Corolla stickiness prevents nectar robbing in Erica

Area of Science:

• Botany
• Ecology
• Evolutionary Biology

Background:

• Floral stickiness is a rare trait with an unclear adaptive significance.
• The genus Erica (Ericaceae) exhibits a high prevalence of floral stickiness.
• Nectar robbing, where pollinators access nectar without providing pollination services, can negatively impact plant reproductive success.

Purpose of the Study:

• To investigate the role of floral stickiness in Erica as a defense mechanism against nectar robbing.
• To determine the correlation between floral stickiness and various floral traits.
• To understand the relationship between stickiness and pollination syndromes in Erica.

Main Methods:

• Experimental addition of stickiness to Erica flowers to assess its impact on nectar robbing.
• Comparison of nectar robbing incidence in natural communities with varying levels of floral stickiness.
• Statistical analysis of the correlation between stickiness and floral traits (pollination syndrome, corolla shape, length, sepal-corolla ratio) across the Erica genus.

Main Results:

• Floral stickiness was significantly correlated with lower rates of floral damage from nectar robbing, both within and between species.
• Stickiness in Erica is strongly associated with pollination by birds and long-proboscid flies, likely due to higher nectar rewards.
• Stickiness correlated with floral characteristics often exploited by nectar robbers, such as narrow corolla mouths, long corollas, and short sepals.

Conclusions:

• Corolla stickiness in Erica serves as an effective defense against nectar robbing.
• This anti-nectar robbing function of stickiness may contribute to improved plant fitness in Erica.
• The study highlights the adaptive value of floral stickiness in the context of specialized pollination interactions and herbivory pressure.