Does pollination limit tolerance to browsing in Ipomopsis aggregata?

Area of Science:

• Ecology
• Plant Biology
• Herbivory Studies

Background:

• Ungulate browsing on the herb Ipomopsis aggregata can lead to variable plant reproductive success, with outcomes ranging from overcompensation to undercompensation.
• The mechanisms driving this variable tolerance to herbivory remain poorly understood, particularly concerning the role of pollination dynamics.

Purpose of the Study:

• To investigate whether variations in pollination success mediate the tolerance of Ipomopsis aggregata to ungulate browsing.
• To explore the direct impacts of browsing on plant resource allocation and regrowth capabilities.

Main Methods:

• Simulated ungulate browsing by clipping inflorescences of Ipomopsis aggregata to assess effects on floral display, branching, and phenology.
• Observed pollinator (hummingbirds) and nectar-robber (bumblebees) visitation rates on clipped versus unclipped plants.
• Conducted hand-pollination experiments to determine the role of pollen limitation in plant compensation.

Main Results:

• Clipping reduced floral display size and increased branching but did not alter pollinator preference.
• Phenological shifts due to clipping altered plant-pollinator overlap and visitation rates across years.
• Clipped plants exhibited severe undercompensation in seed production, irrespective of supplemental pollination, indicating resource limitation.

Conclusions:

• Plant tolerance to browsing is primarily constrained by direct impacts on resource availability for regrowth and seed provisioning, rather than indirect effects on pollination.
• Future research should focus on the physiological and developmental processes governing inflorescence regrowth and seed development to understand variation in herbivory tolerance.