COS 134-6 - The effect of arbuscular mycorrhizal fungi from former mining sites on attractive plant traits, pollinator visitation, and plant fitness

Abstract: Mutualistic interactions with other organisms drive species’ ecological and evolutionary trajectories and can be crucial for plant survival in stressful environments. Plants engage with a variety of above- and below-ground mutualistic partners, including pollinators and arbuscular mycorrhizal (AM) fungi, respectively. These mutualisms can also influence each other; AM fungi can alter floral traits that function in pollinator attraction, but few studies have linked the impact of AM fungi to pollinator visitation and plant fitness. In addition, little is known about how plant-AM fungal and plant-pollinator mutualisms interact in environments with a history of anthropogenic disturbance. The Wilds is a conservation park in eastern Ohio located on formerly surface-mined land. Sites across The Wilds experienced different reclamation histories, from no improvement other than replanting to full grassland establishment, including the addition of topsoil. In a greenhouse study, we inoculated two perennial plant species (Clinopodium vulgare [wild basil], Mentha spicata [spearmint]) common at The Wilds that provide resources for pollinators throughout the growing season with AM fungal spores collected from sites with the different reclamation histories. The inocula from sites with less improvement contained fewer AM fungal spores and a less diverse AM fungal community relative to inocula from sites at The Wilds that experienced full grassland establishment. We aim to determine whether the AM fungi from the two site types differentially affect plant growth, flowering onset, flowers produced, flower size, nectar and pollen quantity and quality, pollinator visitation, and reproductive success. Our results indicate that AM fungi generally improve the growth and the ability of the plants to interact with pollinators because the plants of both species inoculated with AM fungi from either site at The Wilds grew taller, flowered earlier, and produced more flowers than the control plants. In addition, C. vulgare plants inoculated with AM fungi from sites with little reclamation history produced larger flowers than the control plants. However, bumble bees preferred C. vulgare plants inoculated with AM fungi from sites with a more comprehensive reclamation history over plants inoculated with AM fungi from sites with less reclamation history. Though we did not find an effect of AM fungi on the other attractive traits that we measured, our results have implications for plant fitness. They suggest that increased reclamation effort and the plant-AM fungal mutualism may help plant communities to recover following anthropogenic disturbance, support pollinators, and persist long-term, lending hope to the conservation potential of similar environments.