I've been robbed! - Can changes in floral traits discourage bee pollination?

PLoS One. 2019 Nov 21;14(11):e0225252. doi: 10.1371/journal.pone.0225252. eCollection 2019.

Abstract

Some floral visitors collect nectar by piercing flower external whorls, acting as nectar robbers. They leave robbery vestiges, which can cause changes in floral characteristics, including physical and chemical signals that may influence flower recognition by pollinators. If pollinating bees associate these changes with absence or reduction in nectar volume, they can avoid these flowers, negatively affecting pollination. We aimed to investigate the effect of robbery on primary and secondary attractants. Additionally, we experimentally investigated if the visual signs present in robbed flowers affect the bee pollination of this plant species by discouraging pollinator visits. This study was performed in a very common pollinator-plant-cheaters system comprised by a bee-pollinated Bignoniaceae species and a nectar-robber bee that lands on the corolla tube and makes slits at its base during the nectar robbery. We experimentally isolated the effect of nectar consumption by this nectar-robber and investigated if the slits caused by the nectar-robbers affected the floral scent emission. In addition, we experimentally evaluated the effect of visual signs (slits) associated to the nectar robbery and the effect of nectar depletion on the pollination of Jacaranda caroba (Bignoniaceae). The robbers visited around 75% of the flowers throughout the day and removed significant amounts of nectar from them. However, the damages the robbers cause did not affect floral scent emission and we did not verify significant differences on pollen deposition neither when comparing flowers with slits and control nor when comparing flowers with and without nectar. We showed that even though nectar-robbers visually honestly signal the robbery and deplete high amounts of nectar, they did not affect pollinator visitation. These results showed that presumably antagonistic interactions might in fact not be so.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bees*
  • Behavior, Animal*
  • Brazil
  • Flowers*
  • Plant Nectar
  • Pollination*
  • Quantitative Trait Loci*

Substances

  • Plant Nectar

Grants and funding

This study was financed in part by the Grant 2018/14146-0, São Paulo Research Foundation to EG; Grant 446949/2014-0, National Council for Scientific and Technological Development to EG; Post-Doc Grant 2009/17611-7, São Paulo Research Foundation to EG and by the Coordination of Superior Level Staff Improvement, Brazil, Finance Code 001 to CVS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.