Data from: Genotypic diversity mitigates negative effects of density on plant performance: a field experiment and life-cycle analysis of common evening primrose Oenothera biennis

1.Genotypic diversity in plant populations is known to enhance plant
performance and ecosystem function. Nonetheless, the effect of genotypic
diversity has rarely been examined across a population's lifecycle
despite the expectation that changing conditions, such as population
density, will alter the benefits of diversity. 2.We simultaneously
manipulated a component of genotypic diversity (richness, the number of
genotypes) and density of common evening primrose Oenothera biennis to
address the consequences for herbivory and lifetime fitness in a two-year
field experiment that spanned seed germination to life-time fruit
production. We genotyped >1100 seedlings with microsatellite DNA
markers to determine realized diversity and density in plots sown with
O.biennis seeds. Our design achieved quantitative variation in plant
density and diversity, with one to 44 individuals established in field
plots and two to eight genotypes per polyculture plot (based on
microsatellite analysis of reproductive plants). 3.We found a strong
interaction between seed density and genetic diversity, with germination
and establishment being 24% higher in genetic polycultures than
monocultures, but only at low seed density. At high seed density, the
opposite pattern emerged, with polycultures having 12% fewer individuals
established than monocultures. Initial effects of emergence on plot
density persisted through to the fruiting stage. 4.Higher plant densities
result in increased mortality, decreased probability of reproduction,
decreased plant height, and lower levels of life-time fruit production per
plant. Increasing genotypic diversity increased the probability of
reproduction overall, and showed a significant interaction with plant
density mitigating the negative effects of high density on individual
height and lifetime fruit production. 5.Synthesis. Plant density and
genotypic diversity interacted from the very earliest stages of seed
germination and establishment of O. biennis. This effect persisted over
the two-year life-cycle of plants, and genotypic diversity buffered
against the negative fitness consequences of high plant density. These
results imply a dynamic interplay between the long-held paradigm of
density effects in plant ecology and the genetic structure of populations.