Pollination efficiency of Apis mellifera adansonii (Hymenoptera: Apidae) on Callistemon rigidus (Myrtaceae) flowers at Dang (Ngaoundéré, Cameroon)

To evaluate the impact of the honeybee Apis mellifera adansonii Latreille on fruit and seed yields of Callistemon rigidus R. Br. 1819, its foraging and pollinating activities were studied in Ngaoundéré for two seasons (June–August 2009 and July–September 2010). Each year, observations were made on 120 inflorescences per treatment. The treatments included unlimited flower access by all visitors, bagged flowers to deny all visits and limited visits by A. m. adansonii only. In addition, all flower visitors were recorded. The worker bee's seasonal rhythm of activity, its foraging behaviour on flowers, its pollination efficiency, the fruiting rate, the number of seeds per fruit and the percentage of normal seeds were recorded. Individuals from five and ten insect species that visited C. rigidus flowers were recorded in 2009 and 2010, respectively. Apis mellifera adansonii was the most frequent, followed by Myrmicaria opaciventris Emery. Apis mellifera adansonii intensely and preferably foraged for nectar. The fruiting rate, the number of seeds per fruit and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. Apis mellifera adansonii foraging resulted in a significant increase in the fruiting rate by 92.04% in 2009 and 64% in 2010, as well as the number of seeds per fruit by 38.67% in 2009 and 59.16% in 2010, and the percentage of normal seeds by 84.67% in 2009 and 82.30% in 2010. Cultivation of C. rigidus plants could be recommended to increase seeds, fruits and honey production.