Microplastic exposure modulates the impacts of genotypic richness and evenness on population performance of...

Genetic diversity within plant populations is a key determinant of ecosystem functioning, especially, in shaping plant productivity. However, existing research examining how genetic diversity influences productivity has primarily focused on genotypic richness (number of genotypes), leaving the role of genotypic evenness (relative abundance of genotypes) understudied. Moreover, while microplastics has become a widespread contaminant, it is unknown whether microplastics could influence the impact of genetic diversity on plant growth performance. To address these gaps, we conducted an experiment using the clonal plant Hydrocotyle verticillata, manipulating both genotypic richness (1, 3, 6) and genotypic evenness (low, medium, high), crossing treatments with three types of soil microplastics (polylactic acid (PLA), poly-3-hydroxybutyrate (PHB) and polybutylene succinate (PBS)) and a control group without microplastics. All three microplastics significantly decreased biomass of H. verticillata. Genotypic richness had no effects on biomass, however, its effect on ramet numbers was altered by microplastics. The effect of genotypic evenness on both biomass and ramets were regulated by microplastics. With PBS, H. verticillata with high genotypic evenness produced significantly lower biomass and ramet numbers than those with low or medium evenness. However, this pattern was not observed under the PHB or PLA treatments. The study concludes that microplastics can modulate the effects of genotypic richness and evenness on the population performance of H. verticillata, but the effects vary depending on the type of microplastics. Our findings highlight the role of microplastics in regulating biodiversity-productivity relationships.