The function-dominance correlation drives the direction and strength of biodiversity-ecosystem functioning relationships.

Community composition is a primary determinant of how biodiversity change influences ecosystem functioning and, therefore, the relationship between biodiversity and ecosystem functioning (BEF). We examine the consequences of community composition across six structurally realistic plant community models. We find that a positive correlation between species' functioning in monoculture versus their dominance in mixture with regard to a specific function (the "function-dominance correlation") generates a positive relationship between realised diversity and ecosystem functioning across species richness treatments. However, because realised diversity declines when few species dominate, a positive function-dominance correlation generates a negative relationship between realised diversity and ecosystem functioning within species richness treatments. Removing seed inflow strengthens the link between the function-dominance correlation and BEF relationships across species richness treatments but weakens it within them. These results suggest that changes in species' identities in a local species pool may more strongly affect ecosystem functioning than changes in species richness.

While shoot herbivores reduce, root herbivores increase nutrient enrichment's impact on diversity in a grassland model.

Nutrient enrichment is widespread throughout grassland systems and expected to increase during the Anthropocene. Trophic interactions, like aboveground herbivory, have been shown to mitigate its effect on plant diversity. Belowground herbivory may also impact these habitats' response to nutrient enrichment, but its influence is much less understood, and likely to depend on factors such as the herbivores' preference for dominant species and the symmetry of belowground competition. If preferential toward the dominant, fastest growing species, root herbivores may reduce these species' relative fitness and support diversity during nutrient enrichment. However, as plant competition belowground is commonly considered to be symmetric, root herbivores may be less impactful than shoot herbivores because they do not reduce any competitive asymmetry between the dominant and subordinate plants. To better understand this system, we used an established, two-layer, grassland community model to run a full-factorially designed simulation experiment, crossing the complete removal of aboveground herbivores and belowground herbivores with nutrient enrichment. After 100 yr of simulation, we analyzed communities' diversity, competition on the individual level, as well as their resistance and recovery. The model reproduced both observed general effects of nutrient enrichment in grasslands and the short-term trends of specific experiments. We found that belowground herbivores exacerbate the negative influence of nutrient enrichment on Shannon diversity within our model grasslands, while aboveground herbivores mitigate its effect. Indeed, data on individuals' above- and belowground resource uptake reveals that root herbivory reduces resource limitation belowground. As with nutrient enrichment, this shifts competition aboveground. Since shoot competition is asymmetric, with larger, taller individuals gathering disproportionate resources compared to their smaller, shorter counterparts, this shift promotes the exclusion of the smallest species. While increasing the root herbivores' preferences toward dominant species lessens their negative impact, at best they are only mildly advantageous, and they do very little reduce the negative consequences of nutrient enrichment. Because our model's belowground competition is symmetric, we hypothesize that root herbivores may be beneficial when root competition is asymmetric. Future research into belowground herbivory should account for the nature of competition belowground to better understand the herbivores' true influence.

Prevalence and epidemiological associates of novel psychedelic use in the United States adult population.

BACKGROUND: Novel psychedelics approximate classic psychedelics, but unlike classic psychedelics, novel psychedelics have been used by humans for a shorter period of time, with fewer data available on these substances. AIMS: The purpose of this study was to determine the prevalence of novel psychedelic use and the associations of novel psychedelic use with mental health outcomes. METHODS: We estimated the prevalence of self-reported, write-in lifetime novel psychedelic use and evaluated the associations of novel psychedelic use with psychosocial characteristics, past month psychological distress, and past year suicidality among adult respondents pooled from years 2008-2016 of the National Survey on Drug Use and Health (weighted n=234,914,788). RESULTS: A fraction (weighted n=273,720; 0.12%) reported lifetime novel psychedelic use. This cohort tended to be younger, male, and White, have greater educational attainment but less income, be more likely to have never been married, engage in self-reported risky behavior, and report lifetime illicit use of other drugs, particularly classic psychedelics (96.9%). (2-(4-Bromo-2,5-dimethoxyphenyl)ethanamine) (2C-B) (30.01%), (2,5-dimethoxy-4-iodophenethylamine) (2C-I) (23.9%), and (1-(2,5-dimethoxy-4-ethylphenyl)-2-aminoethane) (2C-E) (14.8%) accounted for the majority of lifetime novel psychedelic use. Although lifetime novel psychedelic use was not associated with psychological distress or suicidality compared to no lifetime novel psychedelic use or classic psychedelic use, relative to lifetime use of classic psychedelics but not novel psychedelics, lifetime novel psychedelic use was associated with a greater likelihood of past year suicidal thinking (adjusted Odds Ratio (aOR)=1.4 (1.1-1.9)) and past year suicidal planning (aOR=1.6 (1.1-2.4)). CONCLUSION: Novel psychedelics may differ from classic psychedelics in meaningful ways, though additional, directed research is needed.