Contribution of a single flower visit of Xylocopa olivacea (Hymenoptera: Apidae) on fruit and seed production of Roselle (Hibiscus sabdariffa L.) (Malvaceae) at Meskine (Maroua, Cameroon)

Abstract There a wide diversity of values linked to insect pollinators and pollination beyond agriculture and food production. To evaluate the impact of a single flower visit of Xylocopa olivacea on fruit and seed yields of Hibiscus sabdariffa, its foraging and pollinating activities were studied at Meskine (Maroua, Cameroon), in June 2018 and 2019. The experiments were carried out on 540 flowers divided into four treatments: protected flowers, bagged flowers, flowers protected and then exclusively exposed to X. olivacea and unbagged flowers, then reprotected without any visit of insect or some other life form visit to exclude the effect of hands manipulation. The bee’s daily rhythm of activity, its foraging behaviour and its pollination efficiency were evaluated. X. olivacea foraged on H. sabdariffa flowers throughout the plant’s blooming period. Among the 22 insect species recorded on H. sabdariffa flowers, X. olivacea was the most frequent insect with 40.89% of the 1670 recorded visits, and it intensely collected nectar and pollen. The fruiting rate of unprotected flowers was significantly higher than that of protected flowers (χ2 = 20.98; df = 3; P < 0.001). Through its pollination efficiency, X. olivacea provoked a significant increase in the fruiting rate by 49.98%, the number of seeds per fruit by 5.40%, and the percentage of mature seeds by 13.99%. Therefore, conservation of X. olivacea nests close to H. sabdariffa fields is recommended to improve fruit and seed production in this region.