Nectar and floral morphology differ in evolutionary potential in novel pollination environments.

Area of Science:

• Evolutionary biology
• Plant reproductive strategies
• Floral trait evolution

Background:

• Floral traits evolve in response to pollinator changes, but the evolution of different traits can vary.
• Morphological traits are often integrated for pollination accuracy, while nectar traits may be more sensitive to environmental factors.
• The interplay of genetic correlations and phenotypic plasticity (PP) in floral evolution, especially for nectar, is not fully understood.

Purpose of the Study:

• To investigate the differential evolution of floral morphology and nectar traits in Digitalis purpurea.
• To compare phenotypic plasticity (PP), heritability, evolvability, and integration of floral morphology and nectar.
• To understand how intrafloral modularity influences the evolutionary potential of different floral traits.

Main Methods:

• Common garden experiment comparing PP, heritability, evolvability, and integration.
• Analysis of floral morphology and nectar traits in Digitalis purpurea.
• Assessment of trait responses to recent pollinator changes, including the addition of hummingbirds.

Main Results:

• Morphological traits exhibited higher heritability than nectar traits.
• Nectar traits, particularly sugar concentration, showed greater phenotypic plasticity than morphological traits.
• The proximal corolla section, regulating nectar access, displayed lower integration, correlating with rapid evolutionary changes.

Conclusions:

• Intrafloral modularity dictates variable evolutionary potential between floral morphology and nectar traits.
• Phenotypic plasticity in nectar traits, especially sugar concentration, contributes to differential trait evolution.
• The findings explain the observed rapid evolution of corolla morphology but not nectar in Digitalis purpurea populations.