Influence of group size and floral display on pollinator behaviour in Moricandia arvensis

Abstract

Optimal foraging theory predicts that pollinators will visit dense floral patches over sparse ones. Understanding how the local abundance of floral resources influences pollinator behaviour is crucial for assessing the effect of floral traits on plant reproduction. In this study, we experimentally investigate the role of plant group size and floral display on pollinator foraging behaviour visiting Moricandia arvensis (Brassicaceae). We performed two field experiments: the first manipulated the number of plants per group (group size), and the second manipulated both the total number of flowers per group (group floral display) and group size. We then recorded the foraging behaviour of pollinators using probability of approaching the group, number of plants visited per group, bout length and floral visitation rate. Group floral display was the primary factor influencing pollinator foraging behaviour, except for the probability of approaching the group, where a significant interaction between group floral display and group size was observed. Specifically, the effect of larger floral displays on attracting pollinators increased disproportionately in larger groups. Because the increase in floral visitation rate due to larger displays was less than the increase in the floral display itself, visitation rate per flower was lower in groups with larger displays than in those with smaller displays. Although pollinator foraging behaviour depended largely on local floral resources, the number of plants per group partially shaped the effect of the group floral display on pollinator attraction and visitation rate. This interaction indicates complex effects of neighbouring floral traits on plant-pollinator interactions, which may have important consequences for mating patterns and plant reproductive success.