Below-ground competition alters attractiveness of an insect-pollinated plant to pollinators. Issue 4 (12th June 2020)

• Record Type: Journal Article
• Authors: Flacher, Floriane; Raynaud, Xavier; Hansart, Amandine; Geslin, Benoît; Motard, Eric; Verstraet, Séléné; Bataille, Manon; Dajoz, Isabelle
• Editors: Arceo-Gómez, Gerardo
• Is Part Of: AoB plants. Volume 12:Issue 4(2020)
• Publication Date: 2020-06-12
• Subjects: Below-ground competition -- floral display size -- flower visitors -- Holcus lanatus -- pollination -- Sinapis alba; Plants -- Periodicals; Botany -- Periodicals; 580.5
• DOI: 10.1093/aobpla/plaa022
• Languages: English
• ISSNs: 2041-2851

Abstract

Abstract: Competitive interactions between plants can affect patterns of allocation to reproductive structures through modulation of resource availability. As floral traits involved in plant attractiveness to pollinators can be sensitive to these resources, competition with any neighbouring species may influence the attractiveness of insect-pollinated plants. While pollination research has primarily focused on above-ground interactions, this study aims at investigating if the presence of a competitor plant can modulate neighbouring insect-pollinated plant attractiveness to pollinators and resulting fecundity, especially through below-ground competitive interactions for soil resources. We set up a plot experiment in which we grew an insect-pollinated plant, Sinapis alba (Brassicaceae), in a mixture dominated by a wind-pollinated plant, Holcus lanatus (Poaceae). Individuals of S. alba were either subjected to or isolated from (with buried tubes in the soil) below-ground competition. Across the flowering season, floral traits involved in attractiveness of S. alba and pollinator visitation were followed at the plot and plant level to investigate different scales of attractiveness. At the end of the experiment, seeds were harvested to assess plant fecundity. Competition had a significant negative effect on plot and plant floral display size as well as flower size while nectar traits were not affected. When plants of S. alba were in competition, the time to first visit was altered: the proportion of plots that received a visit was smaller for a given time; in other words, it took more time for a given proportion of plots to be visited and some plots were even never visited. Moreover, pollinators made fewer visits per plots. The proportion of viable seeds produced by S. alba in competition was lower and probably linked to the competition itself rather than changes in pollinator visitation. This study suggests that competitive interactions between plants can modulate pollination interactions even when competing plant species are not insect-pollinated. Abstract : Through a plot experiment, this study shows that the presence of a competitor plant can modulate neighbouring insect-pollinated plant attractiveness to pollinators through below-ground competition for soil resources. Several floral traits as well as pollinator visitations were negatively influenced in condition of competition. A decrease of plant fecundity was also observed but probably linked to the competition itself rather than changes in pollinator visitation induced by competition. Still, this study suggests that, in a plant mixture, the presence of any competitor plant may influence plant–pollinator interactions and future studies on pollination should benefit from considering the whole plant community.