Aphids reduce the attractiveness of female flowers to nocturnal pollinators

Aphid infestations Brachycaudus lychnidis em Silene latifolia negatively affect the attractiveness of female flowers to nocturnal pollinators, but do not impact male flowers. This is the conclusion of a study conducted by researchers at the University of Kiel in Germany, which evaluated the effects of herbivory on visual and chemical floral characteristics and pollinator behavior. Hadena bicruris.

Female plants infested with aphids experienced more pronounced declines in the number of open flowers and total floral biomass. Female flowers also emitted lower amounts of volatile compounds associated with pollinator attraction, such as benzaldehyde and lilac aldehyde. These changes did not occur in male flowers, which maintained similar levels of attractiveness before and after infestation.

Behavioral tests showed that female moths H. bicruris significantly preferred uninfested flowers compared to infested female flowers. There was no such preference for male flowers. Furthermore, female flowers produced a greater volume of nectar and a greater diversity of potentially bioactive metabolites, even under infestation, indicating a possible compensatory mechanism.

Researchers identified 41 volatile compounds in flowers and more than 4.300 metabolites in nectar, marking the first detailed characterization of the chemical profile of nectar in S. latifolia. The infection altered the chemical profile of the nectar differently between the sexes, suggesting specific defense strategies.

Although aphid loads were similar between female and male plants, only females exhibited a significant decline in floral attractiveness. This pattern contradicts traditional sexual selection theory, which predicts greater investment in attractiveness by male plants.

The results indicate that herbivory pressure can shape the evolution of floral traits differently between sexes in dioecious species. The study highlights the importance of considering tripartite interactions between plants, pollinators, and herbivores in both natural and agricultural contexts.

Further information at doi.org/10.1101/2025.07.22.666187