Flowering plant density and pollinator visitation in Senecio

Area of Science:

• Ecology
• Plant-pollinator interactions
• Behavioral ecology

Background:

• It is often assumed that higher flowering plant density leads to increased pollinator energy intake and flower visitation.
• This assumption suggests that denser stands should experience higher pollinator activity.

Purpose of the Study:

• To investigate the relationship between flight distance and flight time for bumblebees and butterflies foraging on Senecio species.
• To compare pollinator visitation patterns and seed set in experimentally thinned versus natural density plots of Senecio integerrimus.

Main Methods:

• Field study in the Colorado Rocky Mountains examining bumblebee and butterfly foraging behavior on Senecio.
• Experimental manipulation of flowering plant density in S. integerrimus plots (thinned vs. natural density).
• Measurement of flight distance, flight time, visitation rates, plant characteristics, and seed set.

Main Results:

• Plant density did not affect pollinator visitation rates, although pollinators were more selective in denser plots.
• Visitation rates varied seasonally, peaking during peak flowering.
• Plant density and inflorescence size had no significant effect on seed production.

Conclusions:

• Flowering phenology and pollinator foraging behavior differences are more critical for Senecio seed set and gene flow than plant density or size.
• The assumed relationship between plant density and pollinator intake may not hold true in this system.