first synthesis of their biogeography, diversity and utility, employing data from 399 papers published between 1981 and 2017, the results of a nationwide field survey in China consisting of 367 soil samples, and a genetic analysis of 12986 genome-sequenced prokaryotic strains. We show that at continental to global scales, the population density of PSMs in environmental samples is correlated with total P rather than pH. Remarkably, positive relationships exist between the population density of soil PSMs and available P, nitrate-nitrogen and dissolved organic carbon in soil, reflecting functional couplings between PSMs and microbes driving biogeochemical cycles of nitrogen and carbon. More than 2704 strains affiliated with at least nine archaeal, 88 fungal and 336 bacterial species were reported as PSMs. Only 2.59% of these strains have been tested for their efficiencies in improving crop growth or yield under field conditions, providing evidence that PSMs are more likely to exert positive effects on wheat growing in alkaline P-deficient soils. Our systematic genetic analysis reveals five promising PSM genera deserving much more attention.