Effects of predation risk on pollinators and plants

Almost all pollination studies neglect the possible effects of predation on flower visitors. Various authors have even claimed that predation is too infrequent to influence pollinator behavior. It is tempting to dismiss the role of predation because it is rarely observed. In the past two decades, however, ecologists have learned to appreciate the central role that predation risk plays in animal behavior and ecology, mostly through a variety of measures animals take to minimize predation. Studies on a wide variety of animals from zooplankton to mammals have suggested that predation risk affects: diurnal patterns of activity; choice of diet, habitat, food patches, and food type; ways of handling food items; social organization; choice of nest sites; and various physiological factors such as diurnal and seasonal levels of fat reserves and respiration patterns (Price et al. 1980; Lawton 1986; Bernays & Graham 1988; Lima & Dill 1990; Clark 1993; Martin 1995; Lima 1998a, b; Ydenberg 1998). Are flower-visiting animals really immune to predation, or does the prevailing view about the unimportance of predation in pollination systems merely reflect researchers' inattention? In this chapter, I shall review some of the literature and argue that pollination ecologists have mostly overlooked a central factor influencing pollinator traits and pollination systems. Specifically, I ask: (1) Are there significant levels of predation on pollinators? (2) How might predation affect pollinator traits? And, (3) how might predation influence pollinator–plant interactions?