Bee pollination efficiency in watermelon (Citrullus lanatus) crops in Panama

•Quality of watermelon fruits produced on Panama crops increased with bee visits on flowers.•Flowers required a large number of visits to produce the best quality fruits, requiring at least 16 visits per flower.•The bee species depositing most pollen grains on the stigmas were Trigona corvina, Apis mellifera, and Nannotrigona perilampoides.•T. corvina contributed to the formation of more fruits, heavier fruits, and fruits with more seeds inside.•Bee Pollination efficiency didn’t seem to depend on the bee size, but on bee behavior. This study evaluated the bee pollination efficiency of wild neotropical bees visiting watermelon flowers in Azuero, Panama. We determined the quantity of pollen grains deposited on stigmas of excluded flowers by Apis mellifera, Nannotrigona perilampoides, Trigona corvina, Trigona fulviventris, and Lasioglossum spp. We also determined the number of produced fruits and their quality by weighing and counting the seeds inside the fruits produced by 1, 8, 12, and 16 visits of A. mellifera, N. perilampoides, and T. corvina. Finally, we calculated Spear's Pollination Efficiency Index. We found differences in the pollen grain number deposited by the studied bee species. On average, T. corvina deposited the largest amount of pollen (n = 379 ± 35), and T. fulviventris deposited the least (n = 86± 20). The fruit weight and seed number showed a positive correlation with the number of visits the flowers received. No differences were observed in weight and seed number in the fruits visited by the three bee species. The best quality fruits were obtained with 16 visits and no visit restriction treatment, with no differences between them. Our results show the studied bee species are capable of efficiently pollinating watermelon flowers, and have the potential for being used in the pollination of local crops. However, the best production results are obtained when the bee species act together.