Increased reliance on diurnal pollination in a geographically and morphologically atypical sand verbena

Abronia ameliae visited by butterfly

By Jaeger et al.

Traditional pollination syndromes describe sets of floral traits that have converged based on pollinator selection. Closely related species are expected to maintain similar syndromes if pollinators remain stable over evolutionary time. However, deviations from ancestral floral traits may signal previously unrecognized pollinator shifts. Abronia ameliae (heart’s delight) presents a combination of traits typical for moth pollination — strong scented, tubular flowers — but also exhibits features unusual for nocturnal pollination, including pink, diurnally open flowers and large, upright inflorescences.

To investigate its pollination system, we conducted pollinator-exclusion experiments in both a natural population and a common garden, assessing the independent reproductive contributions of diurnal and nocturnal pollinators. Additionally, we characterized the floral volatile profile, which is an important trait in the attraction of many floral visitors. Our results indicate that A. ameliae is primarily diurnally pollinated, with visits from butterflies and day-flying moths leading to significantly higher seed set than nocturnal moth visits. However, nocturnal pollination still contributes meaningfully to reproduction, and the floral volatile emissions predominantly include compounds commonly associated with moth attraction.

These findings suggest that A. ameliae may have transitioned to a mixed pollination strategy, evolving traits that facilitate diurnal as well as nocturnal pollination. This shift challenges rigid pollination syndrome classifications and suggests the evolutionary flexibility of floral traits in response to changing pollination pressures.

Read the scientific publication in JPE