Understanding the influence of inflorescence position on plant-pollinator communities

Many factors influence the type of pollination utilized by flowering plants to accomplish genetic exchange.  In addition, specific guilds of pollinators are frequently associated or coevolved with taxonomic groups of plants to accomplish this task.  Of the various elements contributing to the floral syndromes of plants, position of floral inflorescence may affect the type of visitation a flower receives from insect pollinators, as well as the specific pollinator community associated with the plant.  Tomatoes are one crop plant that benefits from specific actions of pollinators referred to as buzz pollination.  The importance of floral inflorescence position was examined though direct manipulation of tomato flowers in a greenhouse situation and visitation response by Bombus impatiens.  Tomato flowers were positioned at angles of 0, 45, 90, 135, and 180 degrees with respect to vertical on artificial stakes.  In field situations, natural tomato blossoms were found to naturally exhibit an average position of 35 degrees with respect to vertical.  No differences could be detected between bee visitation and a floral position under greenhouse conditions.  We speculate that while tomatoes have evolved to benefit from buzz-pollination, this does not necessarily represent a two-way example of coevolution from the perspective of bumble bee behavior.