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. 2024 Apr 18;19(4):e0300398.
doi: 10.1371/journal.pone.0300398. eCollection 2024.

Floral visitors of sesame (Sesamum indicum L.): Elucidating their nectar-robbing behaviour and impacts on the plant reproduction

Ujjwal Layek  1 , Trisha Bhandari  2 , Alokesh Das  1 , Prakash Karmakar  2
Affiliations

Floral visitors of sesame (Sesamum indicum L.): Elucidating their nectar-robbing behaviour and impacts on the plant reproduction

Ujjwal Layek et al. PLoS One. .

Abstract

Nectar robbing is common in angiosperms, especially in long tubular flowers or flowers with spurs that keep nectar out of reach of visitors. However, the robbing behaviour of bees is less understood. Here, we studied the sesame visitors, their robbing behaviour, and the impacts of robbing on plant reproductive fitness. Diverse insect species (primarily members of Hymenoptera) visited sesame flowers. The most effective pollinators were Amegilla zonata, Apis cerana, Apis dorsata, Apis florea, Ceratina binghami, Halictus acrocephalus and Xylocopa amethystina. Almost all visitors with variable percentages revealed the nectar-robbing phenomenon. Robbing activity depended on a complex of multiple attributes, including the visitor's body size, the corolla tube length, the availability and accessibility of nectar, and the resource-collecting task allocation of bees. Robbing activity varied according to flower-visiting species, flowering period and daytime. Robbing was comparatively higher in the late flowering period at 10.00-14.00 h. In the case of robbing visits, flower handling time was lower, and the visitation rate remained higher than non-robbing visits. Robbing visits did not significantly affect fruit and seed sets of sesame. Therefore, we can interpret the nectar-robbing interactions on sesame as commensal, with pollinators benefitting without altering the plant's reproductive fitness.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1
Flowers showing scars on corollae tubes made by (A) floral visitors and (B) artificially. Scale bars = 10 mm.
Fig 2
Fig 2. Daytime wise abundance of floral visitors of sesame.
Fig 3
Fig 3. Some visitors robbing on sesame flowers.
(A) Amegilla zonata, (B) Apis cerana, (C) Apis dorsata, (D) Apis florea, (E) Ceratina binghami, (F) Eretmocera impactella, (G) Graptostethus servus, (H) Halictus acrocephalus, (I) Scolia soror, (J) Thyreus nitidulus, (K) Xylocopa fenestrata, and (L) Xylocopa latipes. Scale bars = 10 mm.
Fig 4
Fig 4. Scatter plots showing relationship between visitor’s body sizes and robbing activity (%).
(A) body length vs. robbing activity, (B) intertegular distance vs. robbing activity of floral visitors.
Fig 5
Fig 5. The abundance (number of visitors/flower/10 min) and robbing activity (%) of visitors on normal flowers (i.e., control set) and pollen-less flowers having nectar content (data recorded at 7.00–8.00 h).
(A) abundance, (B) robbing visits of floral visitors.
Fig 6
Fig 6. The abundance (number of visitors/flower/10 min) and robbing activity (%) of visitors on normal flowers (i.e., control set), flowers with high nectar and pollen content, and pollen-less flowers with nectar content (data recorded at 9.00–10.00 h).
(A) abundance, (B) robbing visits of floral visitors.
See this image and copyright information in PMC

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