Microplastics clog reproduction in a monkeyflower species

Summary Plastic debris is a widespread and significant marker of global change, found in all ecosystems and overpassing the total animal biomass on the whole planet. Despite its ubiquity, our knowledge of its potential effects on terrestrial organisms and ecological processes is still limited. Recently, a study showed that honey bee Apis mellifera transport microplastics (MP; plastic fragments <5 mm) that are added to their bodies. Additionally, a report showed that MP has the potential to reach plant ovules. These findings suggest that pollinators may inadvertently deposit MP on flower stigmas, which could impact the reproductive output of plants. We assessed whether small polypropylene fragments (<63 μm) deposited on the stigmas decrease pollen tube development, seed production, seed mass, and germination in the Andean-yellow monkeyflower Erythranthe lutea (Phrymaceae). Using a mix of hand-pollination treatments and ultrastructure observation, we showed that the MP deposit has a negative impact on seed production and the number of pollen tubes that reached ovaries. However, mass per seed and germination of the resulting seeds were not affected. Our findings warn about the deleterious effects of synthetic plastic on a critical ecosystem process, pollination, and suggest that MP could have significant consequences for angiosperms and crop production.