|Although many plant communities are invaded by multiple nonnative species, we have limited
information on how a species’ origin affects ecosystem function. We tested how differences
in species richness and origin affect productivity and seedling establishment. We created phylogenetically paired native and nonnative plant communities in a glasshouse experiment to test diversity–productivity relationships and responsible mechanisms (i.e. selection
or complementarity effects). Additionally, we tested how productivity and associated
mechanisms influenced seedling establishment. We used diversity-interaction models to
describe how species’ interactions influenced diversity–productivity relationships.
Communities with more species had higher total biomass than did monoculture communities,
but native and nonnative communities diverged in root : shoot ratios and the mechanism
responsible for increased productivity: positive selection effect in nonnative communities and
positive complementarity effect in native communities. Seedling establishment was 46%
lower in nonnative than in native communities and was correlated with the average selection
effect. Interspecific interactions contributed to productivity patterns, but the specific types of
interactions differed between native and nonnative communities.
These results reinforce findings that the diversity–productivity mechanisms in native and
nonnative communities differ and are the first to show that these mechanisms can influence
seedling establishment and that different types of interactions influence diversity–productivity