Pollinator Foraging, Experimental Nectar-robbing and Plant Fitness in Impatiens capensis

Abstract

Bombus vagans workers were observed collecting nectar from 2 populations of I. capensis. Approximately 1/2 of the flowers in 2 population had their standing crops of nectar removed in a manner simulating nectar-robbing by bumblebees. The other population seved as a control. B. vagans employed area-restricted searching behavior in both populations. The increased frequency of long-distance bee flights associated with the abundant low-quality reward blossoms in the nectar-robbed patch served to increase neighborhood size relative to the control area. Pollen was transported greater distances because of nectar thievery, thus making it more likely that the main purpose (i.e., genetic varibaility via outbreeding) of the chasmogamous flowers of I. capensis was achieved. Because seed set was statistically indistinguishable for robbed and unrobbed blossoms, nectar-robbing may thus actually enhance female fitness in I. capensis.