Pollination efficiency of a single flower visit of Graphium angolanus Goeze (Lepidoptera: Papilionidae) on Psorospermum febrifugum Spach (Hypericaceae) at Dang (Ngaoundere, Cameroon)

Abstract

To determine the impact of Graphium angolanus on fruit and seed production of Psorospermum febrifugum, its foraging and pollinating activities were studied at Dang, from March 1st to 8th, in 2016 and 2017. For each cropping period, two treatments were set up through labelling of 100 to 200 flowers: one treatment made up of flowers that were protected then uncovered, exposed to a single visit of G. angolanus and reprotected; another treatment with at flowers protected then uncovered and reprotected without insect or any other organism visit. The foraging behavior and pollination efficiency of G. angolanus were measured. The fruiting rate, the mean number of seeds per fruit and the percentage of normal seeds of P. febrifugum were evaluated. The fruiting rate, the mean number of seeds per fruit and the percentage of normal seeds were evaluated. Results show that, G. angolanus foraged on P. febrifugum flowers throughout its whole blooming period. On flowers, individual of G. angolanus intensely harvested nectar. The mean number of individuals foraging simultaneously on 1000 flowers was 19, the mean duration of a visit per flower was 1.57 second and the mean foraging speed was 33.42 flowers per minute. For the two years, through the pollination efficiency of a single flower visit, G. angolanus provoked a significant increment of the fruiting rate by 47.95%, the mean number of seeds per fruit by 15.23% and the percentage of normal seeds by 26.32%. The protection of populations of P. febrifugum is important to maintain the butterfly G. angolanus in the environment so that it contributes to the plant covert essential for the conservation of biodiversity, and to improve fruit production and seed quality of this Hypericaceae.