Mortality of stingless bees on Spathodea campanulata Beauv. (Bignoniaceae) flowers

Abstract

Spathodea campanulata Beauv. (Bignoniaceae) is a plant frequently employed in the ornamentation of public squares and gardens, attributed to its rapid growth and showy flowers. However, its use is controversial due to the potentially toxic nectar, which can lead to significant mortality rates among various stingless bee species in Brazil, posing a risk to native biodiversity and disrupting natural ecosystems. The aim of this study was to quantify and identify the species of stingless bees found dead within the flowers of the Spathodea campanulata plant. This investigation was conducted at the Ondina Campus of the Federal University of Bahia (UFBA), Brazil. Over a 15-day flowering period, 86 flowers from three specimens of this species were collected. After flower collection, the dead insects found within the flowers were extracted, stored, and identified at the Laboratory of Insect Bionomics, Biogeography, and Systematics (BIOSIS) at UFBA. The analysis revealed that all floral visitors were Hymenoptera insects, with 98.1% identified as bees (Apidae and Meliponini). In conclusion, S. campanulataflowers contain toxic compounds with insecticidal properties, leading to increased mortality among certain Melipona bee species. Melipona scutellaris and Apis mellifera bees are occasional visitors of the S. campanulata flowers; hence the lower mortality rates of these species. Given the damage caused by S. campanulata on native biodiversity, it is advised to avoid cultivating it in public squares, gardens, or in proximity to bee hives.