There is more to pollinator-mediated selection than pollen limitation

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Spatial variation in pollinator-mediated selection (Δβpoll) is crucial for floral diversification.
• Quantitative links between Δβpoll, pollen limitation (PL), and net selection on floral traits remain unclear.

Purpose of the Study:

• To quantify the relationship between spatiotemporal variation in Δβpoll and net selection on floral traits.
• To investigate the influence of pollen limitation on pollinator-mediated selection in orchids.

Main Methods:

• Quantified Δβpoll on floral traits over 2-5 years in two orchid species with contrasting PL levels.
• Analyzed spatiotemporal variation in selection across populations.

Main Results:

• Spatiotemporal variation in Δβpoll explained significant variation in net selection for both species.
• Selection was stronger and more pollinator-mediated in a deceptive, pollen-limited orchid compared to a rewarding species.
• Pollen limitation did not explain variation in Δβpoll within species, suggesting trait-pollination success relationships are key.

Conclusions:

• Pollinator-mediated selection is a significant driver of net selection on floral traits.
• The functional relationship between floral traits and pollination success, rather than pollen limitation itself, largely governs variation in pollinator-mediated selection.
• Understanding spatiotemporal selection requires disentangling interaction intensity and trait functional significance.