Foraging behavior and pollination efficiency of generalist insects in an understory dioecious shrubHelwingia japonica

Abstract

It has been hypothesized that pollination success in animal-pollinated dioecious plants relies on opportunistic pollinators with no discrimination against female flowers. However, empirical studies of pollinator foraging behavior and pollination effectiveness in dioecious species are few. METHODS: To investigate potential pollinators in Helwingia japonica, a dioecious shrub with small, inconspicuous flowers, we compared floral visitors and visit frequency to female and male plants for three flowering seasons in two field populations in subtropical forests in southwest China. Pollen placement on the insect bodies of four groups (solitary bees and other bees, fungus gnats, and other flies) was compared, and insect foraging behavior was observed. Pollen removal and conspecific and heterospecific pollen deposition per visit were measured to compare pollination effectiveness among the four groups. RESULTS: Floral visitors usually did not discriminate between male and female flowers and did not gather pollen into collections. Our measurements of pollen transfer efficiency showed that solitary bees were the most effective pollinators with the highest conspecific pollen deposition. These insects seemed to be opportunistic visitors because pollen grains of H. japonica were distributed evenly over different regions of the visitor's body, and heterospecific pollen accounted for over 50% of total pollen loads on stigmas in the two populations. CONCLUSIONS: Our investigations indicated that potential pollinators were generalists and did not discriminate against female flowers, as predicted for dioecious species pollinated by insects. A perspective of pollen removal by floral visitors offers insights into the evolution of plant sexual systems.

Comparison of Pollen-Collecting Abilities between Apis mellifera L. and Bombus terrestris L. in the Oil Tree Peony Field

“…In the study of potential pollinators in an understory dioecious shrub (Helwingia japonica Thunb. F. Dietr), the pollens were distributed evenly on a different part of their bodies [48]. However, the pollen placement on the different parts of bees was significantly different in our study, which makes the phenomenon may be related to the behavior of grooming pollen.…”

What Are the Best Pollinator Candidates for Camellia oleifera: Do Not Forget Hoverflies and Flies

“…To identify the visiting insects, we photographed those that sat on the C. oleifera flowers and used a sweep net for capture. The insects captured were stored in 10 mL vials containing 75% alcohol and were then transported to the laboratory for identification by the relevant experts [ 18 ].…”