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Purpose: Cheatgrass invasion of Intermountain sagebrush steppe in the western United States poses increasing challenges to the function and survival of this native ecosystem. The invasive success and persistence of cheatgrass has been attributed to the increasing soil total nitrogen, but mechanisms behind remain inconclusive. We hypothesized that soil microorganisms play a role in soil nitrogen associated with cheatgrass invasion. Methods: We collected soil samples from the root zone of cheatgrass, native bunchgrass, and sagebrush at two depths and from two adjacent sites in April. We examined soil chemical properties (pH, moisture content, and NH4+ and NO3− concentration) and soil microbial communities. Results: We found that cheatgrass invasion was associated with different soil microbial community composition compared to native bunchgrass and sagebrush. In particular, we observed higher relative abundances of N2 fixers and ureolytic bacteria and lower relative abundance of denitrifiers providing a potential mechanistic belowground explanation of raising soil nitrogen. Conclusions: Overall, our results indicate the importance of soil microorganisms in the dominance and persistence of invasive species. Targeted microbiome interventions should be considered to control cheatgrass invasion. [ABSTRACT FROM AUTHOR]

Aim Large-scale distributions of plants and animals have been studied extensively and form the foundation for core concepts and paradigms in biogeography and macroecology. Much less attention has been given to other groups of organisms, particularly obligate symbiotic organisms. We present the first quantitative assessment of how spatial and environmental variables shape the abundance and distribution of obligate symbiotic organisms across nearly an entire subcontinent, using lichen propagules as an example. Location The contiguous United States (excluding Alaska and Hawaii). Methods We use DNA sequence-based analyses of lichen reproductive propagules from settled dust samples collected from nearly 1300 home exteriors to reconstruct biogeographical correlates of lichen taxonomic and functional diversity. Results Contrary to expectations, we found a weak but significant reverse latitudinal gradient in lichen propagule diversity. Diversity was not impacted by urbanization or human population density. We show that propagules of asexually reproducing species have wider geographical ranges than propagules from sexually reproducing species, likely reflecting the lichenized nature of asexual spores that disperse both the mycobiont and photobiont versus non-lichenized sexual spores, which disperse only the mycobiont. Main Conclusions Our findings of a reverse latitudinal gradient and a relative lack of impact of urbanization on lichen propagules and/or lichen-forming fungal spores suggest that core concepts in biogeography are better informed via consideration of additional patterns from other, less well studied groups of organisms. [ABSTRACT FROM AUTHOR]

We spend the majority of our lives indoors; yet, we currently lack a comprehensive understanding of how the microbial communities found in homes vary across broad geographical regions and what factors are most important in shaping the types of microorganisms found inside homes. Here, we investigated the fungal and bacterial communities found in settled dust collected from inside and outside approximately 1200 homes located across the continental US, homes that represent a broad range of home designs and span many climatic zones. Indoor and outdoor dust samples harboured distinct microbial communities, but these differences were larger for bacteria than for fungi with most indoor fungi originating outside the home. Indoor fungal communities and the distribution of potential allergens varied predictably across climate and geographical regions; where you live determines what fungi live with you inside your home. By contrast, bacterial communities in indoor dust were more strongly influenced by the number and types of occupants living in the homes. In particular, the female : male ratio and whether a house had pets had a significant influence on the types of bacteria found inside our homes highlighting that who you live with determines what bacteria are found inside your home.