Nectar supplementation changes pollinator behaviour and pollination mode in Pedicularis dichotoma: implications for...

Area of Science:

• Evolutionary biology
• Plant reproductive strategies
• Pollination ecology

Background:

• Floral nectar evolution involves gains and losses across plant lineages.
• Reverse transitions, specifically nectar gain, lack clear explanations.
• The genus Pedicularis exhibits multiple nectar gains and losses.

Purpose of the Study:

• Investigate the causes of nectar gain in flowering plants.
• Determine how experimental nectar addition affects pollinator behavior in *Pedicularis dichotoma*.
• Understand the evolutionary implications of nectar gain in *Pedicularis*.

Main Methods:

• Quantified nectar presence and composition in *P. dichotoma*.
• Used high-performance liquid chromatography to analyze nectar sugars.
• Experimentally added artificial nectar to flowers to observe bumble-bee pollinator responses.

Main Results:

• A quarter of unmanipulated *P. dichotoma* flowers contained nectar (0.01-0.49 μL, 4-39% sugar).
• Nectar was sucrose-dominant, similar to sympatric *Pedicularis* species.
• Bumble-bees shifted from sternotribic pollen collection to nototribic nectar foraging in nectar-supplemented flowers, decreasing sternotribic pollination.

Conclusions:

• This study quantifies nectar variation in a 'nectarless' *Pedicularis* species.
• Experimental nectar addition induced rapid adaptive behavioral shifts in pollinators.
• Nectar gain in *Pedicularis* likely enhances pollinator attraction in variable environments.